Why must organic fertilizer be applied continuously for sustained high cotton yields?

Although cotton is a relatively tolerant crop when it comes to poor soil, achieving high and stable yields requires cotton fields to have fairly high fertility. According to measurements by the Cotton Research Institute of the Chinese Academy of Agricultural Sciences, most cotton fields nationwide currently have insufficient fertility, and the levels of various nutrients vary widely and are very unbalanced. This is especially true in the cotton region of the Yellow River basin, where organic matter content is low, nitrogen supply is insufficient, available potassium content is declining rapidly, and the trace elements zinc and boron are also in the deficient or potentially deficient range. These have become important factors restricting the sustained and stable increase of cotton yields.

Cotton is a deep-rooted crop with a long growing period and a high demand for fertilizer. Cotton yield is closely related to soil fertility. Organic matter is one of the main material foundations of soil fertility. Within a certain range, cotton fields with high organic matter content also have high soil fertility. Therefore, the main way to build up fertility in cotton fields is to apply more organic fertilizer together with an appropriate amount of chemical fertilizer as a base fertilizer to the soil before ploughing. In this way, the application depth is greater, and after ploughing the soil and fertilizer are blended together, so the fertilizer effect is relatively steady, and nutrient release and retention times are long, which is conducive to improving the soil and building up soil fertility. Moreover, organic fertilizer contains a complete range of nutrients, which is beneficial to the growth and development of cotton, making the plants robust and enhancing their stress resistance.

Practice has proved that relying only on chemical fertilizers in cotton fields can achieve a temporary high yield in a year with favorable weather, but it is difficult to achieve sustained high yields. This is because applying chemical fertilizers year after year will gradually degrade soil properties, worsen compaction, and reduce permeability, which is also one of the important reasons why in recent years cotton diseases have occurred earlier year by year and become more severe year by year. In the key cotton regions where cotton fields are relatively concentrated, frequent crop rotation is also unrealistic. Therefore, to fundamentally solve the problems of sustained high cotton yields, diseases, and continuous cropping, organic fertilizer application is indispensable.

There are many kinds of organic fertilizer, mainly including farmyard manure, barnyard manure, compost, green manure, cake fertilizer, and human and livestock manure. Barnyard manure is a high-quality organic fertilizer whose main components are livestock and poultry manure and urine. Returning straw directly to the field is also a very good way to input organic fertilizer. One mu of cotton stalks yields 600-700 kg, and the stubble roots also amount to 250 kg; these are the main supplementary sources of organic matter for cotton fields. Organic matter can improve the physical, chemical, and biological properties of the soil, cementing soil particles into stable aggregate structure, while maintaining a certain porosity between the aggregates, improving the soil's water- and fertilizer-retaining performance, and improving aeration and temperature regulation, and it is especially necessary for improving sandy and clayey soils. Organic fertilizer is also beneficial to the reproduction of beneficial soil microorganisms, and can therefore inhibit the activity of harmful microorganisms such as pathogens. This makes the land more fertile the more it is cultivated, transforming medium- and low-yield farmland into high-yield farmland. Of course, this is not accomplished in just one or two years. However, in soil that has not received organic fertilizer for many years, results can be seen in the same year of application, because organic fertilizer itself contains certain nutrients that can be directly absorbed and used by cotton plants. Investment in cotton fields is actually investment in the land, and it is a basic long-term investment and construction.

The application amount of farmyard manure, straw, compost, and barnyard manure can be determined according to the quality of the fertilizer. Applying 1-2 thousand kg per mu is not too much, and even more should be applied to achieve high yields. If the fertilizer quality is low and the quantity is small, cake fertilizer should also be applied at 50-75 kg per mu. Nowadays, rural areas have many specialized and part-time livestock and poultry breeding households, and organic fertilizer has also become commercialized. The nearly pure livestock and poultry manure sold can be applied at 300-500 kg per mu, and it must be fermented before application, otherwise it will attract soil-dwelling pests.

China's land resources are limited. To meet the growing demand for agricultural and livestock products, land productivity must be continuously raised. Therefore, applying organic fertilizer not only has important practical significance but also far-reaching strategic significance.

Right now is a great time for autumn ploughing of cotton fields and application of base fertilizer. This year winter is arriving late, so the ploughing period will be extended. Those who complain that their cotton fields have poor soil and poor fertility, those troubled by low and unstable cotton yields, and those plagued by cotton diseases should act immediately and start with applying organic fertilizer to change the land conditions on which they depend for survival. They will certainly receive generous returns this year and in the future.