There are various techniques to assess when lucerne is ready to cut. Many other factors must also be taken into account, including the location you are in (i.e. southern QLD versus Tasmania) which will determine the rotation length between cuts in different seasons, the dormancy class you are growing and of course, the prevailing weather conditions!
Plant growth stage can be a very accurate predictor of cutting time. Crown shoots are an excellent guide for determining cutting time, as flowering is controlled by day length and different dormancy classes and varieties may produce new crown shoots before buds or flowers appear in spring or autumn. Targeting the new crown shoot regrowth when it averages around 2cm is considered optimum.
The “yield-quality trade-off” again is critical when determining the optimum time of cutting:
Cutting height should be as low as possible without damaging the crowns or new shoots. It is important however that enough stubble is left to ensure the plant-material is off the ground for aeration and to stop ground moisture moving up into the windrows. It is suggested that 7-10cm is ideal.
Cut lucerne when new crown shoots are at least 2cm long but below mower height (7cm in this example) to ensure persistence.
Making good quality lucerne hay is a skill that requires experience or good advice from experienced people, a good environment, good organisation, motivation, commitment and dedication with good reliable equipment.
Based on nutrient removal, lucerne should be fertilised to maintain its nutrient requirements. Nutrients that are removed per tonne as hay:
Phosphorous (P): 2–3kg
Potassium (K): 15–20kg
Calcium (Ca): 13–17kg
Sulphur (S): 2–4kg
Maintain visual observations of stand health and if unsure take follow-up plant tissue tests to identify problems, particularly for micronutrient status such as Boron and Molybdenum.