Characteristics of high-yield insect-resistant cotton potash application

In recent years, the development of transgenic cotton in China has developed rapidly, which has played a key role in restoring and promoting the development of high-yield and stable cotton planting in China. At present, the planting area of ​​insect-resistant cotton has exceeded half. It has been found that there are some variations in the growth characteristics of insect-resistant cotton, including the characteristics of nutrient absorption and utilization, how to recognize these changes, and then meet their needs in field management. To this end, experts are invited to introduce the potassium nutrition characteristics of insect-resistant cotton and the rational application of potassium fertilizer to everyone, for reference only.

The source-sink relationship of transgenic Bt cotton is dysfunctional, which is highlighted by the problem of premature aging. Due to the introduction of the insect resistance gene (Bt), the new insect-resistant gene brings additional physiological consumption to the cotton plant, such as the increase of the boll weight of the plant. Both the source and the root amount decreased, and the root physiological activity was weak. Especially in the late bell stage, the physiological activity of the roots of the insect-resistant cotton decreased, and the root system was the basis for the robust growth of the whole cotton plant. The activity of the above-ground organs can be enhanced, such as high bell-forming rate per plant, early bell ringing, and high ringing rate in the inner and lower parts. As a result, insect-resistant cotton is generally easy to show due to the imbalance of source-sink relationship. The problem of premature aging. In addition, the carbon and nitrogen metabolism of insect-resistant cotton also appeared to be dysregulated after the bell-bearing period. The roots of the insect-resistant cotton were also strong in the early flowering and full-flowering stages, showing strong nitrogen metabolism. After that, the absorption of the "roots" and assimilation of transport functions Lower, also shows premature aging. It can be said that the imbalance of source and sink relationships is the direct cause of the premature aging of insect-resistant cotton. Premature reduction of root function and imbalance of carbon and nitrogen metabolism are the root causes of premature aging of cotton plants.

Insect-resistant cotton is sensitive to the supply of potash fertilizer. In production, agricultural technicians and cotton farmers have found that insect-resistant cotton is more prone to potassium deficiency than conventional cotton. It has been proved by experiments that insect-resistant cotton (such as new The dry weight of cotton 99B) is significantly reduced, and the reduction is 50% to 60% lower than that of conventional cotton (such as Zhongmian 36, 35). The main reason for the resistance of insect-resistant cotton to low potassium is root morphology and absorption. Reduced potassium capacity. With the large-scale promotion of transgenic insect-resistant cotton in production, the current situation of potassium deficiency in cotton fields is even more important. Moreover, the scientific and technological community initially believes that potassium deficiency may be one of the important reasons for the premature aging of cotton. Because some fertilization test results in recent years show that sufficient supply of potassium fertilizer can delay the senescence of leaves, some test results also prove that sufficient potassium supply in the critical period can extend the growth period of cotton bolls by about 25 days, and increase the weight of single bolls by 0.2-0.5 grams. This shows that reasonable application of potassium fertilizer can prevent premature aging of cotton.

Potassium fertilizer application period can alleviate the premature aging of insect-resistant cotton and help to increase cotton yield. The Agricultural University Chemical Control Research Group further discussed the operation problems of potassium fertilizer application period and application rate allocation. The results show that When the potassium application rate is 6-8 kg K2O/mu, the effect of potassium sulfate is better than that of potassium chloride. In order to overcome the problem of premature aging of cotton plants, the application period of potassium fertilizer should be divided into base fertilizer and top dressing twice, and the top dressing should be extended to Potassium application during the flowering period is appropriate. The distribution ratio of the two potash fertilizers is superior to “40% base fertilizer + 60% top dressing (full bloom period)”. The distribution characteristics of "pre-light and heavy" in the application period of potassium fertilizer are aimed at delaying the problem of premature aging, in order to make full use of the physiological functions of potassium nutrition, and to strengthen the synthesis and transportation of photosynthetic products in the late stage of insect-resistant cotton. Its rationality is screened by comparison of a large number of test results. This kind of potassium application technology is different from the previous ones. The proportion of potassium applied to the base fertilizer is obviously reduced in the potash fertilizer operation. The base fertilizer application only accounts for 40% of the potassium fertilizer, while the proportion of the fertilizer application potassium increases to 60%, and the potassium fertilizer will be applied. The period is late to the flowering period. If you look back, there are three differences between the potassium application and the high-yield cotton. The first is that the amount of potassium is generally increased. The second is that the ratio of base potassium is light and the weight of topdressing is heavy. Flowering, while the management of high-yield cotton in the past emphasizes that topdressing should be carried out during the bud period.

(Senior Consultant of Sinofert, Professor of China Agricultural University Cao Yiping)
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