Detailed Explanation of Key Points for Chinese Milk Vetch Green Manure Incorporation Planting Technology

(Agricultural Wealth Network) Chinese milk vetch (Astragalus sinicus, also known as honghuacao) is the main winter green manure crop in rice paddies in our province. The Chinese milk vetch varieties suitable for planting in our province are mostly early-flowering and mid-flowering varieties. Early-flowering varieties include Leping seed, Changde seed, Ganzi No. 1, etc.; mid-flowering varieties include Yujiang Large-Leaf seed, Pingning No. 3, Fengcheng seed, Makou seed, Anhui Large-Leaf Green, Minzi No. 6, etc. 1. Field plot and crop rotation arrangement: Choose fields with level surfaces and convenient irrigation and drainage. In crop rotation arrangement, avoid scheduling on the latest rotation to prevent frost damage after rice harvest. 2. Seed treatment: Before sowing, sun the seeds at noon on a sunny day for 4-5 hours. After sunning, mix the seeds with fine sand at a 2:1 ratio, put them into a woven bag, and rub the seeds. Then, use 5% salt water to select seeds, removing diseased grains and empty shriveled grains. Soak the selected seeds in 0.2% potassium dihydrogen phosphate solution for 10-12 hours, or in 0.1-0.2% ammonium molybdate solution for 12-24 hours. After soaking for sufficient time, remove and air-dry, mix with calcium magnesium phosphate fertilizer (in newly expanded planting areas, use about 0.5 kg of rhizobium peat per mu for seed mixing), and then sow. 3. Timely sowing: Generally sow from mid-to-late September to early October. If sown too early, the rice-fertilizer symbiotic period is too long, and seedlings are thin and weak; if sown too late, they are prone to freezing damage, and there are insufficient overwintering seedlings. In production, it is often done after the late rice has full ears and is nodding. If sowing in vigorously growing hybrid late rice fields, sow 20-25 days before late rice harvest to facilitate rice maturity and vetch seedling emergence and growth. The sowing rate per mu is generally 1.5-2 kg, and the field should be kept moist during sowing. For deep-foot fields and cold-water fields, stop water and dry the field 2-3 days before sowing; for sandy fields, sow in shallow water, and drain after seeds germinate; for general fields, when drought causes the field surface to crack and turn white, irrigate once 1-2 days in advance, let it drain naturally, and keep the soil moist. After late rice harvest, cover with rice straw for cold protection. 4. Water management. Mainly open three ditches: in addition to opening waist ditches and surrounding ditches at the late tillering stage of late rice combined with field drying, generally open a straight ditch every 10-15 meters or so before sowing, connected with the surrounding ditches, so that all ditches are interconnected and no water accumulates after rain. Water management should be based on the field plot and soil quality. Fields with heavy clay soil should be properly dried to achieve soft and muddy soil, so as to avoid seed sinking and bud rot; sandy soil, to avoid soil being too dry after seed germination and causing bud scorching, should be sown in shallow water and drained after seeds germinate; in areas with good soil tilth and convenient irrigation and drainage, the standard can be soft soil surface with a water layer at germination and moist soil surface without a water layer at emergence. After seeds germinate, no water should accumulate during the intercropping period. After rice harvest, promptly irrigate with running water to prevent drought, keeping the field surface from turning white; after spring warms up, pay attention to clearing ditches to prevent waterlogging. 5. Fertilization management: Mainly apply three fertilizers: first, at rice harvest or when the first true leaf appears, apply 5 kg of potassium sulfate fertilizer per mu; second, before covering with rice straw, apply 25 kg of calcium magnesium phosphate fertilizer per mu; third, around the Spring Festival, that is, from mid-February to early March, apply 2.5 kg of urea per mu. 6. Pest and disease control: The main pests of Chinese milk vetch include aphids, leafminers, thrips, and stem-boring flies, which can be sprayed with 20% dimethoate 1000-2000 times diluted solution. Where water sources are convenient, if aphids or stem-boring flies are found at the seedling stage, irrigate to submerge the leaf tips for 3 hours and then drain to kill the insect flies. The main diseases are powdery mildew and sclerotinia, which can be controlled with lime sulfur mixture (0.3 degrees Baume). 7. Timely harvest: Chinese milk vetch should be harvested in time from full bloom to early pod stage. The yield of Chinese milk vetch should be controlled within 2000 kg per mu (within the 4-curve range); excessively high yield will cause excessive absorption of soil nitrogen fertilizer, affecting the growth of the next crop. 8. Timely incorporation and retting for return to the field: Timely incorporation and retting is the last step to improve the yield and fertilizer efficiency of Chinese milk vetch, and it is often easily overlooked in production. If incorporated and retted too early, the yield is not high, the nitrogen content of fresh grass is low, the water content is high, and fertilizer efficiency is low. If incorporated and retted too late, although the yield is high, the cellulose and lignin in the fresh grass increase, the plants age, which is not conducive to decomposition and decay, and fertilizer efficiency is also low. Moreover, the decomposed organic acids and large amounts of carbon dioxide and hydrogen sulfide gas will affect the survival and tillering of early rice seedlings. It should be controlled to plow when 60-70% of flowers have bloomed, and at the same time broadcast 15-20 kg of lime per mu to promote accelerated decomposition.