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Lucerne Masterclass

The Accelerating Change Lucerne Masterclass drew a large crowd of dairy farmers, contractors and service providers to Scott Fitzgerald’s farm in Tongala last week. We saw some sunshine after a few days of heavy rain, making it the perfect opportunity to get into the paddock to have a look at how the lucerne was performing both above ground and how the crop was performing beneath the surface, with some soil pits.

Many farmers in the Murray Dairy region have been using lucerne or are thinking about using it as a perennial, summer-active feed. Lucerne is often used on dairy farms to fill feed gaps in late spring or late autumn and provides a good source of protein throughout warmer months. It has a higher tolerance to water stress and higher irrigated water productivity than perennial ryegrass pastures which makes it an attractive feed source for those managing uncertainty in the water market and climate. However, for optimal quality, yield and persistence lucerne must be managed well.

Luke Nagle, Agronomist from Advanced Ag, and Scott kicked the day off, describing the value lucerne brings to the Fitzgerald’s feedbase, and what separates a good lucerne stand from a great one. The overwhelming take home message from Luke and Scott was that PREPARATION IS KEY for stand longevity and performance of lucerne. Getting everything right before lucerne goes in the ground, from soil preparation, to weed control, varietal selection and timing, is critical to not only establishing a great stand but also the highest possible return on investment. This message was reiterated by presenter Frank McRae, Chair of the Australian Fodder Industry Associated (AFIA) and Product Development Manager for AusWest Seeds, and Soil Scientist, Christian Bannan, who also presented to the group.

PLANNING AND PREPARATION IS KEY

A critical first step of preparation is selecting the right paddocks that are appropriate for your purpose. Scott discussed the importance of irrigation layout, soil type and drainage when selecting his lucerne paddocks. Lucerne is intolerant of wet soil and poor drainage during establishment. Selecting the right bays on his farm with more freely draining soils and optimal surface drainage has improved lucerne establishment and yield at the Fitzgerald’s compared to longer and more uneven bays sown previously. If lucerne is to be used as a grazed summer feed, paddocks should be within close proximity to the dairy. Grazing of lucerne must be carefully managed to avoid damaging and degrading the stand and may require that you take cows on and off the lucerne within a short time frame, particular when it’s wet. Minimising the walking distance for the herd will allow you to be more flexible and responsive to how it is grazed. When considering how much area to sow, try to aim for rumen consistency by sowing enough lucerne to get a grazing every day through summer, approximately a 25 day rotation. Cutting lucerne gives you some more leeway on location, but no matter how you use it, it’s critical that bays are well drained.

The Lucerne Masterclass also covered the importance of preparation below the surface. This was made evident by looking at the root development of two different lucerne plants that Luke had brought along – one that had been sown into a ripped bay and established a strong root system as a result, and another where root development was impeded by a hard pan below the top soil. A hard pan layer is commonly found throughout our region, especially in duplex soils under flood irrigated, grass-based systems (we’ll get to the details and management later). Plant development on the surface is a direct reflection of the root development underneath. When considering which paddocks to sow to lucerne, make sure you diagnose any subsurface constraints below the surface and determine if they can be ameliorated. By the time you see a production impact as a result of sub soil constraints, the options for remediation are often limited or not practical or economical to correct.

Luke Nagle demonstrates how lucerne root development can be impacted by soil condition

Preparation for lucerne is not just a matter of tillage and fertiliser application prior to sowing, it requires careful thought about crop rotations, weed management and paddock selection in the preceding seasons. Once a crop is in the ground, you have limited opportunity to remediate soil constraints or manage broad leaf weeds. Frank and Luke both highlighted that you can get at least five years production from some lucerne varieties under good management and with the right seasonal conditions, but attention to detail in preparation is key to getting this result.

Think long term when assessing how lucerne fits into your feedbase. Paddock rotations can help to control weeds such as couch grass, white clover, wireweed and capeweed which are most commonly a problem in lucerne. Converting from old perennial pastures into a new species such as lucerne can bring up a multitude of weed issues. Pastures should be sprayed out well in advance and ideally substituted with a cereal in autumn (if spring sowing), to allow for broadleaf weeds to be controlled before lucerne is established. This will not only provide an opportunity to clean and prepare paddocks in advance, but help to open the soil for lucerne root development.

REMEMBER: It is extremely difficult to control grass weeds in a grass pasture or crop, and broadleaf weeds in a broadleaf pasture or crop. Identify what persistent weeds you have and what type of rotation may give you more options to address them.

Frank discussed with the group the importance of considering what you grow post lucerne as well as in preparation in your rotation. It is not recommended to follow lucerne with another lucerne stand, as it significantly increases the risk of disease, weed and pest issues. As a deep-rooted legume, lucerne also helps to open the soil and to fix nitrogen, so it works well to follow it with maize or a cereal, to take advantage of good soil fertility and structure.

AUTUMN VS. SPRING SOWING – IT’S UP TO YOU (AND THE WEATHER)

The short of it is, there’s no real rule about when to sow. Some participants at the Lucerne Masterclass said they sow in spring, others in autumn. Scott had done both. It depends on the weather, your preparation, and the risk you’re willing to take.

Lucerne is a summer active species, so does not like boggy or cold soil. Strike rate can be compromised in wet autumn conditions. If you are sowing in autumn, go in no later than March and irrigate up or after some rain (usually mid to late April) for rainfall germination. The later it gets, the lower the soil temperature and the higher the risk to the seed. The benefits of sowing in autumn are you can take advantage of rainfall for cost effective establishment, and you will have an established stand to graze by the coming summer.

Sowing in spring is recommended if you need time to prepare over winter, for example by growing a cereal break crop, or if you are concerned about wet weather in autumn. In spring you can take advantage of higher soil temperatures, and if there is low spring and summer rainfall, control moisture applied whilst the plant is particularly vulnerable to waterlogging during establishment.

LUCERNE IS SENSITIVE TO GRAZING

Lucerne doesn’t like to be trampled, sat on or intensively grazed (too bad that’s what cows like to do!). As a result, cows should only stay on lucerne for a few hours to protect the longevity of the stand. Scott brings his cows back to the dairy after a morning feed for a top up and some time under the sprinklers. Cows can be picky so pre-mowing and topping lucerne can help prevent cows from selectively picking off leaves down the stalk, rather than eating it down evenly. This is particularly true with stalkier varieties, which also tend to be the higher dormancy ones (explained below). Of course, this adds labour time and machinery costs, so ongoing assessment out of grazing pressure as the herd goes in and out is important to understand if your stand will benefit from a top. Look out for stalks that have been stripped of leaf or whether stalks have been eaten down.

TOO MUCH WATER IS MORE DAMAGING THAN TOO LITTLE

Accelerating Change Project Officer, Harriet Bawden, and AgVic Research Agronomist, Kevin Kelly, highlighted the research that had been conducted in the region looking at the impact of different irrigation strategies on lucerne. Lucerne provides a good alternative to other perennials, such as ryegrass, where water availability and price is a concern.

Research shows that the production of lucerne is linearly related to water use (to point of meeting plant water requirements). This is consistent with the findings of the Accelerating Change monitoring and measurement strategy, which looked at the impact of different irrigation intervals on one of the project’s Partner Farms.

Irrigation management of lucerne can be more flexible than the irrigation management of some alternative forages. As shown by an experiment using different irrigation frequencies – 40mm, 80mm and 120mm – lucerne is able to survive in water limiting conditions, minimising water usage during stress and becoming semi dormant. It has a strong tap-root system which enables it to source water from depth. When we looked in the soil pits under Scott’s lucerne, roots were evident at 80-100cm, although they have also been known to extend deeper. Another experiment using different irrigation strategies – full irrigation, partial irrigation and dry off for 1, 2 and 3 years – demonstrated that irrigation water to lucerne can be “switched off” over irrigation seasons (within reason) and recover to full production. This highlights how flexible lucerne can be in an irrigated farming system, as short term irrigation strategies to reduce water use can be managed to prevent long term yield penalties or persistence of the stand.

When it comes to water, the thing to remember about lucerne is that it doesn’t like wet feet. This means that good drainage is required for optimal results. In research trials where lucerne received too much water or was impacted by rain events which resulted in water on the crop for a prolonged period of time, plant density was diminished. After the wet winter of 2016 Scott, like many other farmers in the region, was forced to re-sow the lucerne on his farm. Sow lucerne in well-drained paddocks and keep an eye on the rain radar as autumn approaches – it’s best to hold off irrigations at that time if it looks like rain is coming. If you are in doubt, hold out on the irrigation!

SELECT A VARIETY FOR YOUR SYSTEM

There are an increasing number of lucerne varieties becoming available on the Australian market, with some to hopefully arrive from the US in the coming years. Frank spoke of the ongoing research and development to improve disease resistance, nutritional quality (leaf to stem ratio and lignin quantity in stems) and persistence in lucerne. For more details, see here. Lucerne varieties should be selected for their traits (especially disease resistance) and the suitability for your farm system, purpose and growing conditions.

Although lucerne is most active in spring and summer, there are different dormancies available on the market, reflecting their growth habit during the colder periods. The more “dormant” the plant, the earlier growth will slow in autumn and the later it will pick up in spring. Dormancies are numbered 3 to 10, with 3 having the shortest growing season and 10 having the longest. Frank suggested that those with higher dormancy lucerne (“winter active”) may get 2-3 additional grazings or cuts for the season but fewer seasons out of the stand due to potential damage caused by intensive grazing.

Source: Seedforce Lucerne Guide

UNDERSTAND YOUR SOIL’S PHYSICAL PROPERTIES AS WELL AS ITS CHEMICAL ONES

Even if you do everything to the letter on the surface, if you have less than ideal sub soil conditions the performance of your lucerne will be compromised.

A big focus of the Lucerne Masterclass, led by Christian, was to improve the performance of lucerne stands, by giving it the most optimal soil conditions possible to thrive in. The best way to get a grasp of any soil constraints that may inhibit production is to dig a hole and have a look at what’s going on beneath the surface. Chemical soil tests will not be able to diagnose all sub soil constraints that might be present.

Looking underneath the soil allowed us to see the depth of the different soil horizons and look for the presence of plant roots and soil moisture, which are indicative of soil and crop performance. To assess soil structure and condition in a lucerne stand, look not only at the depth of the tap root, and how far it can push down to look for water, but also for the smaller network of roots that source most of the plant’s nutrients. The more access the plant gets to nutrients, the more efficient it can be with available water.

There was a noticeable difference in the depth of the roots between the paddock that was ripped prior to sowing and the paddock that was not. A hard pan layer was present in the non-ripped bay, a result of many years of saturation (flood irrigating) as well as the traffic of machinery and cattle.

Christian had identified that Scott had a dispersive soil, meaning that the soil has a tendency to disperse, crust and seal up, impeding the movement of water and roots. (For more information on dispersion, see pg.23-5 in the Accelerating Change Soils Report). Dispersive soils can cause water-logging which, as highlighted by Luke and Kevin earlier in the day, which is detrimental to the survival of lucerne. This was not evident from the soil chemistry tests, given that they reflected soils which are non-sodic. The industry tends to relate dispersive conditions with sodic soils, however this was proven incorrect on the Fitzgeralds soils, which are typical of Shepparton Fine Sandy Loam soils of this region. An absence of sodicity or a “sodic” condition does not mean you do not have dispersive soils. Dispersion can be remediated with gypsum, which can be applied prior to or at sowing to achieve some soil incorporation. A dispersion test is easy for anyone – it requires placing an aggregate of soil from the desired soil horizon in tank water for at least 6 hours. See here for instructions.

Correct diagnosis of your specific soil conditions is critical to ensure you can address the problem efficiently and cost effectively.

Soil profile in Scott's lucerne: the top line shows the depth of soil disturbance reaching only half way through the A horizon (second line), the third line shows the B Horizon, and the circle is root depth.

INCORPORATE ORGANIC MATTER TO IMPROVE SOIL STRUCTURE

When it comes to soils, dairy farmers in the region always want to know about tillage. Soil constraints should always be identified as a starting point, to ensure that tillage is the right course of action. The presence of any physical soil constraints, like a hard pan, at depth will help you decide if you are likely to get a production response from ripping, and to what depth you need to rip. Aim for a depth that will shatter the identified physical barrier, not just a certain depth for the sake of it. Ripping can help to shatter hostile soils and sub-soils but heavy soils (especially those that slake or disperse) will settle back down if the spaces or ‘rip’ that is created through tillage are not filled with organic matter or incorporated with necessary soil ameliorants such as gypsum and lime. Organic matter and ameliorants are critical for stabilising soil aggregates. Stabilising aggregates from dispersion or slaking allows plants to extend their roots throughout aggregated soil and enables the movement of water and air within the soil.

Soils with a high clay content can also be broken open through a natural wetting and drying process which does not often happen in irrigated systems which are kept wet. Increasing irrigation intervals or drying off bays completely will allow the soil to enact its drying cycle over summer. Similarly, it is important that organic matter is opportunistically incorporated back into the soil at this time, to prolong the benefits of the clay cracking open. Organic matter might include plant stubble or root mass from a previous crop, manure or straw. Dryland crops can be used between spring-sown forages or crops to enable the soil to dry out. As efficient dairy feedbase systems aim to harvest as much organic matter from the surface as possible, you may need to prioritise building organic matter back into the system by actively choosing a break crop that can contribute large amounts of dry matter into the system. This could be maize or a cereal that is taken to grain and the stubble incorporated back in.

Lucerne Masterclass participants were given an abundance of information about how to take their lucerne stands from good to great. Overwhelmingly, the expert speakers of the day kept coming back to consistent and persistent attention to detail, starting from site selection and preparation, through to ongoing irrigation and grazing management. In our variable climate, lucerne can be a challenging plant to get right, but it’s water use efficiency, flexibility, perennial nature and quality is increasing its staying power as a key component of dairy feedbases’ in the region.


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