Control techniques of soybean root rot in Heilongjiang Province

Root rot is common in soybean producing areas in Heilongjiang Province. the general diseased plant rate in the field is 30%-40%. The diseased plant rate in low-lying land and continuous cropping land is more than 70%, and the highest seedling death rate is more than 15%. The occurrence in the eastern region is more serious than that in the western region, and the occurrence is the most serious in the eastern soil moist area. In general years, the rate of diseased plants in the early growth stage (before flowering) of soybean is about 75%, the disease index is 35%-50%, and the disease index can reach more than 60% in rainy years.

The incidence of soybean root rot mainly depends on the number of bacteria in soil, soil physical and chemical properties, soil temperature and humidity, plant resistance and so on. In order to better control soybean root rot, control must be carried out according to these conditions. Change the previous way of using only chemical agents for control, and adopt comprehensive control measures of the combination of agricultural measures and biological agents.

1. Avoid continuous cropping and scientific rotation. Because the root rot pathogen belongs to soil habitual bacteria, it can rot in the soil. Under the condition of continuous cropping, the pathogen grows well, propagates rapidly, the number of bacteria in the soil increases, and the disease is serious. In addition, the changes of root exudates, stubble decomposition and rhizosphere microorganisms in soybean continuous cropping land worsened the soil environment, destroyed the normal physiological activities of soybean roots, reduced the physiological activity of soybean roots, and destroyed the symbiotic nitrogen fixation system. it inhibits the absorption capacity of roots, weakens plant metabolism and slows plant growth. Therefore, the longer the continuous cropping years of soybean, the more serious the incidence of root rot.

At present, the fundamental way to solve the harm of soybean replanting is to adhere to the system of rotation with Gramineae crops for more than 3 years. However, under the current conditions of taking farmers as production and management units, it is inevitable for soybean to be heavy and stubble. Therefore, we should distinguish between stubble and stubble, reduce stubble as much as possible, and meet stubble properly. Pingchuan land and Erwa land with high content of organic matter can be selected to plant soybean, and the continuous cropping can only be repeated for one year, and the former corn, linen and flax are the best.

two。 Select the land scientifically according to the physical and chemical properties of soil. The soil texture is loose and the permeability is good, such as sandy loam, light loam and black soil are lighter than white serous soil and clay soil with poor permeability, and the disease of fertile soil is lighter than that of barren soil.

3. Adjust the sowing date according to the soil temperature and humidity. The optimum temperature for soybean seed germination and seedling growth is 20-25 ℃. The emergence of soybean seedlings is seriously affected when the temperature is below 9 ℃. Therefore, the sowing time soil temperature is low, the disease is serious. The soil water content is large, especially in the low-lying tide wetland, the growth of soybean seedlings is weak, the disease resistance is poor, it is easy to be infected by bacteria, and the disease is serious.

4. Adopt scientific cultivation methods. In general, the disease of soybean cultivated in ridge cultivation was lighter than that in flat cultivation, and the disease in soybean cultivated in large ridge was lighter than that in soybean cultivated in small ridge. The reason is that the ridge cultivation can cultivate the soil, which makes the soil loose, the permeability is good, and the soil water content is low. On the flat land, because the soil is hardened and prone to waterlogging, the soil water content is high, which is beneficial to the propagation of bacteria and infect the roots.

5. Choose the appropriate sowing depth. Sowing depth of soybean directly affects the unearthed rate of seedlings, sowing too deep, coupled with low ground temperature, slow growth of seedlings, tender tissue, lengthening of underground roots, roots are easy to be infected by bacteria, which aggravates the disease.

6. The method of balanced fertilization was adopted. The level of fertilization also has a great influence on the occurrence of root rot disease. Heilongjiang Province generally attaches importance to phosphate fertilizer, but neglects the application of nitrogen fertilizer, potassium fertilizer and trace elements, rarely uses farm manure, and the content of available nitrogen and potassium in the soil of continuous cropping plots decreases. the content of trace elements such as boron, zinc and molybdenum decreased, nutrition imbalance decreased, resulting in the decline of crop disease resistance. Balanced fertilization through scientific soil testing formula technology and reasonable supplement of nitrogen, phosphorus, potassium fertilizer and trace element fertilizer can significantly improve the resistance of soybean to root rot disease. The application of 1000kg organic fertilizer per 667m2 can increase soybean yield by more than 10%.

7. Control insect pests and reduce the chance of germs invading from the insect mouth. In general, there is harm to root miners, which is beneficial to the occurrence of root rot diseases. the higher the plant rate is, the more serious the disease is, and vice versa.

8. Use reasonable chemical herbicides. The good application of chemical herbicides in soybean field can play a good role in killing weeds in soybean fields, but some chemical herbicides can cause drug damage to soybean seedlings and hinder the growth of soybean seedlings due to improper application methods and dosages. at the same time, it also aggravates the occurrence of root rot.

9. Select disease-resistant varieties. The varieties with light disease, high yield, high quality and strong stress resistance can be selected. Practice has proved that the selection of disease-resistant or disease-tolerant varieties is an effective measure to reduce the effect of continuous cropping on soybean yield and quality. In addition, reasonable collocation of different varieties and rotation of varieties should be done to reduce the harm of continuous cropping. In particular, Suinong 14, Suinong 15, Hefeng 25 and Hefeng 35 were more serious in root rot and cyst nematode disease, and Suinong 10, Xin Hefeng 25 and Kenjiandou 23 could be selected.

10. Increase the amount of broadcast. For continuous cropping plots, it is necessary to ensure the number of soybean seedlings and give full play to the role of the population in increasing production, so as to reduce the extent of yield reduction; to appropriately increase the sowing amount, generally increase the sowing rate by 8% to 10% compared with normal soybeans, and improve the sowing quality and increase the number of seedling protection plants.

11. Fine farming. Soybean continuous cropping land, especially continuous cropping in successive years, leads to soil compaction and consolidation, lack of reasonable aggregate structure and decrease of fertility. Fine soil tillage can destroy the stratified layer, create good soil conditions for the growth and development of soybean roots, and effectively reduce the harm of diseases and insect pests. In soil tillage, we should adhere to the soil tillage system of the combination of loosening, turning, harrowing and rotation, vigorously popularize the subsoiling tillage method and improve the growth environment of soybean. In addition, after seed dressing with common soybean seed coating agent, the effect can only last for 15 to 25 days, so it is more important to cultivate soil in time, especially in the case of death caused by underground root damage, in order to promote the formation of new lateral roots at the base of aboveground stem and replenish fertilizer and water in time, otherwise the seedlings will die without lateral roots.

twelve。 Chemical control. Seed dressing with chemicals can postpone the infection period. 35% of the seed coating agents have a short period of validity, only 25 to 30 days; because of the short validity period of fungicides, seed coating agents made of various fungicides can only protect the main root, protect seedlings, postpone infection and reduce harm. Common methods: (1) seed dressing with soybean seed coating agent containing carbendazim, thiram and insecticide, seed coating agent 1000~1500m1 per 100kg seed. (2) seed dressing with 2.5% suspension seed coating agent 150ml and 20% apron seed dressing agent 40m1 per 100kg seed, the control effect of biological agent is better than that of chemical agent. First, biological control broke the balance of the flora environment in the soil and reduced the infection of harmful bacteria to the roots; second, it acted for a long time, which lasted for more than 70 days; and third, it had strong pertinence. It has a strong inhibitory effect on the main obstacle factors of soybean continuous cropping-Penicillium and its toxin and Fusarium F6, the pathogen of soybean root rot. The experiment of biological seed dressing of 133 hectares of soybean in Hulin region of Heilongjiang Province for many years was carried out in 2006. The seedling death rate of seed dressing with seed coating agent was more than 10%, and that of biological seed dressing was less than 5%. In particular, the seedling death rate of seed dressing with seed coating agent for continuous cropping for 7 years is about 30%, while that of biological seed dressing is about 3%. The method is to treat each 100kg seed with 2% Keduke (Ningnanmycin) water agent 1000~1500ml.