Lucerne, also called Alfalfa (Medicago sativa L.), is known to be the oldest cultivated crop specifically grown for animal feed. Academic literature traces its origin back to Central Asia, but it is currently grown in most parts of the world under a wide range of climatic conditions to produce various forms of feed for a number of domesticated farm animal species. The well-developed taproot system of lucerne plants provides access to water reserves deeper than 5 metres in some recorded cases, enabling it to survive extended periods of drought.
Management practices for lucerne production need to be in place before establishing the crop itself. This mainly entails (i) the choice of a suitable land area, (ii) nutritional analysis of the soil, (iii) corrective measures based on these results, and (iv) proper seedbed preparation. The weed spectrum must be addressed by either eradicating, or at least limiting, the amount of viable weed seed that may interfere with the growth and development of a newly planted lucerne crop. If applicable, the planned irrigation system must also be correctly laid out to ensure its efficacy.
Recent advances in chemical weed control now allow more frequent planting and establishment timeframes, as opposed to the traditionally limited periods in early spring and late summer. Active ingredients of herbicides such as bromoxynil (nitrile), propaquizafop, imazamox (40 SL), and paraquat can be applied at various growth stages throughout production. When considering the nutritional requirements of lucerne, various academic strategies have been trialed and tested in order to achieve optimal yields. Yield is normally measured in tonnes per hectare (t/ha), although many farmers and producers also refer to the number of bales (either square or round) per unit surface area. Average data collected under local South African conditions under irrigated production indicate possible yields of 30–55 tonnes of wet mass per hectare per season, resulting in an estimated 15–25 t/ha of dry material. Figures for non-irrigated (dryland) production vary greatly depending on rainfall, with an average final dry yield of 4–8 t/ha per season. It should be noted that maximum yield in terms of wet and/or dry mass does not always translate into maximum financial return.
Table 1 - Amount of nutrient elements removed from the soil per ton dry material lucerne produced according to Undersander et al 1994:
Because many nutrients are removed from the soil during production, it is generally not recommended that a fertilisation program be based solely on nutrient removal values. Fertilisation should rather be planned according to soil analyses, as this provides the most reliable method for preventing nutrient deficiencies.
Potential average yields of 15–25 t/ha of dry matter per season under irrigation are expected to vary between different production systems and climatic regions. Yield will also depend on the dormancy group of the specific variety or cultivar used, as well as the nutritional status of the soil and how effectively this is maintained.
Applications of foliar sprays in the form of specifically formulated products have been shown to enhance overall performance in terms of yield and quality in lucerne fields. Under optimal environmental conditions, a significant proportion of the active ingredients in these products assist biological, physiological, and biochemical processes within the plant.
Table 2 - Guidelines for applying phosphorus (P) and potassium (K) based on soil analyses, published by The National Lucerne Trust (NTL):
From a plant nutrition perspective, the most important macro- and micro-elements are supplied when using a weekly or bi-weekly foliar spray program. Foliar applications of phosphorus (P) and potassium (K) should be applied within the first two weeks after cutting. In addition, SPOREKILL® is added with the first foliar application to combat possible secondary disease infections that may occur after bruising of new growth during cutting or harvesting.
FOSFASPRAY is a water-soluble nutrient mixture with phosphate as the main component, containing 253 g of phosphorus per kilogram of formulated product. Phosphate plays an important role in photosynthesis and is a key structural component of plant cells. It also stimulates root development, thereby improving water and nutrient uptake.
POTASPRAY contains 179 g of potassium (K) per kilogram of concentrated, water-soluble product. Potassium is well known for its primary role in the translocation of water and dissolved nutrients throughout the vascular system of plants. When potassium supply is reduced, intracellular movement of nitrates, phosphates, calcium, magnesium, and amino acids is restricted.
HYGROBUFF 4 is added as a buffering agent to optimise the pH of the spray mixture and should always be added first, followed by the nutrient components and other products in that order.
ASCO-GRO seaweed extract contains auxins and cytokinins (plant growth hormones in amino acid form) that enhance growth and provide relief from plant stress conditions such as extreme temperature fluctuations.
It is generally accepted that the ratio between calcium (Ca) and magnesium (Mg) in soil and plants should be maintained at a cation composition of approximately 65% to 25% on a milliequivalent percentage basis. CALMABON LIQUID is ideally suited to meet these requirements. Excess calcium may result in boron deficiency; the added boron in this formulation assists in preventing this problem.
Nu-Film P sticker is added last to ensure maximum uptake of the applied components through the leaf cuticle and to provide protection against wash-off caused by rain or irrigation water.
Table 3 - Advised foliar spray application program with water soluble fertilizers on lucerne:
Key Strengths of Lucerne
• Drought tolerant: Lucerne has a deep rooting system that allows access to water and nutrients beyond the root zone of many other crops.
• Soil builder: As a legume, lucerne increases soil nitrogen (N) and organic matter, improving soil structure and fertility.
• Versatile: Can be used for on-farm grazing, forage conservation, or for producing silage or hay for sale.
• Perennial crop: Lucerne produces green feed for much of the year, with a productive stand life of 5–7 years.
• Wide adaptability: Lucerne performs well across a range of climatic and soil conditions.
• High yielding: Lucerne produces approximately 12–20 t DM/ha/year.
• Excellent feed quality: Lucerne can be used to improve animal performance.
• Strong global focus on lucerne breeding: Continuous breeding efforts ensure the availability of new varieties with improved yield potential and enhanced disease resistance.
