From the Experts

Good lucerne needs good management

By Dairy News

The Accelerating Change Lucerne Masterclass drew a large crowd of dairy farmers, contractors and service providers to Scott Fitzgerald’s farm at Tongala in December.

After a few days of heavy rain, the sun was out, making it the perfect opportunity to get into the paddock to have a look at how the lucerne was performing above and beneath the surface.

Presenters included agronomist Luke Nagle, soil scientist Christian Bannan, Australian Fodder Industry Association chair and AusWest Seeds product development manager Frank McRae, Agriculture Victoria research agronomist Kevin Kelly and Accelerating Change project officer Harriet Bawden.

Dairy farmers in the region use lucerne as a protein-rich summer feed and to fill feed gaps in late spring or autumn. Having a higher tolerance to water stress and higher irrigated water productivity than perennial rye-grass pastures, it is 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. Getting everything right before lucerne goes in the ground is critical to not only establishing a great stand but also the highest possible return on investment.

Planning and preparation is key

Preparation for lucerne requires careful thought about crop rotations, weed management and paddock selection in the preceding seasons. Once a crop is in the ground, there is limited opportunity to remediate soil constraints or manage broad leaf weeds.

Mr McRae and Mr Nagle said five years’ production from some lucerne varieties under good management and with the right seasonal conditions was achievable, but attention to detail in preparation was key to getting this result.

A critical first step of preparation is paddock selection. Lucerne is intolerant of wet soil and poor drainage.

By selecting the right bays on his farm, with more freely draining soils and optimal surface drainage, Mr Fitzgerald has seen improved lucerne establishment and yield compared to longer and more uneven bays sown previously, which had higher incidences of waterlogging.

Grazing of lucerne must be carefully managed to avoid damaging the stand and may require taking cows on and off within a short timeframe, particularly when it’s wet.

Allocating paddocks close to the dairy is best for flexibility in grazing management. For rumen consistency, sow enough lucerne to get a grazing every day through summer (about a 25-day rotation).

One of the key focuses of the lucerne workshop was to identify subsoil constraints and discuss remediation. Two different soil pits demonstrated the impact of soil preparation on root development and resulting plant production.

A hard pan layer is commonly found throughout the Murray region, especially in duplex soils under flood-irrigated, grass-based systems. Where the soil had not been ripped to penetrate this layer, roots were noticeably shorter and fewer. This can lead to production penalties.

It is important to diagnose any subsurface constraints before sowing because by the time production impacts are noticeable, the options for remediation are often limited or not practical or economical to carry out.

Long-term planning is important when introducing lucerne to the 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.

Mr McRae discussed the importance of considering what is grown after lucerne.

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.

Understand soil’s physical and chemical properties

Even when agronomic management on the surface is good, less than ideal subsoil conditions will compromise the performance of lucerne.

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 subsoil constraints that might be present.

Participants at the workshop examined soil pits, enabling them 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 find 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.

Mr Bannan identified dispersive soil on the site, meaning the soil has a tendency to disperse, crust and seal-up, impeding the movement of water and roots.

Dispersive soils can cause waterlogging, which is detrimental to the survival of lucerne. 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 water and looking at the response.

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

Incorporate organic matter to improve soil structure

Where the need for ripping has been identified, rip to a depth that will shatter the identified physical barrier.

Ripping can help to shatter hostile soils and subsoils 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 and allowing plants to extend their roots throughout the soil, as well as allowing the movement of water and air.

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. Increasing irrigation intervals or drying-off bays completely will allow the soil to enact its drying cycle. One way to do this is to include dryland crops that are not irrigated in spring. This also provides an opportunity to incorporate organic matter.

Too much water is more damaging than too little

Ms Bawden and Mr 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 rye-grass, where water availability and price is a concern.

Research shows that the production of lucerne is linearly related to water use (to the point of meeting plant water requirements).

Irrigation management of lucerne can be more flexible than the irrigation management of some alternative forages.

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. The soil pits under Mr Fitzgerald’s lucerne revealed roots at 80 cm to 100 cm, although they have also been known to extend deeper.

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. 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.

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 United States in the coming years.

Mr McRae 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. 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 three to 10, with three having the shortest growing season and 10 having the longest.

Mr McRae suggested lucerne with higher dormancy (‘winter active’) may get two to three additional grazings or cuts for the season but fewer seasons out of the stand, due to potential damage caused by intensive grazing.

Although lucerne management can be challenging in this environment, its water use efficiency, flexibility, perennial nature and nutritional characteristics make it an important component of the dairy feed base in the region. Varieties and knowledge of the plant continue to improve, making management easier.

The resounding message of the Accelerating Change Lucerne Masterclass was that planning and preparation, with attention to detail, will ensure the best outcomes for lucerne production.

• By Amy Fay and Harriet Bawden,
Accelerating Change, Murray Dairy