THIS PROMOTIONAL FEATURE WAS PROVIDED BY BALLANCE AGRI-NUTRIENTS
Lucerne needs a bit of legwork to get going, but with increasingly long, dry summers, is set to become even more popular.
If you don’t get it right, lucerne can be expensive to establish, but well managed, it lasts up to eight years. Its extensive, deep roots are good at finding water, and it fixes nitrogen from the atmosphere to power its growth.
Lucerne can fix around 30 kg of atmospheric nitrogen per tonne of dry matter. For the crop to fix nitrogen, use seed with group A Rhizobium inoculum.
Sowing lucerne in spring gives it the best chance to successfully establish, beat weeds, form a healthy crown and put down roots, setting it up for the following year. It grows slower in autumn’s decreasing daylight and temperatures, making it less competitive to weed issues.
Before establishing test soil to a depth of 150 mm so you can adjust pH and nutrients to optimum levels. The optimum pH, 6.0-6.2 in the top 150 mm of soil, allows the Rhizobium bacteria to function well and fix nitrogen. It also prevents exchangeable aluminium from restricting root growth.” It generally takes about 1-2 T lime/ha, to lift pH by 0.1 units and should be applied at least 6 to 12 months before sowing, particularly if pH is low.
Lucerne is efficient at extracting phosphorus from the soil, which it needs for energy hungry processes such as photosynthesis and nitrogen fixation, as well during establishment. Olsen P levels of 15 are sufficient for Lucerne, and, according to research, it will not produce a yield response to higher phosphorus levels. To raise Olsen P, apply a soluble form of phosphorus (such as SuperPlus) at sowing to aid establishment, and then annually in spring to maintain Olsen P levels.
Depending on yield, harvesting lucerne removes more potassium than any other nutrient besides nitrogen. Silage and hay remove 20 and 15 kg potassium per tonne of dry matter respectively. Applying most of the replacement potassium after harvest, avoids luxury uptake and removal in herbage. For grazing, replacing potassium is less of a concern and easily done together with spring maintenance fertiliser. Around 25-30 kg of potassium per hectare in grazed situations is normally enough to maintain potassium at QTK levels of 6-8.
Most soils used for lucerne supply enough magnesium. If Quick Test results are under 10, add magnesium to the base fertiliser using Serpentine SuperPlus at a rate that supplies 5-10 kg magnesium/ha/year.
Sulphur, essential for protein formation, also enables lucerne to fix nitrogen, so sulphate sulphur levels should be at least 6-10 ppm. If annual rainfall is under 1500 mm, apply sulphate sulphur (found in SuperPlus) in spring at a rate of 20-30 kg S/ha. In higher rainfall areas, or if applying maintenance fertiliser in autumn, SulphurgainPlus products containing phosphorus and elemental sulphur can be used, minimising the sulphur leaching risk.
Testing herbage pinpoints micronutrient needs, rather than relying on standard lucerne mixes. Lucerne needs molybdenum to help fix nitrogen (> 0.5 ppm is the target) applied at 4 kg/ha (granular molybdenum) at sowing, then every four to five years. On pumice or sandy soils, lucerne may need 5-10 kg/ha of granular boron every four years.
With a bit of legwork, lucerne provides excellent feed, high in metabolisable energy and protein, from spring right through to autumn.