Cotton topping is expensive at the right time.

Cotton has unlimited growth habits, under certain temperature conditions, the top continues to grow and elongate, and continue to differentiate into new stems, leaves and fruit branches. Topping is to knock off the top manually, so that it no longer produces new fruit branches, so that most of the cotton bolls can open bolls before frost. Therefore, this is a key task to manually regulate the growing period of cotton. Before topping, cotton plants had apical dominance, giving priority to the supply of water and nutrients, while after topping, priority was given to the organs with the fastest growth and development. Thus it can be seen that topping is related to the transport and distribution of nutrients in cotton plants, so it is an operation that has a profound impact on the physiological activities of cotton. Because the main stem no longer produces new leaves after topping, it can also be regarded as artificially terminating its vegetative growth and transforming it into reproductive growth.

When is the best time for cotton topping? As the saying goes, "when it comes to branches, time does not wait for branches." It means that it can not only be calculated according to the date, but also can not be calculated only according to the number of fruit branches, but should comprehensively consider the two factors of season and cotton plant growth status. There are generally 14-15 fruit branches in the cotton area of central and southern Hebei, and it is suitable for topping on July 15-20.

How many fruit branches are the most suitable for each plant? It depends on the density, soil fertility, cotton growth, boll setting in the middle and lower parts, and variety characteristics: (1) those with high density have lower requirements for boll setting per plant, and should leave fewer fruit branches and more fruit branches when the density is small; (2) fertile soil and strong cotton should leave more fruit branches, thin land and weak growth; (3) there are more bolls in the middle and lower parts, less fruit branches in the upper part and more bolls in the upper part. (4) there are fewer fruit branches in the upper part of the early varieties and more fruit branches in the late varieties, and (5) the boll setting potential per plant of hybrid cotton is higher, so it is better to leave more fruit branches than conventional cotton.

In terms of specific operation, if the early cotton plant reaches the desired fruit branch in the middle of July, it can start topping, and after hitting on July 20, the high-yield field and late field can be postponed for a few days. If there are too few fruit branches or bolls in special circumstances such as disasters, the topping time can be postponed to the end of the month. After topping, gibberellin and foliar fertilizer are sprayed to promote the formation of buds (see member Newsletter No. 92 for details). Topping is the best method, which can not only reduce the nutrient consumption of cotton plant, but also promote its transformation as soon as possible. After topping, we should strictly guard against pests and stop harming the buds. Cotton topping is expensive at the right time, and you must not miss the opportunity for fear of falling off. The topping of autumn peach can not be achieved in some cotton fields, and the late topping is one of the important reasons.