Plowing in winter is not only an important measure to increase cotton production, but also an effective method to eliminate overwintering bollworms. According to research, cotton bollworms generally spend more than 2.5 to 6 centimeters from the ground (up to a depth of 9 centimeters) to pupate overwintering, and winter plowing has a variety of killing effects on bollworms: 1 destroys the diverticulum and changes the natural state of the carcass. Reduce the eclosion rate of late spring; 2 Turn some of the worms to the surface to make them dead, frozen or eaten by natural enemies; 3 Turn some worms into the deep layers of the soil so that they cannot be normally feathered and become suffocated. Reduce overwhelming insect sources. Its technical requirements are:
First, the winter tillage time The sooner the winter tillage time is, the better, generally after the harvest of the previous crop, it must be carried out. Before the earth is frozen (the permafrost layer exceeds 5 cm), it is cultivated to prolong the weathering time and improve the pest control effect. And it is conducive to accepting more 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.
Second, cultivating the hoe and ploughing the hoe before the winter ploughing, ploughing and then smashing the smashing rake, you can store water and protect the quail, and can smash some overwintering worms. According to surveys, winter plowing in the cotton fields can suffocate 76-85.6% of cotton bollworms. After winter plowing, pupae are buried deep in the soil and the survival rate can be reduced by 86.4-92.5%. According to observations, winter plowing followed by plowing. In the spring, the water content in the 5 cm soil layer was 16.4% in the spring, but only 8.2% in the unopened soil.
Three, plough depth Winter ploughing, plough depth should be more than 10 cm; winter plough deeper, the better pest control effect.
Fourth, irrigation after irrigation Winter ploughing followed by winter irrigation or spring irrigation, not only can sink, weathering the soil, but also increase the mortality of overwintering pupae. 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 non-irrigated plots and 30-40 for non-irrigated plots. %.
In addition, due to the strong fly ability of adults of Helicoverpa armigera, winter plowing must be carried out in large areas in order to be effective; in addition to the reserved cotton prairie land, wheat fields are interplanted and orchard gaps are also required for winter plowing.
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