Detailed Explanation of Key Cotton Field Management Points in July

July is the month when cotton grows fastest and has the greatest growth volume; it is also a month of drastic weather changes, frequent disasters, and severe outbreaks of pests and diseases. Most cotton fields enter the flowering stage in early July, and by the end of July, 90% of the cotton plant's vegetative organs and reproductive organs have already grown out; the cotton root network is also established in July, forming the peak of absorption of mineral nutrients and water. Mid-July enters the dog days, which is the month when cotton transforms fastest and to the greatest extent. From the above aspects, cotton management in July has the nature of a decisive battle.

(1) Digging furrows and earthing up. It is conducive to watering and drainage, can prevent both drought and waterlogging, and also facilitates ventilation in the lower part of the cotton field, reduces humidity, increases the temperature difference between day and night, helps improve the microclimate of the cotton field, and plays a role in preventing boll rot and lodging and in promoting and protecting roots. After the plastic film is removed from the cotton field, in combination with intertillage and loosening the soil, furrow digging and earthing up should be carried out wherever conditions permit, mainly by machine and animal power, with manual assistance. Where there is a basis for intertillage, it can be completed in one operation or in two operations. Low-lying plots should have their drainage ditch systems dredged properly.

(2) Pruning and topping. The purpose of cotton pruning is, first, to regulate nutrient distribution, and second, to improve the population structure, ultimately achieving full use of resources such as water, fertilizer, light, air, and heat to achieve high cotton yields. Do not go to extremes in the use of vegetative branches (referred to as leaf branches), either leaving none at all or removing none at all. In cotton fields with relatively high density and no missing plants, basically no leaf branches should be left, but in sparse areas, areas with missing plants, and at the ends and edges of the field, leaving 1-2 strong leaf branches per plant can increase the number of bolls per plant; retaining all leaf branches is not advisable, and leaf branches that have not yet produced fruiting branches and have very small buds must be resolutely removed in early July; for those with relatively strong leaf branches that have already grown fruiting branches, the leaf branches can immediately be pinched at the tip and must no longer be allowed to grow freely. If there are too many pre-dog-days bolls, it will bring many disadvantages to the cotton plant such as premature senescence, stiff bolls, and rotten bolls, so in early July all flowers that have already opened should be removed, so that the cotton plant can save nutrients and set more bolls when conditions are suitable. In cotton fields in south-central Hebei and northwest Shandong with 2500-3000 plants per mu, according to soil fertility and density, leave 13-14 fruiting branches per plant and top in time, and it is essential to achieve autumn bolls covering the top. Do not repeatedly delay topping and blindly leave more out of fear of shedding and greed for more

fruiting branches. When planting varieties with relatively high boll weight, seek both a relatively high number of bolls per mu and a relatively high single boll weight. Do not seek, or seek fewer, early bolls and late bolls, which will greatly improve the uniformity of cotton bolls.

(3) Grasp chemical regulation firmly. This year, many areas in the north have had drought and little rain, and many cotton farmers have not dared to carry out chemical regulation. Some cotton fields have not yet carried out the first chemical regulation to this day, and most have the problems of chemical regulation being too late and the dosage being too small. Because temperatures in May and June this year were relatively high, this caused problems to varying degrees of excessive vegetative growth and weak reproductive growth, and of aboveground plant parts being relatively large while the root system was relatively small. In the earlier period, some cotton fields once showed wilting of cotton plants after sunny days. Upon inspection, some were neither disease nor fertilizer damage, but mainly caused by rapid aboveground growth, relatively large plants, high transpiration under high temperatures, and weak roots unable to supply enough water uptake. In applying the principle of using mepiquat chloride by "looking at the sky, looking at the soil, and looking at the seedling condition," the main emphasis should be on "looking at the seedling condition." As long as the cotton seedlings grow at a normal rate, chemical regulation should be carried out on time; this is called "active chemical regulation." If chemical regulation is carried out only after excessive growth, then it is "passive chemical regulation." According to the earlier chemical regulation situation and the current cotton growth condition, generally in July chemical regulation should be carried out 2-3 times: the first time at the initial flowering stage, using 1-1.5 grams of mepiquat chloride per mu; the second time at the full flowering stage, using 1-2 grams per mu; and the third time after topping, using 3-5 grams per mu. Because the cotton plants are now relatively large, during chemical regulation 20-25 kg of water per mu should be used to spray the whole plant, wetting the terminal bud and the tips of the middle and upper fruiting branches.

(4) Timely fertilizer supply. The issue of cotton fertilization is the most complex issue in cotton management. It is by no means true that the more fertilizer applied, the higher the yield; sometimes improper fertilization can even lead to the opposite result. According to analysis of the nutrient elements that make up the cotton plant, a yield of more than 600 jin of seed cotton per mu does not require a very large amount of nutrients, and there is a certain proportional relationship among the nutrient elements. For example, if a certain element is excessive, it not only causes waste, but may also affect the absorption and utilization of other elements, so fertilization values balance, reasonableness, and scientific soundness. On the basis of applying enough base fertilizer, cotton generally does not need topdressing with quick-acting nitrogen fertilizer before flowering and boll setting, so as to avoid excessive vegetative mass or excessive vegetative growth; topdressing should preferably be applied at the full flowering stage (when the 4th fruiting branch flowers), applying 10-15 kg of urea per mu depending on soil fertility and cotton growth condition; where potassium fertilizer was not applied as base fertilizer, or the amount of potassium fertilizer was too small, it should be topdressed as early as possible. For cotton field topdressing in July, apply it in the middle of the wide rows so that the cotton plants on both sides can absorb and utilize it. Never drill-apply it in the narrow rows, so as to avoid injuring the already weakened root system again. Every year there are cases of wilting caused by fertilizing too close to the cotton plants. For small seedlings that are delayed in development due to damage by herbicides or diseases, use 1% urea water to punch holes and irrigate the plants; if they still do not grow, spray gibberellin. For cotton fields with too weak vegetative growth due to drought or excessive phosphorus application, spray urea solution so that the terminal bud and fruiting branch tips extend as quickly as possible. After cotton topping, nutrients are preferentially supplied to young bolls, and the upper fruiting branches are in the state most prone to fertilizer deficiency. At this time, topdressing is not only difficult, but also constrained by drought and dry soil, so foliar spraying of fertilizer should be used to ensure the nutrients needed by the cotton plant. Foliar spraying of fertilizer not only saves fertilizer, but also has a quick effect. Because most cotton farmers year after year attach importance to the input of diammonium and compound fertilizer, relatively speaking, the degree of deficiency of available phosphorus in the soil is not too serious, and cotton's demand for phosphorus is relatively small, so foliar spraying of fertilizer should focus mainly on nitrogen and potassium. Urea and potassium sulfate are the best choices: first, their nutrient element content is high; second, their cost is low; third, they are safe to use. The spraying concentration is 2%, using more than 1 jin of fertilizer per mu each time, avoiding spraying at noon, and the backs of the cotton leaves must be sprayed wet. After topping, spray immediately, once every 8-10 days, nitrogen first and then potassium, and spraying can continue until August 10-15. The principle of cotton topdressing is not to apply excessively before flowering and not to let fertilizer deficiency occur after flowering. Once fertilizer deficiency occurs, it is very difficult to achieve autumn bolls covering the top. Applying sufficient quick-acting potassium fertilizer twice in the later stage is very important for setting more bolls and larger bolls on the upper part and for producing good lint. Potassium is indispensable for cotton fiber development, so applying potassium can increase lint percentage. In years with heavy rainfall during the dog days, especially in cotton fields that have once accumulated water, spraying potassium is even more necessary.