Yield reduction reasons and yield protection techniques of soybean continuous cropping cultivation

1. Reasons for yield reduction of continuous cropping soybean

The continuous cropping soybean plants showed slow growth, short growth, yellow leaves, fewer pods and fewer seeds, resulting in a significant decrease in yield. In the short term, continuous cropping will aggravate the harm of cyst nematode, root maggot, root rot, heart borer, gray spot and malignant weeds, and the partial consumption of soil nutrients, resulting in the deficiency of soil nutrient elements and the increase of pathogenic fungi in soil. the number of beneficial bacteria decreased, and some toxins were produced, which led to a serious decline in soybean yield and quality. In the long run, after long-term accumulation and reproduction, the density of diseases, insects and grass to a certain extent will lead to soybean yield loss and harm for many years, in which the longer the years of continuous cropping cultivation, the more serious the harm to soybean yield and quality.

2. Yield protection technology of continuous cropping soybean.

The main results are as follows: 1. In order to select suitable land for continuous cropping soybean, land selection is the key, and suitable land should be selected in accordance with the principle of "planting is not heavy, fertilizer is not thin, depression is not on duty, and avoiding diseases and insect pests". First, under the same conditions, we should achieve "planting is not heavy". First of all, we should get rid of the traditional concept of "it is better to plant than to meet the stubble". For the difference between heavy cropping and Yingyao, continuous cropping is continuous cropping and crop rotation is the next year. The yield reduction of continuous cropping on soybean is different, the yield reduction of continuous cropping is light, the yield of continuous cropping soybean is reduced by about 10%, and the yield of continuous cropping soybean is reduced by about 30%. Therefore, we should "welcome rather than heavy", and continuous cropping for more than two years is strictly prohibited. Second, under the conditions of different topography, different soil types and different fertility, black soil plots with low-lying terrain and fertile soil should be selected. Saline-alkali soil, white serous soil, sandy loam and plots with low content of organic matter are not suitable for planting. Third, continuous cropping should be avoided in the plots with serious diseases and insect pests, especially those with obvious harm, such as cyst nematode, Sclerotinia sclerotiorum, dodder and so on.

2. The comprehensive control techniques of agricultural measures and biological and chemical measures should be considered in the selection of disease-resistant varieties. The key point is to select the seeds well, and according to the local characteristics of accumulated temperature, soil, and the occurrence of diseases and pests, we should select varieties with strong growth potential, more luxuriant, like fertilizer and water, disease and insect resistance, and strong resistance to diseases and insect pests, and do a good job in seed chemical treatment to reduce the harm of diseases and insect pests.

3. The scientific application of two fertilizers and continuous cropping led to the single consumption of nutrients in the soybean field, resulting in the loss of balance of nutrient elements in the soil and the imbalance of nitrogen, phosphorus and potassium, resulting in a reduction in yield. Therefore, the supplement and regulation of soil nutrients is an important technical measure to reduce the harm of continuous cropping. We should combine agricultural fertilizer and chemical fertilizer, increase the amount of agricultural fertilizer, combine nitrogen, phosphorus and potassium micro-fertilizer, increase the amount of trace elements such as potassium, zinc, copper and molybdenum, and use soybean multi-element compound fertilizer. The specific amount should be determined according to soil fertility and cultivation level. in general, diammonium 10kg and potash fertilizer 5kg are used as seed fertilizer and urea 5kg as topdressing fertilizer. In barren land with poor growth, urea 0.75~1kg can be sprayed with water per mu at flowering stage. In the plot using multi-element compound fertilizer, applying potassium fertilizer 2.5kg while applying 20kg compound fertilizer per mu, a large amount of lime soil fertilizer and plant ash could be applied in the land with serious potassium deficiency, and at the same time, the mu was sprayed with potassium dihydrogen phosphate 0.15kg with water at the flowering stage, and sprayed again every 7 to 10 days. The application method of trace elements can be foliar spraying or seed treatment. The common dosage of micro-fertilizer for seed dressing is: borax, 0.4g for 1kg seed, 0.5g for ammonium molybdate, 0.5g for 1kg seed, 5g for zinc sulfate and 1kg seed.

4. To strengthen the prevention and control of root maggots and other underground pests, potassium mixed with phosphorus 2kg or 3% carbofuran granule 4~5kg can be used in fertilizer per mu; to control soybean heart-eating insects, aphids, red spiders, meadow borer and other ground pests, dichlorvos, avermectin and other corresponding pesticides can be selected respectively; carbendazim, methyl topiramate, agricultural streptomycin and other corresponding pesticides can be used to control diseases. The prevention and control of dodder can be sprayed at flowering stage with 48% dimethoamine emulsion 50 ml mixed with water into 150 × 200 times dilution.