Maximising production and stand life of lucerne

Peter Tame, AusWest Seeds, Southern QLD & Northern Rivers NSW

Lucerne, whether it is irrigated or dryland, needs to be well managed to maximise its production and persistence. Adding grazing animals adds another level of complexity to the management. Planning is essential to ensure good establishment, a productive stand and longevity.

Paddock Preparation
The success of a lucerne stand begins with paddock selection and preparation to ensure a good establishment of new seedlings is achieved. Many would think this relates to preparation of a fine soil tilth for good seed/soil contact and forget to include weed control.

What do we determine to be a weed?

In lucerne stands grasses should be considered potential weeds, not just broadleaf plants. So to help reduce the risk of failure, it is important to consider going through a thorough cleanup phase first. This can be achieved by growing crops or pastures which have the ability to withstand herbicides that control undesirable/unwanted plants in the new lucerne stand. There are a number of herbicides that will control grass and broadleaf weeds in this cleanup phase. Consult your local chemical suppliers for further information.

Paddock Selection
Lucerne prefers free draining soils. Soils that are heavy (have a high clay content) and retain high levels of soil water can pose a problem. In the SE corner of Queensland these types of soil often have the added issue of Phytophthora and Colletotrichum Root Rot. Flooding often results in partial or complete loss of lucerne stands.

Titan 7 lucerne | AusWest & Stephen Pasture Seeds
A healthy lucerne stand

Varietal Selection

Varietal selection is a critical component of maximising the production of your lucerne stand. All lucerne’s are summer active – producing more in summer than winter.

The rating numbers (dormancy) associated with the varieties relate to the extent of their winter activity. The lower the number indicates less production occurs in winter. In colder environments, plant stands will go dormant or slow their growth through the colder months of winter.Those with a winter rating of 9 or 10 are more winter productive that those with a 3 or 5 score. Having said that, even these higher rating varieties still produce the bulk of their annual production in the warmer spring and summer months.

While it’s possible to produce hay from all varieties of lucerne, there are some varieties more suitable to hay production than others. For farmers looking to graze their lucerne stands, varieties with a rating 3 to 7 have lower crowns which are less likely to be damaged by animal hooves.

Disease and insect resistances are the most important considerations when selecting varieties, especially under irrigation and in the regions where high humidity is common. Diseases such as Colletotrichum Crown Rot and Phytophthora Root Rot are a major soil borne disease which affect lucerne.

Some of the more common leaf disease are Stemphylium leaf spot and Leptosphaerulina (Pepper spot). This is a feature of lucernes with higher winter activity scores around 9 to 10. Stands with these diseases can be cut and removed. As the infected leaf matter drops from the plant and volumes build on the soil surface so does the incidence of spores. Removal of the lucerne helps reduce the volume of infected leaf matter on the ground and the incidence of water splashing spores off the old dropped leaves onto the new plant growth. If the infections are recurring they can be controlled with timely fungicide applications.

Blue Green and Spotted alfalfa aphids are the main insect pests. Fortunately most new varieties have good resistance to these insect pests. These insects can reduce plant stands and lucerne quality. Control of some of these pests can be by biological control. However there are many more species of insects that attack lucerne and affect its quality and yields. Monitoring is necessary and if populations explode insecticide controls can be used.

When inoculating lucerne seed with rhizobia prior to planting the addition of seed treatments with fungicide such as Apron and insecticides such as Poncho® Plus are recommended to control diseases such as Pythium Root Rot and insects such as Red Legged Earth Mite and Blue Oat Mite. Our Titan 7 and 9 varieties are treated with SowEasy KickStart™ which contains Poncho® Plus.

Plant Stand

The initial plant stand is always going to be the best stand. Lucerne plant numbers do not increase over time. There are a number of publications suggesting various plant stands per m2 for different conditions and regions (et. al K Bullen, M Lattimore). With good irrigation, the plant stand should be higher to maximise the productivity of the block.

Higher seeding rates also help provide better weed competition and finer stems.

- Good Irrigation 150 to 200 plants /m2
-  Dryland 30 – 40 plants /m2

Cutting Intervals

If you are producing hay, the cutting intervals will need to be longer in winter than the warmer months when the plant is growing more actively. The timing of cutting a stand is a balance between weather conditions, maximising the plants carbohydrate levels, quality, yield, stem thickness and its effect on persistence. Previous indicators for cutting times were looking for a low level of flower development.

As this is not a consistent indicator, farmers should look for new shoot development at the base of the plant. Cutters should be set above these new leaves as they are the next crop of lucerne.

Grazing Intervals

If the operation is built on grazing lucerne the management of the grazing intervals should also be monitored by the new shoot development. Avoid over grazing lucerne stands and set stocking by incorporating rotational management.

Irrigation – Water Use

Most farmers apply irrigation immediately after cutting and baling. Actively growing plants through the warmer periods of the year are more productive then. Irrigation requirements are dependent upon the water holding capacity of the soil, in-crop rainfall events, temperatures and humidity. In the cooler months multiple applications may not be needed.

The Water Use Efficiency (WUE)of lucerne is 0.73 ML / tonne of lucerne as hay (et. al K Bullen).

Nutrient Requirements

Soil nutrient levels and their availability to the plants are vitally important to production levels. Soil pH is also important with a preferred range of 6.5 to 8.0. These need to be monitored through soil testing to ensure minimum levels are maintained. Granular forms are available in many blends. Liquid applications are good for quick response. Molybdenum may be an advantage in acid soils for improved nodulation and hence Nitrogen fixation.

Macro Nutrient removal in hay production is:

Nitrogen 25 kg /tDM  Phosphorous 2.5 kg/tDM
Potassium 20 kg/tDM  Sulphur 2.5 kg/tDM

Average irrigation yields are 15 t /ha. So at that rate nutrient removal would be:

Nitrogen 375 kg /tDM  Phosphorous 37.5 kg/tDM
Potassium 300 kg/tDM Sulphur 37.5 kg/tDM 

Lucerne is a good source of protein fodder and is widely used in animal production systems as hay, silage, cut and carry or grazed. Export lucerne hay is also an important market for Australian producers. It is a very reliable form of production and quality is paramount to meet the various end user requirements. 

Production and persistence can be influenced by many factors from paddock selection and preparation, variety selection, weed and pest control and stage of cutting.


References:

Mary Anne Lattimore, 2008, “Producing Quality Lucerne Hay”
Ken Bullen, 2002, “Lucerne Management Handbook 4th Edition”
JS Glendinning, 1990, “Incitec Fertiliser Handbook”
M Stanley and R Christinat, 1994,” Success with Dryland Lucerne”

Damaged lucerne | AusWest & Stephen Pasture Seeds
This second photo shows: Encroachment of summer grass, Phytophthora root rot, weak lucerne plants, plants at various stages of growth, poor plant stand and open gaps 

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