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Frequently Asked Questions

Check out our list of frequently asked questions.

Frequently Asked Questions

Check out our list of frequently asked questions.

Lucerne establishment

What is the time frame between lucerne stands and what is the reason for giving the paddock a break?
There is no set period required between lucerne stands but we usually recommend two years. This allows you to use the nitrogen that may have built up in the soil from nitrogen fixation by the lucerne for a grass or forage break crop. Options include a two year ryegrass or a cereal followed by a brassica that is fed off in early winter to then leave a late winter/early spring fallow. The fallow will store soil moisture before sowing a new lucerne stand in mid spring. But as always it depends.
 
Reasons for waiting two years before establishing a new lucerne stand in a paddock that was previously in lucerne include:
  • The older the stand the more likely old lucerne roots have built up chemical that inhibits the new stand growing- this is not always the case so you can go straight back into lucerne but there is a risk. How big this risk is and how prevalent in New Zealand with high winter rainfall no-one knows so some people ignore it and go straight back in with no problems. Others swear by two year breaks. This process is documented as about a 50 percent risk of autoalleleopathy (this is a fancy word the chemicals produced by the old lucerne stand building up in the soil and compromising the ability of newly sown lucerne seedlings to establish successfully). Work has been conducted overseas but has not been quantified in New Zealand. This autotoxicity, or if the older plants grab the soil moisture because they have developed their root systems, is also why you can’t really re-drill seed into an existing lucerne stand and expect it to be successful.
  • There is usually a reason a stand has thinned and needs to be re-drilled. Factors include weeds, pest damage, pugging etc. A two year break allows you to recreate a weed free environment and allows you to control browntop, couch/twitch, dandelions, mallow, horehound, thistles and other difficult weeds that can all build up as a stand ages and thins.
  • A two year break allows you to break any insect pest cycle that might also be building up.
Reasons not to wait two years:
  • If you have an establishment failure because of patchy establishment, blocked coulters, insect damage. Under these circumstances you can drill into the stand within the first 18 months to thicken it up. We don’t know how long you can go before the new seedlings will be suppressed by the older plants in the stand.
  • Patches drowned in a one-off ponding event have been successfully re-drilled into an older stand at ‘Bonavaree’. Note: if you have a patch in the paddock that routinely ponds in winter try filling it with a patch of balansa clover in the affected area with a bit of cocksfoot.
  • The old crop was relatively weed free and one year of forage break crops works – and you are prepared to accept the risk of autoalleleopathy.


My four-year old lucerne stand has a poor plant population. What should I do?

A low plant population in a relatively young stand can occur because the plants have self-thinned to a population that the soil can cope with – i.e. on stony soils a sparse population becomes evident quite quickly. If this is paddock is on a deeper soil then the population should still be high unless insects have taken some plants out.

So the first question is why has the population dropped? If it is poor soil then if you chose to overdrill lucerne any new plants will be out competed by those that are already there. If it was an initial poor sowing on a deeper soil then the problem should have been rectified earlier. If you lost plants as the result of water logging at some time through the winter then newly established plants may survive – as long as it was only a one off event.

We haven’t tried redrilling into a four year old stand so we don’t know what will happen. Some plants may survive and yes the older plants may produce a chemical that stops the new ones establishing but to be honest a four year old stand it is a grey area and we don’t know what the outcome would be.

If the lucerne paddock is on a deep soil with a good waterholding capacity some cover needs to be added or you will find weeds invade quickly and you lose the ability to salvage the stand.

An alternative to overdrilling lucerne is to drill in a grass to create a lucerne/grass mix - cocksfoot or ‘Bareno’ brome would be my recommendations. This approach may extend the life of this stand for 3-4 more years and the paddock becomes transition feed for ewes and lambs at lambing before they go onto straight lucerne. I would still treat the mix as a pure lucerne stand for grazing management.

 

What are our options for renewing flood damaged areas where lucerne died out?

If the area doesn’t flood in most years (i.e. flooding rarely occurs) overdrilling lucerne back into the damaged areas can be successful. This has been achieved in both Marlborough (at Doug Avery’s) and at Ashley Dene in Canterbury. Check out ourblog post to see how it worked.

If the area saturates in most years don’t bother trying to re-establish lucerne – it will drown at the next flooding. Landscape farm the area – choose the most appropriate species/mix to survive the conditions in an average year. In these areas you could try sowing 2 kg/ha of cocksfoot as the companion grass with:

  • 10 kg/ha balansa clover OR
  • 5 kg/ha of a yannicum type sub clover (e.g. ‘Napier’ or ‘Monti’) which tolerate wet soils plus 5 kg/ha of the standard sub clover varieties such as ‘Denmark’ or ‘Woogenellup’.

 

How important is initial weed control?

A well grown lucerne pasture is too much of an investment if not done properly – the longer it lasts the more cost effective it will be. To maximise investment it is important to get weed control in place before sowing/establishment.

Doug Avery uses two summer fallows to make sure no weeds seed. His lucerne is then direct drilled to stop bringing up new seeds from lower levels. He holds off planting even longer if weeds have not been beaten. Thistles are controlled by grub/spot spray so they don’t invade and reduce stand life. Weeds like horehound should be grubbed and targeted at all times whenever they are on the farm.

Annual weeds which germinate after sowing are usually shaded out by lucerne as the canopy re-establishes after its first grazing. At Lincoln University, we generally incorporate trifluralin prior to sowing lucerne while susceptible germinating weed seedlings absorb the product via the roots. Occasionally, and depending on the weed species that are present, we may apply a post emergent herbicide of imazethapyr (e.g. Spinnaker) and/or 2,4-DB to the seedling lucerne at the recommended growth stage.

In most cases, weeds like fathen disappear after the first year. If weeds are beating the lucerne at establishment you can hard graze the lucerne when it is about 15 cm tall, then leave it to flower before the second graze.

Over time invasion by perennial, taprooted or rhizomatous weeds (yarrow, dandelions, Californian thistles) occur because once a lucerne plant dies, it leaves a gap in the stand where weed seedlings can establish. Their presence should be an indication that the stand is nearing the end of its productive life. These stands can be over-drilled with grass and lambed on before going being targeted for pasture renewal which allows the difficult weeds to be controlled.

 

What is the latest recommended sowing date for lucerne on an unirrigated, light, stony soil?

It depends... Any time before Christmas is better than after Christmas. The key thing is weed control and hopefully getting some summer rainfall.  October would have been better because it gives the seedlings time to establish a bit and develop their root system before being exposed to water stress.

 

What determines how early I can sow lucerne on the sand country?

Soil temperature- once it is above 8°C and holding you can sow.

On sand country make sure you sow at 15-20 mm - no deeper - and into a firm seedbed that you heavy roll after sowing, preferably with rain due within 48 hours. With sand you may also want to put 20 kg/ha of N as Cropmaster 20 down the spout with sowing because sand has no nutrients and in this situation a little N at establishment may help lucerne get going – this is a unique situation that needs to be treated differently from anything else.

 

What is the best way to establish lucerne under pivot irrigation?

It depends on the soil type – either way irrigate before sowing to ensure the soil profile is full then drill. Do not irrigate again until the lucerne is all emerged and needs it. For a shallow soil (for example a stony Lismore soil) then don’t let the soil dry out and irrigate as required if the plants start to wilt after they are about 20 cm high.

For lucerne, one irrigation application of 50 mm is preferred over two of 25 mm. If you have a deeper soil then irrigation is probably not necessary at all for an establishing crop. The main thing is not to irrigate too often because the canopy is not fully expanded (i.e. full ground cover) so you will germinate weed seeds. However, keeping the plant actively growing is key – the more it grows the deeper those roots go. And of course let it flower or get to at least 40 cm tall before a first cut or graze.  An additional benefit of the less frequent irrigations is that you’ll reduce the humidity in the canopy and this can reduce the development of diseases which can thrive in warm, humid conditions.

 

Do I irrigate or let lucerne establish without irrigation this season?

There is no need to irrigate initially straight after drilling. You will just germinate a lot of weeds – but once the lucerne canopy has closed an application of water can aid growth and help roots explore the soil. The crop should be irrigated if it starts to get dry - this won’t stop the roots continuing to grow down the soil profile it will actually help them do that. The key thing is to ensure the soil profile had water before sowing. With spring sowing this is not usually a problem.

 

Fertilisers

Should I test for soil Aluminium levels and what depth should I take the soil sample?

Yes – in areas where aluminium is known to be a problem. Although aluminium testing is expensive in more marginal climates (like the high country), the upfront costs of rigorous soil testing are an investment in decision making. I would be looking to sample the soil down to at least 1.0 m because if the lucerne roots are not going down at least to that depth the purpose of lucerne is lost. We recommend taking a 0-15 cm test for your normal full soil test plus aluminium (Basic+sulphur+Al tests for topsoil layer). Then every 15-20 cm for just pH and Aluminium to 1.0 m – deeper is better.

Some farmers may have a pit or cutting on a road that could be sampled (provided it was cleaned back appropriately) but for others we have advised they get a digger out and go down up to 2.0 m if they can –then testing the lot but bulking samples from 1.0-1.5 m and 1.5 to 2.0 m (this way it adds only 2 extra samples for pH and Al).


Should I check magnesium and boron levels when soil testing?

These nutrients are important to check with soil tests if you think there may be a deficiency. Boron is usually readily available if your soil pH is between 5.7 and 6.5. Likewise magnesium is less plant available until the soil pH is above 6.0 – unless you know you are on a soil that is historically low in these nutrients then they should be available.

Boron is deficient on soils of high pH (7.0+) or those with low soil organic matter (e.g. sandy and pumice soils) so these will need checking with a soil test. Deficiency symptoms show up as a reddish tinge around the edge of leaves at the top of the plants.

Magnesium is deficient on soils of high potassium, or also sandy soils with low organic matter. Deficiency symptoms will show up as yellowing in older leaves between the veins mid canopy rather than at the top of the canopy.

So, if you are doing a regular herbage test because that is an efficient way of working out fertilizer requirements then Bo and Mg are probably not needed.

But...if you are doing a test to solve a problem on sandy soils or those with low organic matter they may be the issue. Molybdenum (Mo) can also be deficient especially when the pH is below 6.0 –deficiency symptoms will appear as yellowing herbage that looks nitrogen deficient (as does sulphur deficiency –which is most apparent after heavy winter rain).
In all cases, remember the lucerne is probably growing more herbage than previously so will place more demand on the soil, especially in a cut and carry regime - which is why grazing is always best.

 
When is the best time to take a herbage nutrient test in lucerne?

A herbage test in November (before water stress restricts growth), can aid in decision making if you think you have nutrient issues. At the time when lucerne growth is fastest, it is putting the most pressure on the soil to supply nutrients for growth. Therefore, any nutrient deficiencies will show up at this time.


For fertiliser, apart from soil testing, is there a basic requirement? 
No just do your testing. Annual soil testing should have been done in May – see txt alerts from Beef + Lamb New Zealand. For grazed lucerne apply just basic requirements to maintain the stand with an Olsen P in high teens. For cut and carry paddocks keep an eye on potassium (K) and for insurance do a herbage test if you want - take a sample of the top 15 cm of leaf and stem together for this. Do the herbage test when the plant is growing at its fastest to tell you if you have any deficiency.

 

What fertiliser should I use when sowing?

Depends on where you are. In Marlborough Doug applies 20 kg of nitrogen as Cropmaster 20. At Lincoln we don’t use any nitrogen but we always have the pH and P levels adequate at establishment for conventional cultivation.  If direct drilling superphosphate down the spout is key (see Kearny et al. 2010 for details). Don’t direct drill lucerne without phosphate.

 

Does lucerne require fertiliser nitrogen during its first season/ establishment to assist it with early development until it can fix its own?

Note: this question related to establishment of lucerne into land previously dominated by low fertility browntop, sweet vernal and hieracium. Two years of ryecorn crops were planned prior to direct drilling the lucerne with DAP at 100 kg/ha.

The planned use of the ryecorn crops and then direct drilling lucerne with DAP is adequate for the situation described here.

The high carbon from the browntop stubble actually needs to be broken down and to do that you need nitrogen – so if anything I would ensure the first ryecorn crop receives more N (urea) than usual – you may find that first crop has a lower than expected yield. This is because the N you put on for ryecorn crop growth has actually been used by the soil microbes to break down the roots and dead material from the high carbon browntop thatch. The “hoof and tooth” winter feeding then mechanically breaks that thatch as well and the concentrated number of animals adds N to the system from their urine which also helps it break down the remaining browntop. The second year ryecorn crop is usually higher yielding because of the first year N. Then in the third year of the pasture renewal phase the lucerne should be sown with only about 20 kg/ha of N and only because you are coming out of that N deficient period and are in a cold area (inland Canterbury). The DAP at sowing is ideal for that.

Let the lucerne grow in the first year until it is flowering – it needs to grow 5 tonne per hectare of root material underground and does that as a seedling. Make sure you freshly inoculate – especially on the virgin ground where there is no history of lucerne (in the previous 5 years). Seed coated within the 1-2 prior to sowing should be fine - after that ask for it to be freshly inoculated. The lucerne will use up any available soil N before it starts fixing N so you may not see nodules immediately.


Why is my young lucerne turning yellow in spring?

Note: this question relates to an inoculated 'Kaituna' lucerne stand at sown into a paddock with pH = 6.0* in autumn but symptoms can also be seen in established stands.

Pale yellow leaves can indicate sulphur deficiency. It is usually first seen as a yellowing of the young newly emerged leaves at the top of the growing stem and can often be confused with nitrogen deficiency.

If you've experienced a wet winter it is possible that sulphur may have leached from the soil. This can occur because sulphate (a plant available soluble form of sulphur in the soil) is a negatively charged nutrient and is repelled by the negatively charged soil. In a wet winter, soil water drains through the soil and the soluble Sulphate moves with it (however, it must maintain a neutral charge so it binds with positively charged ions such as hydrogen, potassium or sodium etc. in the process).

Do a herbage test now while the lucerne is actively growing - because deficiency symptoms are most easily identified when the plant is putting the most demand for resources on the soil system.

* for overseas readers: In New Zealand pH is usually determined in water not calcium chloride.


How much potassium do I need to replace if I cut and carry lucerne off a paddock?

In a cut and carry system you are removing a lot of potassium - about 20 kg/tonne of dry matter removed. If you take 3 cuts of 4.5 t/ha which would total 13 t/ha removed, you would need to replace about 260 kg/ha of potassium. On greywacke soils some potassium will come from the parent material but because there is limited grazing, you will need to keep an eye on the potassium levels from soil and herbage tests.

Weeds and Herbicides

What are the options for winter weed control in lucerne?

Answers kindly provided by Andrew Millar at CRT. View the document or look for the "Winter Weed Control Options for Lucerne" handout (9/5/2013) on the Field Day Handouts and Presentations page.

 

Is it necessary to spray established lucerne stands for weeds every year?

No, you don’t need to spray a stand every year if you are happy with the stand density.

Spot spraying areas where a weed problem is developing to prevent the rest of the paddock becoming contaminated is an option if the rest of the paddock is relatively weed free. However, we have worked out the cost of spray as being about the equivalent of 500 kg DM/ha. So if you think there will be 500 kg DM/ha of weeds by the end of spring it makes sense to spray them.

The issue is sometimes not what you can see now but what germinates in the spring. Under grazing it may be that the animals eat the seedlings while they are small but if left for silage or hay the newly emerging spring weeds may become a problem- so as always it depends and the final decision needs to take into account the type of weeds present and the final use for the stand (graze or cut).

 

How can I remove the weeds without damaging autumn sown lucerne in spring?

First, why did you sow in autumn? It is seldom as successful as spring sowing. To remedy graze the paddock to remove lucerne leaf area.

If you have a good plant population from your autumn sowing herbicide may not be necessary if the majority of weeds are spring annuals – they won’t recover from grazing and should be shaded out as the lucerne reforms its canopy after grazing.

If the lucerne population is ok (but not great) it will still come through - but slowly. Wait for the paddock to refresh (2-4 days after grazing) and then spray for broadleaf weeds. 

For stands with poor populations following sowing – these can be thickened up by overdrilling with more lucerne. Hard graze, immediately overdrill and herbicide 2-4 days later (non-residual and herbicide application should occur before newly overdrilled lucerne emerges)

BUT….autumn establishment of lucerne should be avoided if possible because it takes at least 18 months to catch up with where you’d be if the stand had been spring sown. An annual forage followed by spring sowing is preferred for successful lucerne establishment.

 

How do I control dandelion (Taraxacum officinale) in my lucerne?

Dandelions are taprooted weeds that compete with lucerne for water and nutrients. Their numbers increase as the lucerne stand ages, although chemical control is now possible.

In mid/late Autumn after a clean-up graze, dandelions can be sprayed with metsulfuron at a low rate (5-8 g/ha), but this chemical will knock the lucerne. Talk to your chemical representative before using it.

 

How can I control docks (Rumex obtusifolius) in my lucerne?

Asulox (a.i. = asulam) kills docks – it is able to be used on lucerne in autumn when the docks are still actively growing. Application after a 20+ mm shower of rain that breaks summer dry periods is ideal. The use of lucerne/grass mixes can complicate things but Asulox is also registered for established pasture. For both lucerne and pasture a period of 2-3 weeks of active growth after cutting or grazing is recommended before spraying. Check with agents for product and water rates. Docks have a deep tap root and therefore compete with lucerne so control is important where possible.

 

How do I control horehound (Murrubium vulgare) in my lucerne?

A grubber in the truck and ever vigilant staff are the most common methods of horehound control. Make sure you clean-out any new patches anywhere on your farm because the seeds will become lodged in the sheep’s wool and be transported into your lucerne paddocks. Where grubbing is impossible some success has been gained using Roundup 490 at 750ml/ha, with 10 grams of metsulfuron/ha as a spot spray. This is definitely off label and is used at the owners risk. In the field comments suggest if you can spray onto wet horehound (i.e. in morning after frost) it is most effective. We at Lincoln University have no experience of this combination to date so are reporting this information without any experience – happy to add comments from anyone who tries it and is successful or unsuccessful to add to the knowledge pool. (Leave us a message by emailing a member of the Dryland Pastures team via the “Contact us” page).

 

What is the best herbicide to control grass weeds in a lucerne stand?

Paraquat and atrazine are the standard chemicals used but there are lots of options including  products containing haloxyfop-P (e.g. Gallant) to control grasses in lucerne monocultures.

 

How do I control wild plantain (Plantago lanceolata) in my lucerne?

Doug Avery responded that he controls plantain at ‘Bonavaree’ during their normal winter spray programme which is Gramoxone (a.i. 250 g/litre paraquat) and atrazine. Alternatively, after heavy grazing (no lucerne leave surfaces to intercept the spray) use 2,4-DB. The preference would be for this to occur in spring not autumn - the lucerne crop may be suppressed (less feed than expected in the rotation following the application) but spring application will allow time for the crop to grow out of it in the subsequent rotations.

 

How do I control mallow (Malva spp.) in my lucerne?

Products containing flumetsulam as the active ingredient (e.g. Preside) can control young mallow (< 4 leaves), but weeds must be actively growing to get a good kill. As with most weeds, the herbicide is more effective on young weeds in comparison to older established weeds. For older mallow the best control is with a grubber. However, some farmers report that imazethapyr based products (e.g. Spinnaker) will stop young mallow plants from producing seeds which can contaminate lucerne seed crops.

 

When should I spray mallow (Malva spp.) and nodding thistles (Carduus nutans) in a lucerne stand?

Mid-summer rainfall provides an excellent opportunity, while temperatures are warm, to use herbicide on difficult perennial weeds that may be affecting older (3 years +) lucerne stands.  E.g. Mallow (Preside, a.i. flumetsulam) and Nodding thistles (Velpar DF, a.i. hexazinone).

As always, check the product labels carefully for details and apply as recommended. Spray after grazing when lucerne leaf is minimal.

 

How can I control scotch thistle (Cirsium vulgare) in my lucerne stand?

In most cases we avoid using expensive herbicides such as Velpar DF ($150 -$200/ha). However, we do use such chemicals were the lucerne establishment is under threat and Velpar is a very effective option for various weeds but it can cause damage on young lucerne stands. I would recommend paddocks be inspected first by experienced agronomists before committing to this option.

People also report success with a well maintained and calibrated weed wiper or wick boom. Directly after grazing (when the lucerne is below thistle height) applying Metsulfuron (Associate/Zeal etc) @ 2-3 g/litre water with a slow double pass (East-West/ North–South) ensuring that the boom is totally saturated with the mix before starting. This option is widely used and is very cost effective. Some farmers have also reported success with using 2L/ha of MCPA on young lucerne (10-15 cm high). This also controls fathen and other broad leaf weeds.

 

How can I control stinging nettle (Urtica urens) in lucerne?

Stinging nettles will be eaten by sheep if they are topped – the animals will then happily graze them. If a chemical option is required Basagran (a.i. 480 g/litre bentazone) or 2,4-DB should get them as seedlings (not mature established plants). Apply after grazing, when the lucerne canopy has been eaten off (less lucerne surfaces to put chemical on and better access to the weed leaf surfaces). Weed wiping with a stronger chemical, like 2,4-D will also work but only wiped with a calibrated and high quality wiper following a hard graze of the lucerne - it will kill the lucerne if you make contact/drip the chemical on the plants.

 

What can I spray on my new lucerne to control wireweed (Polygonum aviculare)?

Two suggestions - although we have no experience with either chemical on this weed;

  • Preside or equivalent (a.i. flumetsulam) is reported to provide reasonable control as a seedling and should be used in warm conditions after summer rainfall.
  • Equate (a.i. imazethapyr) is reported to control wireweed when applied to lucerne at the two leaf stage or later.

Pests and Diseases

Are aphids a concern when cutting lucerne for hay?

Aphids are not a concern when cutting hay but….don’t feed that hay to ovulating stock in autumn - see our previous blog onovulation for details. Aphids at high numbers can make the lucerne unpalatable to stock and elevate phytoestrogen levels so beware of the end use of the hay. Also, as they are cut the aphids can drop onto the newly emerging shoots and significantly reduce the regrowth of the following crop through direct damage and the introduction of a virus. If levels are damaging an insecticide spray is recommended.

 

Does wireworm affect lucerne?

We don’t know! We have searched our resources and asked some of the local entomologists and none can remember ever seeing wireworm attack a lucerne stand. But it is highly likely they will attack young seedlings because they are not that selective at feeding so will eat young seedlings of most things. My entomologist tells me seed treatment is likely to take care of the problem but he’s not sure! So we get two out of 10 for that answer – sorry  we can’t be more authoritative.

 

How does clover root weevil affect lucerne?

Clover root weevil (Sitona lepidus) has minimal impact on lucerne as far as we know – work at AgResearch has indicated a preference of the root weevil for white, red and Caucasian clovers with minimal impact on lucerne. Just another advantage of using the world’s most important pastoral legume.

In contrast, Sitona weevil (Sitona discoideus) does affect lucerne and control was achieved in the 1980s by the introduction of a parasitic wasp. This has probably been the most successful biological control programme developed in NZ. Occasional outbreaks of Sitona weevil can occur but like most insect outbreaks they tend to follow a boom bust cycle and the parasite keeps numbers to levels below an economic threshold most of the time.

The third weevil to watch is white fringe weevil (Naupactus leucoloma) – this can cause economic damage and there is no chemical control option. For white fringe weevil cultural control methods are avoiding grazing until last in a rotation (they move attached to wool and machinery), direct drilling grass into infested paddocks (it reduces their reproductive ability) and cultivating starlings (a less popular biological control agent).

 

What is the cause of yellow leaves with purple black dots over a whole young lucerne plant?

Without seeing the plant it is difficult to know. However, if it is a single plant in the stand it is likely to be insect damage whereas if if it covers an area of the paddock it could be a nutrient deficiency. It may also be a fungal issue which typically occurs in warm and humid conditions. Sending the sample to Plant Diagnositics Ltd could give a diagnosis.

 

One of my established  lucerne paddocks has come up very patchy this year. What could have caused this to happen?

It is difficult to know what has caused the problem without seeing it – there are several reasons.

It could be eel worm also known as stem nematode (Ditylenchus dipsaci). If so it will eventually take over the paddock – (over the next few years rather than in a season).  This would be most common if you have sown 'Wairau' as the cultivar. Most of the other cultivars (e.g. 'Kaituna') have been bred with resistance. For a confirmation of this you could take a sample and send it to Plant Diagnostics Ltd.

If it is stem nematode there is not much you can do about it. Try to avoid making hay from this paddock and carting that hay around – the nematodes live inside the stems and there is no viable chemical control which is why resistance is bred into them.  The symptoms are usually short stunted internodes (which you seem to have with the stems shorter than the rest of the paddock) in patches and they tend to spread in the direction of any water movement and out in a circular pattern.

Other causes of patchy growth in paddocks that previously grew well include if this is where water ponded during the winter and there is some soil compaction that is restricting root growth or has caused some death of the root systems.

As for slugs – yes they can be a problem mostly in a wet spring and especially if the paddock was direct drilled. Slug bait should take care of the problem.

 

Lucerne Management - Plant

When can I heavy roll my lucerne without damaging the stand?

Generally late winter (early/mid-August depending on region and winter activity of the cultivar), when stems are short and soft and are ideal for rolling in surface stones. At this stage the stems are usually soft so if they bend they will usually stand back up. If you are unsure, walk across the paddock and see if you are breaking any shoots off. If you leave it too late the stems harden up as they grow and if rolled, they will break off. These shoots die and therefore new stems have to be produced. This delays spring growth.

A second option is to roll immediately after the first spring grazing before the topsoil dries out.

 

Does frost have the same effect as late grazing on lucerne?

It can but it depends on the timing and the severity of the frost.

As autumn progresses lucerne progressively is able to cope with some light frosting and will keep growing (it adapts to the decreasing temperatures from autumn into winter). However, a hard frost (and we don’t know exactly what level that is) will kill the growing point at the top of the plant. Once this happens the plant cannot keep producing leaves and growing up. This means it will stop gaining height. At the same time the herbage may go black or brown and begin to die. Because the growing point is dead the plant will then start to try and regrow a new set of shoots its base.

If you have had a frost or the herbage starts to look spotted, brown and is dying – quickly graze it all off with a large mob and try to avoid crown damage. This also reduces any population of overwintering aphids and lets the sunlight hit the base of the plant to encourage those new shoots to begin again ready for spring growth.

Once a stand gets to 4-6 years old you can start to see a build-up of dead stems - from grazing and winter die back. Running a set of chain harrows over the stand to knock off some of these old stems can allow new shoots to grow and thicken up the stems.

 

When can I start grazing my lucerne in spring?

No matter where you are, you can begin spring grazing when your first paddock is 15-20 cm high.

 

What stocking rate should I use for spring grazing of lucerne?

Stock lucerne at about 12 ewes with twin lambs per hectare. So if you have 20 hectares of lucerne that will be a mob of 240 ewes and twins on the first paddock of 4 hectares.  Put them on about two weeks after lambing when lambs are just starting to have a green pick and the lucerne is about 25-20 cm tall.  See the Practical Lucerne Management Guide (PDF 576 KB) for details of subsequent stock movements around the paddocks with an aim to be back at the first paddock in around 35 days.

Be prepared to adjust stocking rates throughout spring. Warm wet conditions may allow higher stocking rates or the opportunity to drop a paddock out for hay or silage.

Post weaning, stock at 20-25 lambs per hectare provided spring rainfall has allowed lucerne regrowth. It is more efficient for total liveweight gain to give fewer lambs a total diet of lucerne for 6-8 weeks than many lambs lucerne for 2-4 weeks.

 

Is it possible to lamb ewes on lucerne or will it damage the stand?

Set stocking is not ideal for lucerne but as long as the stocking rate is low enough that the lucerne is growing ahead of the consumption (getting taller with animals in the paddock), lambing on lucerne for 3-4 weeks in spring may be ok. After this, start moving the mob with lambs at foot on a rotational grazing cycle through the other lucerne paddocks. Return to the set stocked paddock as the last in the sequence, after allowing about 35 days regrowth.

Lambing on a paddock which has been oversown with some grass or on an older runout paddock is recommended (this allows the rumen time to adapt). Most farmers find they can start rotationally grazing the mob when lambs are 10-14 days old because mismothering is rare. Ewes that are accustomed to lucerne tend to walk to the next paddock knowing they will get a decent feed. Any mismothered lambs actually eat high quality feed anyway- compared with grass pastures where the ewes target the clover before the lambs can get to it.

At Ashley Dene, we are currently (2012/13) running an experiment looking at the effects of early spring set stocking, and hope to be able to come up with specific answers and potential management practices for farmers in regard to set stocking during lambing.

 

How detrimental is it to lamb very low numbers on lucerne/cocksfoot mixes?

Our recent work at Lincoln suggests you could stock at about 8 ewes+lambs/ha for 3-4 weeks (tailing?) and not cause too much damage on a lucerne stand but...

The key factors are:

  • The lucerne should be growing ahead of the intake so that the lucerne is getting taller while the ewes and lambs are in the paddock (start when lucerne is around 10-15 cm tall)
  • Spring lucerne growth should see the crop grow taller over the first 2-3 weeks until intake of lamb increases and
  • Once the feed supply starts to drop below the intake (mean lucerne height starts to decline) increasing stocking rate to eat all of the herbage within 3-5 days and (so in total you have been on the lucerne 3-4 weeks)
  • Start your usual lucerne rotation of six paddocks
  • This practice is becoming necessary as people increase the area of lucerne on farm and the lucerne grass mixes are an ideal place to start the rotation
  • Make sure the paddocks managed this way get extensive flowering in autumn to recover from the spring set stocking and then
  • Don’t use those full flower stands for mating.


Defining this practice is on-going at Ashley Dene with the aim of further increasing flexibility in lucerne management at this crucial period. We are planning on stocking our set stocked versus rotationally grazed experiment this week with ewes and 2 week old lambs.

Update Summer 2014: Guidelines are now available on our Dryland Pastures Blog.


What is the recommended stocking rate for weaned lambs on lucerne?

The rate for grazing weaned lambs depends on size (and hence feed requirements) in relation to lucerne  growth and rainfall which influence feed supply.  A good starting rate would be 20-25 weaned lambs per hectare - see our website for details.

 

Should I leave a 10 cm residual when grazing lucerne or lucerne/cocksfoot mixes?

As always there is no right answer- it depends. If the lucerne is high quality feed eat it. To find out squeeze the lucerne stems when you go into the paddock. If they are soft all the way up (which usually only occurs when the crop is less than 25 cm tall) then the lucerne is all high quality feed. If you can feel the woody base that is tough/hard graze down to that point. The herbage above the break* has an ME of 12 MJ/kg DM and crude protein of at least 24 percent. The lower stem has an ME of 8 and crude protein around 12 percent. (See below on how to do your own 'break test').

For lucerne/cocksfoot mixes the cocksfoot is probably as palatable as it will be in spring so it can also be grazed hard. But overriding this is the stock requirements. In spring stock should be the priority so if that means leaving a higher residual to maintain control of the lucerne paddocks three to four ahead then leave a higher residual and clean it up in the next round or later in summer. Alternatively think about dropping out paddock six if it is getting too tall (over 40 cm). This can be conserved.

Some farmers are happy to leave cocksfoot ungrazed but hammer it with ewes post weaning. In this leader/follower system the lambs have the first few days grazing  and the ewes follow but in total still only 10 days on at a maximum.

Any residual lucerne left behind may help the next set of shoots grow but it is not imperative to do so in ideal growing conditions in spring. So make your call based on the animals at this time of year – in autumn the answer is plant dependent.

* To conduct a 'break test' on lucerne stems:
Cut a stem (take one to five stems of average height for the paddock about to be grazed) and cut them off at the base. Grasp the tip gently and pull it downwards so it bends over to the point at which you cut it. If it doesn't break it is all soft, young high quality feed. For the taller stems you will find they 'break' when bent downwards. This point on the stem is the point where the stem becomes woody/tougher and stem material below this point is of lower quality.

 

How do I irrigate my lucerne with a pivot?

Rule of thumb: no leaf = no water used...so don’t irrigate or your get weeds.

a)      Timing
Essentially irrigation of lucerne is about lots and not very often compared with white clover which is little and often. So if lucerne has been grazed or cut the leaf has been removed and the crop has stopped using water so there is no transpiration. It doesn’t need water immediately after grazing or cutting and irrigation at this time will only germinate weed seedlings and encourage them to grow. Leave irrigation until about 7-14 days after grazing when you can see the new shoots about to spread their canopy. These are then able to use the water and will dry the soil surface out desiccating any new weed seedlings and shading them as well.

b)      Amount
The deep taproots of lucerne mean it is best to apply water infrequently in a large amount. i.e. Rather than one pass of 20 mm every week for three weeks – three passes of  20 mm over three days is preferred. This allows the soil water to infiltrate down the profile below the weed root zones.  The lucerne will then start using the water closest to the surface again and dry out the profile and out compete weeds.

c)       At establishment – seedling crop
Lucerne grows its roots at about 10 mm per day once it has started to grow. Ideally a spring fallow has ensure the soil profile is full of water. Alternatively, ensure field capacity before sowing so the soil isn’t capped once sowing occurs.  Then leave the crop to get on with growing. The roots will rapidly explore the soil so that if there is 60 days of growth before the crop needs cutting the roots will be about 60 cm down the profile.  In season rainfall can assist the process but frequent irrigation at this time will only lead to weeds.  In extreme dry, if the crop looks like it might die, an irrigation may be required before the first cut/graze at bud visible for this seedling crop. Otherwise leave it to grow and then follow the rules above on irrigation once the canopy recovers.

 

I’m applying for irrigation rights. What pasture will give me the best return for the cost of the irrigation?

There is no right answer to the question of what pasture to grow. Many dryland farmers in the South Island are now working out that the only way they can make money off irrigation is to consider it an investment for their children or grandchildren or to only use it strategically to finish their lambs. Most full conversions go into dairy sooner or later and even they struggle if they have paid too much for the water. Where only limited irrigation is available it is likely to be hugely beneficial to assist finishing your own stock - provided you can manage irrigated pastures with lambs – this has its own challenges compared with a dryland system.

Lucerne is probably the highest yielding pasture under irrigation but how to irrigate changes. The economics of each stock class will vary over time but one option is to continue with a breeding flock and finishing more lambs on lucerne while buying in bulls. This mixed livestock system is being successfully implemented on many dryland properties we are involved with. The advantage is bulls are more gentle on the plant and can be easily sold if things go dry. Most people who have irrigation spread it over a larger area than can be fully irrigated at all times so again the lucerne helps due to its deeper taproot and ability to maintain growth for longer in between irrigation events. It has a longer return rate than pasture because of the depth of root.

In irrigated systems (or those where rain is adequate for growth) the key to yield is actually nitrogen not water.  So if you grow grass you will need to apply over 400 kg N/ha to maximise yield.

As a guideline to help:
Lucerne will produce roughly 25 kg of DM per mm of water per hectare that it uses (Note: this is water used by the plant not water applied – the efficiency of this relative to water applied will depend on the irrigation system, drainage etc.). So if you have 1.0 ha and it uses 200 mm of irrigation it will grow an extra 5.0 t DM/ha compared with what you are currently growing. This calculation assumes you have summer dry conditions that restrict pasture growth for at least 6 weeks of the year.  Because lucerne is a legume it is seldom nitrogen deficient so it uses that water relatively efficiently. You can expect a similar response from a ryegrass pasture if you irrigate but it will need at least 400 kg N/ha to get that type of response as it can’t fix nitrogen from the atmosphere.  In high yielding regions the amount of N required to maximise yield is economically and environmentally prohibitive. We’ve shown both a ryegrass and cocksfoot based pasture at Lincoln under irrigation required 600 to 800 kg N (not urea) per hectare in total. So, in a cut and carry system, to fully utilise your water with pasture you would need to apply over 1 t/ha of urea. Check out the results for cocksfoot (Mills et al. 2006) and ryegrass pastures (Black & Murdoch, 2013) published by the New Zealand Grassland Association.

Our research has shown that grasses can use water as efficiently as lucerne but need a lot more N than is currently applied (or is permitted to be applied) to do that. All irrigated dairy farms in Canterbury are nitrogen deficient - every spring you can see the effects with urine patches prominent in the paddocks. The key factor limiting growth is not the water - it is the nitrogen. So the addition of irrigation water to pasture by itself is actually not helpful. Water added to resident pasture is likely to produce about 8 kg DM/ha/mm used. The grass is usually nitrogen deficient all year. When the canopy of the pasture is closed, N deficient grass and grass pastures non-limited by N deficiency use the water at the same rate. However, the pasture with sufficient N will grow twice as much dry matter as the N deficient grass pasture. So a fully N fertilised grass pasture (which you won’t be allowed) can also give you 25 kg DM/ha/mm of water used.

In Canterbury calculations for water allocation are done on the basis of 20 kg DM/ha/mm of water used. This would be for a well fertilised ryegrass/white clover pasture. But there is little white clover in most Canterbury pastures so many farmers just add urea as it’s easier. The cost of nitrogen is directly related to the cost of natural gas so if natural gas price goes up so does the cost of urea.

In work here at Lincoln we found:

  • 6 t DM/ha per year for dryland cocksfoot – (eight year old 'Wana' stand)
  • 10 t DM/ha/yr for the same pasture but fully irrigated (wouldn’t cover the costs of conversion). This increased yield 66% compared to the dryland unfertilised cocksfoot.
  • 15 t DM/ha/yr for the same pasture but fully N fertilised. No irrigation applied and yield was increased 1.5 times more than the dryland pasture and 50% more than by only applying irrigation to an N deficient system (which is why we push legumes including lucerne so hard for dryland farmers).
  • 22 t DM/ha/yr for the same pasture with full water and full nitrogen – cocksfoot grew as much as ryegrass. The yield was more than double that of the pasture getting only irrigation.

Lucerne (either irrigated or dryland) is your best bet to produce DM per mm of water available and the advantage is greatest in the warmest areas.

 

It’s early December and my lucerne crop is water stressed, wilting and leaves are dying. Should I graze/cut now or leave it until it flowers?

Either graze or cut the lucerne now. If no decent (>50 mm) rainfall is expected in the immediate future the longer you leave it the more leaf will drop off and the lower quality the standing feed will be.

Flowering is not important at this time – it is important to allow flowering at some point in late summer/autumn. After the longest day lucerne perceives the days to be getting shorter, this triggers the plant to start prioritising reserves down to recharge the root reserves it used for growth in spring. This ensures the lucerne is in the best state.

 

What is the recommended stocking rate for weaned lambs on lucerne in late December?

The stocking rate will ultimately depend on the size of the animals (animal demand) and your lucerne growth and rainfall (feed supply). About 20-25 weaned lambs per hectare available is a starting figure. We recommend that you adjust the mob size as required to complete grazing a paddock in five to seven days (no longer) running a six-paddock rotational grazing system. If your lucerne is getting ahead of you close one of the paddocks for conserved feed (choose a different one every year & remember to replace the nutrients you’ve taken off – check the Fertiliser FAQ Section on requirements).

 

Does spelling lucerne in early January have the same benefit as spelling in February?

The simple answer is yes. If it is convenient to spell lucerne in January then that is great do so and it will be as useful as later in February in recharging root reserves for early growth next spring - provided the lucerne is actively growing during the period it is spelled.

The more accurate answer as always is it depends. Remember flowering lucerne, or lucerne infested with aphids, can cause problems if used as a flushing feed. Think about the time of spelling in relation to other feed requirements over the next few months. If you can let it flower in January and then use that mature feed for finishing lambs or making hay/silage that is fine.

The aim is that the regrowth of clean stands (aphid and leaf disease free) in autumn should be fresh and able to be used for flushing. If you have no other feed available because things are dry then think about how you can present ewes with quality feed at flushing – lucerne regrowth about four weeks old would be ideal.

 

Why are there dark green patches in my lucerne paddock?

In newly established lucerne: New lucerne stands tend to rely on soil nitrogen reserves rather than “paying” rhizobia to fix atmospheric nitrogen into a plant usable for them. This is because the plant has to supply carbohydrate to the rhizobia bacteria whereas the uptake of soil nitrogen, when available, doesn’t cost as much in energy terms. Once the soil nitrogen is depleted – or when the supply is insufficient to meet the plant demand during active growth then it will start paying the rhizobia.

In an established, but water stressed, lucerne stand the green patches are most likely to be urine patches. Established stands have usually depleted the freely available soil nitrogen and are relying on the rhizobia bacteria to supply their nitrogen requirements. As the soil dries the plant grows less and therefore the need for nitrogen from the rhizobia decreases (basically there’s no point in paying for something the plant doesn’t need). However, if the plant is able to respond, the urine patches from grazing animals increase the soil moisture and freely available nitrogen in the urine patch. The plant can use this moisture and nitrogen for growth while the surrounding areas are still water stressed. Also because there is nitrogen in the urine the moisture available for growth in that patch will produce more dry matter for the water used than the surrounding areas (because nitrogen deficient crops/pastures don’t use water as efficiently as crops with sufficient nitrogen for growth).

 

Why have the roots of my lucerne plants reached a certain depth and then turned horizontal?

This suggests localized aluminium toxicity – the horizontal roots are a classic example of aluminium in a sub soil (see photo below). This is one reason we advocate soil testing to 15 cm and then again from 15 to 50 cm if possible. This will allow the subsoil concentration of aluminium to be determined. Values above 3 mg/kg soil are considered harmful to lucerne and cause the horizontal root growth. If during the dig you find you have several lucerne roots gong straight down this suggests the aluminium is quite localized in patches in the soil. This is a major problem in some areas of the high country and Central Otago.

 

Effect of aluminium toxicity – lucerne roots growing horizontally at Lees Valley, Canterbury (17/1/2008).

 

An application of lime before ploughing will allow soil a change in soil pH down to ploughing depth. This will ensure the aluminum becomes plant unavailable. However, the progress of the effects of lime down the soil profile is extremely slow. It can takes several years to move 5 cm. Shallow lucerne roots are less of an issue in a high rainfall environment where frequent rewetting occurs- here weeds are more likely to be a problem. In drier environments the horizontal roots prevent the lucerne accessing soil water at depth and limit the potential production from the system. Lucerne roots are more susceptible to aluminum than most other legumes.

 

When is the best time to overdrill annual ryegrass into my runout lucerne to extend stand life and what herbicides are required for weed control?

The decision to extend stand life of a runout pasture depends on the weeds which are present. If the stand is running out then using a short term ryegrass is a stop gap- sow as the season allows in autumn after a hard graze of the lucerne. The annual ryegrass will overtop most weeds and outcompete any establishing winter annuals like barley grass, Poa annua and chickweed (Stellaria media) so they shouldn’t need chemical control. 
Then the issue is timing of stand renewal – if you are going to plough next spring again why worry about the weeds? Deal with them in the intervening crop phase. This is assuming the weeds are not horehound –which must be dealt with on a continuing basis (see FAQ on horehound control in the Weeds & Herbicides section).


Lucerne Management - Animal


When should I vaccinate livestock grazing lucerne?

In Marlborough Doug Avery says “We give our lambs their first vaccine at weaning or soon after. Then a booster is given at about 6 weeks after weaning. From then on we give it just before lambing to the ewe once a year. This year lambs at 'Bonavaree' are also getting a B12 injection at tailing."

 

How important are vaccinations for livestock grazing lucerne?

The main issue with sudden death of fast growing animals is the cause of the death. This may be caused by clostridial bacteria – the bacteria use the sugar in the rumen to multiply in number quickly and overwhelm the animals. However, they also multiply quickly after death so the vet usually can’t tell if the  infection was before or after death when making a diagnosis.

Step 1:
The first issue is that whatever vaccination programme you are using must be up to date and timely. With fast growing animals they may need a booster earlier than slower growing animals. So step one is make sure your current vaccination programme is up to date and timely. Many people use five in one and are having no problems. Make sure the final pre-lamb vaccination is at least two weeks prior to lambing so that the vaccine has time to get into the colostrum before lambing. This ensure maximum effectiveness for the lambs immune system from birth.

Step 2: 
There are several strains of clostridial bacteria - seven of which are found in NZ and covered by the ten in one vaccine. The ten in one is offering protection from two additional strains than the five in one. However, there is debate about whether these extra two have actually been found to be infective and a problem in sheep. It depends on which vet you talk to as to which answer you get.

So, Step 1 would be the prudent course – make sure your current programme is up to date and on time – keep an eye on rapidly growing animals and vaccinate them. Some farmers swear by 10 in 1 – but it may be that the extra cost is making them more vigilant on getting their timing right and giving boosters when needed.

 

What can I do to reduce the risk of red gut when grazing lucerne?

Ensure there is fibre (hay) and salt available at grazing and particularly when the lucerne is lush or after heavy rain. On occasion some farmers also report success from wilting lucerne in front of the grazing. The stand my have some strips cut in it about 48 hours before shifting stock onto the Lucerne (see photo below). Red gut is related to the twisting of the intestinal mass on sheep usually grazing lush pure lucerne and other lush pastures for at least a week. It may also occur 4-6 days after rain particularly in summer and autumn after dry periods. Weedy lucerne or lucerne with meadow hay available is less likely to results in red gut. Weaned lambs going onto lush lucerne are susceptible hence the move to have ewes and lambs grazing lucerne in spring. As with bloat, avoid putting hungry animals onto lush feed including lucerne.


Example of cutting strips in lucerne prior to grazing to wilt a proportion of the feed on offer at 'Bonavaree', Marlborough. Photo provided by Doug Avery (5/10/2015).
 
 


How important are B12 injections for livestock grazing lucerne?

B12 injections are used to overcome cobalt deficiency. Most animals ingest some soil when grazing pastures and this is where the majority of cobalt needed to meet animal requirements comes from. The cobalt from the soil they eat while grazing stays in the rumen and makes cobalt available. However, if animals are grazing a taller stand/pasture and never putting their head down to graze near the soil surface then their intake of cobalt can be lower than usual. On occasion cobalt deficiency may show up in areas where it wasn’t traditionally used. B12 infections are a simple and effective way to minimise this concern.

 

What causes scald in my brassica or lucerne and how can I avoid animal health issues?

Rape scald generally occurs when stock graze “immature” crops of rape in summer. “Immature” is actually not an agronomy term – what it actually means is there are high levels of nitrogen in the leaves that are not yet formed into structural or metabolic proteins. This often occurs early in the crops life because soil N levels are high because of mineralisation after full cultivation before sowing or the use of more than about 40 kg N/ha at sowing.

When nitrogen levels in the plant build up stock can’t cope with the high N levels in the ingested feed. Chlorophyll or other N based compounds get into the blood stream – this makes animals photosensitive. And hence regions with high exposure to the light and little wool covering are most sensitive (e.g. ears and face) effectively get sunburnt. The protein rich feed also enables them to eat without much foraging so the natural process of movement that would exert energy and allow waste from the blood stream to be removed also doesn’t happen.

Other complications with brassicas come from the use of sulphur based fertilizers- so these are not recommended for brassica crops but if cobalt or copper are limiting direct application (foliar or direct to animal via injections) is required. Copper and cobalt are required for animal health because plants do not take these up- they don’t need them to grow – so soil applications don’t help.

Importantly, iodine may be needed because brassicas produce giotrogens which affect the thyroid so iodine supplementation is potentially used. Again, not really plant available so a mineral lick is a cheap and easy option to avoid any potential issues.

In most cases the management of brassicas to avoid these problems is well known- it is well covered in Lincoln University’s animal science papers – but the practice of grazing brassicas on-farm has fallen down because a farmer is short of feed, weather has been overcast or low stock numbers are allowing too high an intake.

We have also had reports of scald from animals grazing lucerne in dull conditions in early spring when the lucerne has high N levels and these aren’t converted to proteins quickly enough. The easiest management is to remove animals from the crop for a few days for it to mature – and introduce them slowly to the crop at about 20% of diet for the first few days- basically restricting access and allowing time on a different feed source dilutes the compounds ingested on the rape/lucerne or other high N containing forage. This reduces the likelihood of an animal health issue developing - all things people know but tend to forget when under pressure.

 

Can I reduce bloat in a cattle grazing system if lucerne was mown and left to wilt before it was grazed?

Yes – the issues around bloat can be dealt with in several ways. Ultimately, we never know when bloat is going to occur so we need to think about how to reduce the risk and have a range of strategies that we can put in place during periods when the risk of bloat increases.

Bloat seems to be more of an issue with young fresh lucerne that experiences a change in weather conditions, for example a cold day after several hot ones (or vice versa) or rain after heat leading to a rapid flush of young growth. This makes it difficult to research and so we try to minimise the risk. The strategies we can use include:

  • Ensure animals are not hungry when going on new lucerne – this may actually mean move them on a half day earlier than you though necessary so they are not empty. Grazing animals tend to stop eating knowing they will be getting a fresh break later so why bother eating low quality stalky feed? This means that there can be a mini empty period that we don’t realise and by moving them earlier you avoid it.
  • Bloat capsules for cattle that are older than about 15 months of age.
  • Bloat oils in water troughs.
  • Access to salt (sodium Na) – mineral blocks available at all times.
  • Mixed grazing of sheep and young cattle i.e. the sheep are more likely to grab the lush top leaves than the cattle.
  • Access to fibre – any sort of hay - but you may find only some animals will eat it.
  • Access to a neighbouring paddock or area with grass - preferred ruminant diet is 70:30 legume:grass.
  • Wilting the lucerne before grazing- this will reduce the water content and by definition increase the fibre percentage – a few hours is all that would be necessary.

You may not need to do all of these things and some people do none of them but even our most experienced farmers can occasionally get bloat. These are the strategies available to reduce the risk. Implement one or more of these strategies when there are sudden changes in weather conditions that could cause a change in the plant which increases the potential risk of bloat in your grazing stock.

 

 

 
Why am I getting so many bearings occurring in my hogget flock carrying singles which are set stocked on lucerne? 

 

Note: In this case lucerne was set stocked with single bearing hoggets prior to lambing. Estimated 20-30% of the hoggets were bearings, with about 5% suffering prolapse in the 12-48 hrs after lambing.

Doug Avery replies: 
“Bearings were once a huge problem at ‘Bonavaree’, but while we still get the odd one it is no longer seen as a significant problem. In recent years Fraser has managed feeding from scanning to lambing very closely, every day ensuring only the right amount of feed is issued to each sheep class. We would never lamb single lambing sheep on lucerne. We only lamb multiple birthing sheep on high power feed. Our single ewes and hoggets are held on very tight rations right through pregnancy and then fed better once the lambs are out.

Response from the LU dryland team: 
We took a look at the published literature to see if we could get a bit more info on what might have happened in this case. Unfortunately, no one factor has been identified as the cause of prolapse and some reports are contradictory. The UK based NADIS (National Animal Disease Information Site) website gives great descriptions of the condition and outlines some of the factors implicated in the cause of vaginal and uterine prolapse. Beef + Lamb New Zealand R&D Brief 120 (Coping with bearings) also provides useful information.

 

Without further information our best guess would be the hogget flock set stocked on lucerne carried excessive body condition at lambing and large single lambs were produced. The NADIS site mentions prolapse at birth can be associated with prolonged 2nd stage labour resulting in the birth of a large single lamb. Bearings occurring in next the 48 hours after lambing were associated with those animals which required intervention during lambing and continued straining after birth in response to pain and swelling in the reproductive tract.

 

Excessive body condition has been mentioned as a possible factor leading to bearings. However, other research could not replicate the increase in bearings in a ewe flock due to increased feed supply but they mentioned gorging did not occur even though many stock has CS>3 at lambing (Litherland et al., 2000). Their work did show 20% of ewes which had bearings in the previous year prolapsed in the next pregnancy. Their recommendation was to identify and cull bearings.

 

Some reports also mention potential heritability of vaginal prolapse and recommend also culling progeny of bearing stock. The recommendation in this case would need to take account of whether grazing management lead to excessive hogget weights and large lambs to animals in their first pregnancy was the main factor influencing the number of bearings in the hogget flock on lucerne. Regardless, the hoggets which prolapsed need to be culled and their progeny identified. This way if trait proves heritable those progeny can be identified and culled to remove the trait from the breeding flock.

 

A range of factors have been implicated in the potential for stock to suffer prolapse. These include diet quality, exercise, short docked tails and other factors. It appears further research is needed to explain the impacts of these factors on the potential for prolapse up to and beyond lambing.

 

References: Litherland, A.J.; Lambert, M.G.; Knight, T.W.; Cook, T. ; McDougal, D.B. 2000. Incidence of bearings in ewes that had a bearing at the preceding lambing. Proceedings of the New Zealand Society of Animal Production 60: 44-46. NADIS website: http://www.nadis.org.uk/ Beef + Lamb New Zealand website: http://www.beeflambnz.com/

 


Why are my stock not performing as well as expected now they are grazing lucerne?

There can be several reasons for poor LWt gains in stock direct grazing lucerne. They can all be dealt with but it important to accurately identify why performance is poor so the appropriate action can be taken.

  1. Ensure they have had a B12 injection – “Ill thrift” can occur if Cobalt levels are low and this can occur in regions when it hasn’t before because lambs are eating the top of the plant not the bottom near the soil surface. In most regions of New Zealand cobalt requirements are usually meet when stock ingest soil while grazing. B12 is essential for all lucerne grown on volcanic soils which are naturally low in cobalt. This has also been an issue on ex-forestry land in Canterbury.
  2. Dull weather can lead to high protein levels in lucerne but not really a nitrate issue. The high protein diet can’t be effectively utilised to grow the animal. Ensure fibre is made available (supplement with hay).
  3. Excessive N can actually lead to photosensitivity in ears and nose because green pigments can remain in the blood stream. This usually causes only cosmetic issues. A period off lucerne is the most important here and sunshine usually cures it.
  4. The high protein can also mean the lucerne lacks sufficient energy in the diet – feeding grass or grain with the lucerne can balance the diet.
  5. If it has been wet in summer the lucerne can get lush again, just like in spring, and rapid passage through the animals occurs so fibre should be offered.
  6. Parasites are usually less of an issue on lucerne than grass but on wet herbage or areas where there may be a hot spot e.g. lambs can be vulnerable in a stock camp that ewes shed on in a previous rotation.
  7. Another reason may be a lack of time grazing to allow for the rumen to adapt to a change in the quality of the feed (i.e. moving from grass to lucerne). This is more likely to happen on properties which have minimal lucerne and are unable to create the optimal 6-paddock rotational grazing system.
  8. Empty gut syndrome: trying to get the stock to eat the last stemmy parts of a lucerne plant can actually leave animals “empty” for 1-2 days before shifting.

 

Can I use my lucerne for ewe mating?

As always it depends; there are several farmers routinely mating all of their stock (ewes and hoggets) on lucerne and others report depressed scanning and lambing rates after doing so. It is important to understand why the answer is yes and no.

Lucerne that is fresh, young, leafy and free of insects (aphids) or foliar diseases has been used successfully to flush on. Equally in the grips of a major drought with only dry grass, wilting lucerne has been used with success. Stock that are not used to lucerne may experience a period of ruminant adjustment (similar to being moved onto a brassica) so consider this in the flushing period. Hopefully ewes coming off grazing lucerne have higher body condition which usually translates into higher scanning and lambing percentages.

Don’t use lucerne that is in full flower. At this advanced stage of maturity lucerne reportedly has high levels of coumestrans which can suppress ovulation rates. This creates a dilemma because autumn is the period when we want lucerne to flower to recharge underground reserves – so some planning in needed. If you have alternative feed available flush on that and put ram lambs or cattle. If not, use the freshest youngest lucerne during mating and allow stands to flower either well before (January/February) or allow a long period of growth after mating. If aphid levels are building up in autumn spray them prior to flushing.

Any negative effects on ewes are usually gone after three to four weeks of grazing other pastures and are not permanent. For more details on experiments check out our blog post or this report (300 KB).


Can I graze dairy calves on my lucerne?

Note: this relates to 130 kg calves where the farmer was unable to use bloat capsules as the animals were below the 150 kg liveweight required for capsule use.

Give the calves about a three to four day break. Ensure they have easy access to a fibre source and salt and don’t put them into a break hungry. Irrigated lucerne, or after you’ve have a rain event, that is young and lush will be the most difficult time. Bloat is difficult to predict but sudden changes in weather (for example cool after hot or hot after cool) have both been mentioned anecdotally to cause the issue. In contrast, in dryland stands, by mid-summer the lucerne has usually dried off sufficiently that animal health issues are rare - until we get a rainfall event. I will never say you won’t get bloat but you should be able to avoid it particularly as we go later into autumn – except after a drought. Some dairy farmers use bloat oils in drinking water for clover rich pastures. Visit our blog for more information and for other advice that may be helpful.

 

How risky is it to solely graze lucerne with yearlings through late spring and into summer?

It has been done successfully in many places - if you have concerns a bolus at 15 months is an option - but late summer the feed has usually hardened up (less lush, more fibre on offer) to the point where bloat isn’t an issue.

A couple of points to be aware of are the need to take care if grazing following a drought breaking rain when lush rapid growth occurs. Always make sure you have salt and fibre available – especially when the feed is lush and even when they don’t seem to be eating it.

Also ensure you move animals on a half day before you think they need it – that way they will never go on a new break hungry - but if you force animals to eat every last leaf some will actually not have eaten for 24 hours knowing the new break is coming and then gorge themselves and bloat can be an issue.

 

Can I use lucerne to feed my dairy cows?

Much of South America grazes dairy cows with lucerne and lucerne grass mixes. There are several farmers in Canterbury who use it as part of their rotation – it is used both as a supplement – with some cropping farmers now growing lucerne for dairy and reducing their arable cropping. Lucerne makes an ideal protein rich supplement and is frequently used in total mixed rations in the United States and here in New Zealand.

Direct feeding of lucerne is also practiced provided you follow some rules – make sure animals have access to salt and fibre and for cows – Ensure the bloat issue is dealt with- either with capsules or oils. This is common practice for those who have clover rich pastures. 
For those who have irrigation but insufficient water to fully irrigate lucerne provides an ideal buffer –it can be irrigated less than ryegrass. There have also been several studies done at Taranaki dairy centre and a couple by DairyNZ – that have shown mixed results but usually lucerne is as productive as grass based pasture in spring but higher in summer.

A simple way to start using lucerne in a dairy system would be to use the first spring regrowth, which is always the heaviest, to cut and carry for supplement. This would make sense for those systems that develop a grass surplus in spring and allow greater control of that grass surplus and reduce seed head production. From then on graze the lucerne as part of the rotation. In dry years it will harden off and the risk of lush lucerne causing bloat etc is not a problem. In wet years- you should have sufficient feed anyway from the grass pastures so use the lucerne as a supplement.

And finally if you are putting in pastures - you can add lucerne –it won’t like being rotationally grazed at 3 week intervals but in our experience it may still be better than white clover that losses its tap root after 18 months and therefore fails to thrive from then on. Grazing lucerne when it is 30-35 cm tall would be ideal so if you only have one or two paddocks – you may be able to drop them out of a rotation for a round and then feed them off. Lucerne as part of a grass based mixture is an option dairy farmers should consider when renewing pastures, particularly in areas where summer dry periods can occur.

There is a lot of straight agronomic advice on our website to get started - being unsure of the soils etc. We cannot guarantee success – but if you have one paddock going well – we would suggest more!

 

 

 

Conserved Feed

Is there a difference in N levels in good meadow hay with high clover content compared with lucerne hay?

Not really – however, some meadow hay can cause problems because endophyte levels in the grass can be high which can cause animal health issues. This will depend on the type of grass and when it was cut. There should not be any issues if the hay was taken from non-endophyte based grass pasture, for example timothy based pasture.

 

What crude protein levels should we expect from baled lucerne hay to supplement cattle grazing?

The crude protein level in lucerne hay is dependent on the DM yield at cutting.

The protein level of lucerne leaf is consistently around 28% compared with stem which consistently has around 11% - so then it is a straight dilution. If the lucerne stand was cut at a yield of 5 t DM/ha, when it had 50% leaf and 50% stem, the average protein would be 20.5%.

In any lucerne stand about 2.5 t DM/ha is high quality leaf. The result is lower quality stem material. So if you have a 5 t DM/ha yield then the 50:50 rule would apply and the protein would be about 20.5%. If it was a 7 t/ha crop when harvested then about 35% was leaf and about 65% was stem so the crude protein would be about 18%. So a greater quantity of feed was conserved but the quality is lower.

But - that is purely on a yield harvested basis. What the cows eat will depend on how well you feed it out. If the hay is too dry and all the leaf falls off you are feeding them lower quality stem. Given the chance they will eat the leaf. To make things work you could make silage at about 5.0 t DM/ha using an inoculant. With the wetter silage the leaf tends to stay attached more than with hay. But if you do chose to make lucerne hay – ensure you keep as much leaf as possible.

 

Does lucerne hay, when used as horse feed, contain high levels of nitrogen when fed out? 

No - lucerne hay is the preferred source of feed for horses all over the world since Genghis Khan took it with him to conquer Asia. In the horse racing industry it may be used in the form of pellets, hay or baleage.

 

Is the nitrogen concentration the same or different in lucerne baleage compared with lucerne hay?

The difference relates to at what growth stage the lucerne was at when harvested. If it was young fresh and leafy with no flowers it will contain a higher nitrogen percentage than mature lucerne which was conserved at flowering.

 

Is it correct standard tests can underestimate ME in lucerne baleage?

At Lincoln we have not come across this issue. In theory it could possibly occur if the machine being used to analyse quality of the baleage sample has not been calibrated specifically to lucerne and is working off a grass based calibration. However, a well calibrated lab service should be able to give accurate measurements of lucerne ME. Ask if their machine is calibrated for lucerne.

Silage and baleage both require high levels of sugar to grow Lactobacilli bacteria that cause the ensilage process to happen. Because lucerne has high protein levels it can have low water soluble carbohydrate levels (sugars) which is why an additional source of sugar or inoculant is recommended when making silage.

 

Is there a risk to feeding lucerne baleage to cycling breeding cows when the bull is out?

Baleage is fine for supplementary feed unless:

  • It was in full flower when cut
  • It was attacked by aphids &/or had leaf diseases when cut.

Both factors can result in increased levels of a phyto-oestrogen compound called coumestrol. Previous research indicates these compounds remain in the feed when made into baleage or silage (i.e. they don’t degrade after the lucerne is conserved). Levels stay elevated so don’t use for flushing feed (but it’s ok for non-breeding stock). However, fresh vegetative lucerne (without pest or disease) eaten in situ or made into baleage is fine. Check out our blog post.

 

How can I use lucerne to produce high quality silage?

The main issue for lucerne silage is that it has high protein content, but the ensilage process requires high sugar levels. There are two ways to overcome this:

  • Use a commercially available silage inoculant, or
  • Add a source of sugar (e.g. Italian ryegrass) layered throughout the lucerne.

If you try to make lucerne silage without adding an inoculant or alternative source of sugar, the ensilage process can be slow and non-desirable bacteria (clostridium) can multiply. These bacteria are less effective for making silage because they produce a weaker acid. When you have high water soluble carbohydrates (like sugar that dissolves in your tea), then the bacteria responsible for making silage (Lactobacilli) thrive. This is why young leafy grass is good for silage. But you can help the lucerne by adding sugar by including a leafy grass, perennial, or preferably a tetraploid or Italian ryegrass, etc.

By layering the ryegrass and lucerne you evenly distribute the sugar source (ryegrass) throughout the silage.

The addition of other high protein species (e.g. red clover) to lucerne will not help the ensilage process because it has the same issue – high protein content. Herbs, such as chicory or plantain, will also not be as effective in increasing silage quality compared to an Italian ryegrass because they have a lower amount of water soluble carbohydrates.

 

Is lucerne quality affected by the date of shutting up for silage?

No - the quality of conserved is based on the ratio of stem to leaf and that is pretty consistent throughout the year.

Cutting a 5 t/ha crop for silage in October will have the same quality as a 5 t/ha crop cut for silage in December (unless the December one is dryland and may be shorter and flower earlier so then the quality could be a bit lower). This is because your lucerne crop will never have more than ~2.5 t/ha of leaf. So for these crops you have 2.5 t/ha of leaf and 2.5 t/ha of stem so the silage ends up similar quality. If you cut at 4 t DM/ha you’ll have 2.5 t/ha of high quality leaf and 1.5 t/ha of stem – so higher quality overall.

If you close your lucerne stand early but keep the same harvest date you end up with more silage of lower quality. For example if you produce 7 t DM/ha again only 2.5 t/ha is leaf the other 4.5 t/ha is lower quality stem material which dilutes the high quality leaf material. This is not recommended as you need to balance quality and quantity of your conserved feed. On average the 2.5 t/ha has an ME of 12 MJ/kg DM and a crude protein of around 28%. The poorer quality residual has an ME of 8.0 MJ/kg DM and crude protein of 11%. So a weighted average will give you an idea of the quality of your silage.

 

Nitrogen Fixation

Can all pasture legumes fix nitrogen?

Generally, yes. But it is actually the rhizobia bacteria which inhabit nodules on the legume roots which fix the nitrogen (N). The plant swaps carbohydrate (formed during photosynthesis) for fixed N from the bacteria in a mutually beneficial symbiotic relationship where both partners benefit from the relationship. However, some legumes require specific bacteria strains to fix N for them (e.g. lucerne, Caucasian clover, Lotus corniculatus) and this is why it is important to inoculate legume seeds before sowing especially if there is no recent history of that legume in that paddock. Other rhizobia present in the soil can also infect the nodules but if they aren’t the ones needed they form small ineffective nodules – that is they become a carbon drain on the plant. The plant continues to supply the bacteria in the nodule with carbohydrates but it doesn’t receive any fixed N in return. Effective nodules are pink inside if you cut them in half.

 

How much nitrogen can pasture legumes fix?

In general both annual and perennial clovers fix nitrogen (N) in direct proportion to the amount of dry matter (DM) they produce. You can expect to get at least 25 kg N to be fixed per ton of clover DM grown. So if a 10 t DM/ha/year pasture has an average of 20% clover content in the DM, the 2 t/ha of clover produced would contribute 50 kg N/ha of pasture annually. This is, of course, insufficient for maximum grass growth and dark green urine patches will be an obvious indication that most of the grass in the pasture is N deficient.

We have detected little difference between species in N fixing ability. A comparison between irrigated white and Caucasian perennial clovers growing in ryegrass pastures showed that both fixed about 26 kg N/t clover DM produced (Widdup et al. 2001). In dryland pastures we have shown that sub or white clover sown with cocksfoot fixed about 28 kg N/t of clover produced (Lucas et al. 2010). Other studies on volunteer clovers such as haresfoot and striated clovers have revealed similar rates of N fixation per ton of clover herbage produced. Australian work (Peoples & Baldock 2001) on N fixation by a wide range of herbage legume species, including clovers, has also conformed to this general rule.

The 25 kg N/t legume DM grown is a conservative estimate. It takes no account of the N content of roots and nodules (because basically it’s difficult and time consuming to routinely dig up all the roots and nodules). Work where roots and nodules have been measured and included in N fixation estimates indicate that total N fixed is over 40 kg N fixed/t of legume DM.

 

What factors limit N fixation?

Anything that reduces legume production will reduce the amount of N fixed!!

Nutrient availability, soil acidity, seasonal temperatures and the development of water stress can all compromise the ability of legumes to grow and thus the amount of N which can be fixed. BUT: the main limitation is caused by competition from companion grasses in pasture mixes.

Legume production, and with it, N fixation are limited by nutrient deficiencies such as phosphorus (P), sulphur (S), molybdenum (Mo) and boron (B). Low soil pH, especially soil pH (in H20) <5.5 , causes an increase in soluble aluminium levels which can be toxic to some legumes and inhibit the ability of the plant to explorer deeper soil layers for water and nutrients. Acid soils can also impact on the ability of some N fixing rhizobia to survive.

Cool winter temperatures restrict perennial legume production more than annual clovers which are adapted to grow rapidly in late winter early spring before the onset of summer drought.

Soil moisture deficits will also limit legume productivity because as the soil dries less water is available. This also restricts uptake of nutrients from the soil, which enter the plant in solution, via the roots.

However, the main limitation to legume production and the associated N fixation is competition from grasses. A pure stand of white clover in a summer rainfall area or under irrigation will produce at least 10 t DM/ha/yr and fix 250 kg N/ha/yr. Red clover and lucerne can produce much more DM and N than that. Annual clovers grown as a pure stand in a deep soil in a summer dry, 750 mm rainfall climate will also produce at least 10 t DM/ha/yr and inject 250 kg N/ha into farm system. Under ideal conditions some annual clovers will produce 14 to 16 t/ha DM. This can therefore be equivalent to about 400 kg N/ha.

Where legumes are grown alone and grazed in situ (e.g. lucerne) the N fixation rate per ton legume DM grown may decline over a period of several years. This is because soil N accumulates in the absence of a grass to exploit the high soil N. It may therefore, eventually be more efficient for the legume plant to take up soil N rather than use carbohydrates from its current photosynthesis to fix more N. Ultimately, legumes are lazy – there is a lower energy cost to the plant if it uses “free” soil N rather than paying for N fixation by supplying rhizobia bacteria in the root nodules with carbohydrate.

As soil N accumulates under legume dominant stands grass weeds tend to invade. Management options then include grass killing herbicides, hay or silage crops to deplete soil N, over drilling desirable grasses or exploiting the accumulated soil N by replacing the legume with a non-legume forage or cash crop.

 

What are some of the factors which can affect nodulation of legumes?

There are a few things that can affect nodulation

a) White clover is usually fine for nodulation on resident bacteria in the soil and people are no longer inoculating every time they sow white clover. However, some of the resident bacteria can be less effective (they fix less N for the plant but cost the plant the same amount of energy) than the introduced ones in commercial inoculants. Also some nodule invaders may actually not be rhizobia and are parasitic – they have the gene to tell the plant they are fixing N but actually aren’t fixing any - cunning bacteria! There is work in progress at Lincoln on this at the moment.

White nodules on white clover may be:

  • Ineffective and not rhizobia
  • Effective but not currently active.

 

b) Lucerne - usually needs to be inoculated unless it has been sown into a paddock that had lucerne within the previous 4-5 years and an ongoing high pH (>5.8 in H2O). However, even when inoculated not all of the bacteria that occupy the nodules will be from the inoculant – some will be resident bacteria from the soil and may be less efficient at N fixation – we actually don’t know what bacteria populates the nodules over time especially because lucerne periodically sloughs off the nodules during periods of low N demand (winter, water stress, high soil N conditions).

On lucerne the nodules are more like long sausages in clumps – and sometimes pink (see photo below) and sometimes white- they are difficult beasts to work on for that reason.

 

Healthy nodules formed on a lucerne plant sown at Lincoln University. 

 

c) Longevity of rhizobia - at this stage we suspect the soil around white clover may only contain the inoculant for a few months. For lucerne it may be in proximity for several years. After that it is a jungle of soil bacteria and no-one really knows the dynamics hence we have some work happening regarding this issue at the moment.

d) Lack of pink nodules – rhizobia are not always active and fixing N for the plant- they will be pink and operating when the plant is actively growing but may be sloughed off when the plant is not actively growing. This occurs because the plant is in charge of the relationship and it is lazy. There is a cost to the plant of fixing N (N supplied in return for carbohydrate formed by the plant) so if they don’t need N because:

  • They are not growing much or
  • There is adequate soil N or
  • They won’t be fixing much N (although when they switch off we really don’t know – it differs between species.

e) At establishment lucerne may go all of the first year without fixing N because there is adequate soil N (from mineralisation after the soil is cultivated) to keep it going so it will form the bumps and take the rhizobia in but not actually start fixing until year two.

f) Clover root weevil (Sitona lepidus) – check for notching on the leaves – also attacks lucerne and can take 2-3 years to be controlled by its parasitoid. The weevil causes more damage on white and red clovers than on sub clover and lucerne.

 

Why are there no nodules on the roots of my lucerne plants in winter?

The relationship between rhizobia and lucerne is largely driven by the lucerne. In the middle of winter when the plant is not growing it may not have nodules on it. The plant has a low demand for nitrogen at this time so it may have sloughed off the nodules. This is not a problem and there is no need to panic.

We believe the lucerne preferentially uses soil available nitrogen before fixed nitrogen. When spring kicks into gear lucerne can become yellow and this may be due to any number of issues such as a sulphur deficiency or a lack of nodulation. The symbiosis (the forming of the relationship between the rhizobia and the lucerne plant) takes time to re-establish each spring and because the lucerne is responding to air temperatures and the root to soil temperatures there may be a mismatch in nitrogen demand. However, the lucerne then gets fixation going and usually fixes about 28 kg N/t DM grown.

The rhizobia in the soil that have sloughed off can multiply and repopulate nodules relatively quickly. In the absence of any lucerne for a five year period their can still be sufficient rhizobia in the soil to nodulate a stand- provided the soil pH has remained sufficiently high (around 5.8 in H2O in NZ or 5.2 in CaCl if you’re in Australia) for them to survive.

In our experience, knowing exactly when you will find nodules has been difficult – but their absence is not always a bad sign - it is quite common. The only time to panic is if you are going into a site that has low pH (<5.5 in H2O or about 4.4 in Australia), no history of lucerne and you forget to add the rhizobia. Even then it can be recovered by applying a slurry in the evening before rain to inoculate the soil. So in winter n absence of nodules is expected.


I have just sown my lucerne but there is no sign of nodulation. What should I do?

In an establishing/1st year crop the availability of soil N from mineralisation following cultivation often means lucerne will not form nodules for at least a year – until it runs out of “free” soil N. White pimples on the roots could then be the root hairs saying hello to the bacteria and capturing it but not actually switching on the N fixation because they don’t need to yet. Then when soil N is low they may “turn on” and then grow and become pink. The process is actually controlled by the lucerne - not the rhizobia bacteria.

The healthy paddock may also have small nodules if there is adequate soil N. So don’t judge a lucerne paddock by its nodules - it will always disappoint you! The thing is it can have a few clusters of nodules that are fixing lots of N really efficiently or one nodule doing exactly the same! What you don’t usually find is masses of nodules all over lucerne roots, which is common in clover species.

 

Why are there no nodules on my 2-year-old lucerne stand in mid-October?

At this time of year a lot of lucerne does not have nodules on it if the soil N levels are high – but in a second year crop it may not have nodulated at all last year depending on yield. At Lincoln we have had an inoculated crop grow as much as an inoculated one for the first year based on soil N levels but observed a yield loss in the inoculated stand in Year 2. Ideally, sow fresh peat slurry inoculated seed or commercially available coated seed. If the stand was not inoculated at sowing spray a slurry of peat inoculant over the paddock in the evening when there is about 15 cm of herbage – no more - The rhizobia bacteria will be killed by exposure to UV light (and a range of other factors like storing inoculated seed in areas with high temperature etc.) so you need ground cover to prevent the sunshine killing the bacteria. Applications just before irrigation or rain is best to wash it into the soil.


It’s autumn and we have a mid-age lucerne stand (4-5 years-old). It looks healthy on top but underneath the nodules are white and very, very small and another paddock that is extremely healthy but the clover is looking yellow around the edges. Is there anything wrong and what should we do?

Everything sounds normal for this time of year. Lucerne is a lazy plant and fixing nitrogen has a carbohydrate cost. This means if there is high soil N – which may come from the urine returns from direct grazing in a mid-age stand – lucerne will preferentially use the freely available N in the soil and N fixation is likely to be reduced. This means there will be fewer nodules.

The small white pimple-like nodules could be either

  • Ineffective nodules formed by bacteria other than rhizobia trying to claim carbohydrate from the lucerne but which don’t supply N to the plant in return OR
  • Rhizobia that are not currently fixing N because there is low plant demand for N or it is being met by soil N.

If the paddock is poor performing the lack of N could be due to

  • The soil pH is too low and Molybdenum is an issue OR 
  • It is a paddock that didn’t nodulate well at establishment.

 

Forages

What is the dry matter content of autumn sown ‘Moata’/Italian ryegrass and does it vary between irrigated and unirrigated pastures?

Short answer: DM% can’t reliably be estimated so you will need to measure it. Unirrigated, stressed pastures/crops are highly likely to have a significantly higher DM% than the irrigated.

Longer explanation: Dry matter percentage varies throughout the year (and throughout the day) so the only accurate method is to measure it directly.

In round figures an irrigated actively growing Italian ryegrass pasture in summer could be 10% DM. In contrast, in winter an Italian ryegrass pastures could be 20% DM. This is a 100% difference in your total yield estimates from the same mass of fresh herbage. Because of this farmers frequently overestimate their Italian ryegrass yields and under feed stock at certain times of the year.

In summer/autumn the irrigated pasture is likely to have a lower DM% than the unirrigated crop. Depending on the level of water stress that could be 10% DM in the irrigated pastures versus 15% DM in the water stressed pasture. This would translate to 50% yield difference in yield estimates made from the same mass of fresh herbage.

Irrigated plants produce leaves with large plant cells and expand these to maximize light interception (larger cells = larger leaves = more light interception = more energy and area to photosynthesize and produce more dry matter). When nitrogen deficiency, or temperature or water stress, kicks in then leaf extension/expansion is usually the first thing to be affected. These stressed crops look shorter and individual leaves are smaller. However, the large leaves on irrigated plants are full of water and their vacuoles (storage organs) are empty. In contrast, on dryland or winter sown pastures, where leaf extension is restricted, leaves may be shorter but photosynthesis is proportionately less affected. This means the plant makes sugar but has less leaf area to allocate it to. The stressed plants then store the sugar in those vacuoles as starch. 
Dry matter is essentially a measure of the amount of that sugar that is stored per until leaf area. So our highest quality pastures, those with high sugar levels, are usually those grown over winter months. They are short and leafy with a high sugar (DM) content.

Equally, standing pasture at the early stages of a drought will also be high quality because the leaf expansion will be reduced proportionately more than photosynthesis. So again there is a build-up of sugar in the leaves and the ME is often higher than initially thought – until it starts to die but that’s a different question. So one bite of a pasture for a lamb/cow or deer is not the same as another one – it depends on the DM content of the feed. Low leaves often require more bites to achieve the same level of DM intake.

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