Alfalfa is a perennial leguminous forage. Its growth period can be divided into six stages: seedling stage, branching stage, budding stage, flowering stage, mature stage and dormant stage. Nitrogen and potassium are the most needed throughout the growth period, followed by phosphorus. Every 1,000 kg of forage production requires 12.5 kg of nitrogen, 3.5 kg of phosphorus and 12.5 kg of potassium.

1. Base fertilizer.

    The high, medium and low soil fertility is different, so the amount of fertilizer is different. Normally, for plots with low soil fertility, 600-800 kilograms per mu, it is recommended to apply 600-800 kilograms of decomposed and fermented organic fertilizer, 6 kilograms of urea, 17-22 kilograms of diammonium phosphate, and 9 kilograms of potassium chloride per mu. For plots with medium soil fertility, with a yield of 800-1000 kg per mu, it is recommended to apply 750-1000 kg of decomposed and fermented organic fertilizer, 6 kg of urea, 15-20 kg of diammonium phosphate, and 7 kg of potassium chloride per mu. For plots with high soil fertility, with a yield of 1000-1200 kg per mu, it is recommended to apply 500-750 kg of decomposed organic fertilizer, 4 kg of urea, 13-17 kg of diammonium phosphate, and 6 kg of potassium chloride per mu.

2, Top dressing.

    The entire growth cycle of alfalfa requires high nitrogen fertilizer, but it needs to be supplemented with nitrogen fertilizer and potassium fertilizer at the same time after each cutting, which is conducive to the synchronous growth of the above-ground leaves and stems. Potassium can promote the upward conduction of cytokinin to promote the growth of aerial parts.

Practice has proved that the application of potassium fertilizer to alfalfa can prolong the growth period and increase the yield by more than 10% per mu. The amount of topdressing varies according to the level of soil fertility. Generally, it is recommended to topdress urea 4-5 kg, potassium chloride 4-5 kg, and 1-2 kg per mu for low-yield fields. For medium yield fields, it is recommended to topdress urea 3-4 kg and potassium chloride 4-5 kg per mu for high-yield fields. It is recommended to topdress 3-4 kg of urea and 3-4 kg of potassium chloride per mu.