Deep plowing in autumn and winter is an important measure to ensure the increase of cotton yield, and it is also an effective method to eliminate overwintering bollworms. According to studies, the cotton bollworm is generally wintering at 2.5-6 cm (up to 9 cm deep) from the ground. Autumn and winter plowing has a variety of killing effects on the bollworm: First, it destroys the diverticulum and changes the natural state of the carcass. Reduce the emergence rate of late spring; Second, turn some insects to the surface to make them dry, frozen or eaten by natural enemies. Third, turn some insects into the deep layers of the soil so that they cannot be normally feathered and become bored. Dead, thus reducing the source of overwhelming insects. Its technical requirements are:
1. Deep plowing time. The better the autumn and winter tills, the better the crops will be harvested after harvesting. Before the earth is frozen (more than 5 cm in the permafrost), it will be cultivated to prolong the weathering time, improve the pest control effect, and facilitate multi-admission. Rain and snow. After the land is frozen and ploughed, not only the farming is difficult, but also the quality of the cultivated land is reduced, and the pest control effect is also poor.
2. Combine cultivation. Before the ploughing, the hoe should be smashed again. After ploughing, the smashing and smashing can be done. The water can be stored and the squat can be killed. According to surveys, cotton fields can suffocate 76% to 85.6% of cotton bollworms before they are cultivated. After cultivation, the pods are buried deep in the soil, which can reduce the survival rate by 86.4% to 92.5%. According to Shandong Academy of Agricultural Sciences Observed, after the winter ploughing followed by the depression, the water content in the 5 cm soil layer in the spring was 16.4%, but only 8.2% in the unfinished soil.
3. Plow depth. Deep plowing in autumn and winter, the plowing depth should be more than 10 cm; the deeper the plowing, the better the pest control effect.
4. Irrigation after cultivation. After cultivating and then irrigating, not only can the soil sink, but it can also increase the mortality rate of overwintering crickets. According to a study by the Chinese Academy of Agricultural Sciences, when the relative soil moisture content is 40%, the mortality rate of Helicoverpa armigera is 35.7% and the emergence rate of adult is 40%. When the soil moisture content is 70%, the mortality rate of Helicoverpa armigera is 46.7%. The eclosion rate was 33.3%; when the soil moisture content was saturated, the mortality rate of pupa was 100%. According to another data, the wintering mortality rate of cotton bollworms is about 80% for winter plowing and winter plowing, and the wintering mortality rate is 60%-70% for plots with no tillage, and only 30% for non-irrigated plots. -40%.
In addition, due to the strong fly ability of the adult Helicoverpa armigera, autumn and winter ploughing must be carried out in large areas to be effective, in addition to the reserved cotton day, the wheat field interplanting rows, orchard gaps also need to fall and winter plough.
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