What are the main field management measures for alfalfa after cutting?

    Since late June, alfalfa cutting has been drawing to a close across our city. Strengthening field management after cutting is the key to achieving another high yield in the next cutting. Agricultural departments at all levels and agricultural technicians should take measures to organize and carry out field management after alfalfa cutting. The main measures are as follows:

    Irrigation: Irrigate immediately 3-5 days after cutting once the stubble wounds have healed. Alfalfa has a well-developed root system, with the taproot penetrating 3-6 m into the soil, enabling it to absorb water from deep soil layers. However, to ensure high and stable yields of alfalfa, irrigation is an important measure. The water consumption of alfalfa is generally calculated at 800-900 jin of water per 1 jin of dry matter produced. Therefore, irrigation during severe drought seasons and after each cutting can greatly increase yield. Once alfalfa plants are established, they grow fast, yield high and require large amounts of water; after branching, the soil needs to remain moist. In arid areas, irrigation can be carried out where conditions permit, by furrow irrigation or sprinkler irrigation. Irrigating to replenish soil moisture after each cutting when drought occurs can increase the annual grass yield by more than 30%. In the first year after sowing, alfalfa water use is generally 200 m3, which is 50% of the water use of grain crops in this region. Thereafter, as the alfalfa root system extends and its ability to absorb deep soil water increases, water use shows a declining trend year by year. Surveys show that water use in the second year is 70% of the first year, and water use in the third year is 50% of the first year.

    Topdressing: Because alfalfa has a relatively high biological yield and consumes large amounts of nutrients, topdressing must be carried out after each cutting. The main types used are phosphate and potassium fertilizers or compound fertilizers, generally applying 6 kg of available phosphorus, 7 kg of available potassium and some trace element fertilizers per mu. After cutting, broadcast on the soil surface or apply in furrows, then irrigate. Alfalfa has root nodules that can provide nitrogen nutrition to the roots, but in poor wasteland soils with too low nitrogen content, apply 5-10 kg of urea after rain. At the seedling stage or after green-up, large amounts of phosphate and potassium fertilizers are needed. In addition to applying 50-60 jin of superphosphate per mu as base fertilizer before sowing, phosphate fertilizer also needs to be topdressed once each year, and the application rate of potassium fertilizer is about 20 jin per mu to ensure normal growth of alfalfa. The large number of rhizobia in alfalfa roots can effectively fix nitrogen, but nitrogen is needed at the seedling stage before root nodules have formed. After seedlings become established plants, to improve quality and yield, appropriate topdressing is still needed, especially large amounts of potassium fertilizer, to promote nitrogen fixation and absorption. In a topdressing experiment on two-year-old alfalfa, applying nitrogen fertilizer alone did not significantly increase grass yield. However, applying nitrogen, phosphorus and potassium at a ratio of 1:2:2 increased dry hay yield by more than 30%. This indicates that the well-developed alfalfa root system has already formed a large number of root nodules, and topdressing should focus mainly on phosphate and potassium fertilizers. Applying alfalfa compound fertilizer at 30-40 kg per mu can be done in a single application at green-up. It can also be applied in two split applications, once at the green-up stage and once after the third cutting of grass, with half the amount each time.

    Chemical control: Monitor the population and occurrence trend of aphids on the second cutting of alfalfa. For areas with severe occurrence, based on overall monitoring, carry out timely chemical control about 15 days after emergence of the second cutting. Options include 5% imidacloprid wettable powder at 1500 times dilution, or 4.5% beta-cypermethrin + acetamiprid emulsifiable concentrate at 1500 times dilution, or the biological pesticide BtA at 1000 times dilution for spray control.