Nitrogen and Cotton Nutrition

1. Nitrogen in cotton: the average content of nitrogen in plants accounts for about 1.5% of the dry weight (range 0.3-5.0%). Cotton seeds contain 2.8-3.5% nitrogen, fiber 0.28-0.33%, and stems 1.2-1.8%, which are crops with high nitrogen content. According to the experiment, lint yield per mu is 62.7-94.7 kg, nitrogen accumulation from emergence to budding stage accounts for about 4.5% of the total accumulation in a lifetime, from budding to flowering accounts for 27.8-30.4%, from flowering to boll-opening accounts for 59.8-62.4%, and from boll-opening to harvest accounts for 2.7-7.8%. It can be seen that the period from flowering to boll-opening is the highest nitrogen accumulation of cotton. The existing forms of nitrogen in plants can be divided into two categories:

1. Non-protein nitrogen: also known as soluble nitrogen, refers to nitrogen soluble in water or certain solvents, including nitrate nitrogen, ammonium nitrogen, soluble amino acids and other soluble nitrogen compounds.

2. Protein nitrogen: macromolecular nitrogen compounds such as proteins that are insoluble in general solvents. Non-protein nitrogen and protein nitrogen in plants are constantly changing and transforming each other. In the old leaves and organs, the decomposed nitrogen is mainly decomposed, and the decomposed nitrogen is transferred to the young organs for re-synthesis; in the young organs, it is mainly synthesized. When the seed is formed, the nitrides in each organ can be decomposed and transferred to the seed to be synthesized and utilized again. Generally speaking, in the vegetative growth stage of plants, the proportion of non-protein nitrogen is higher, while in the reproductive growth stage, especially after entering the mature stage, protein nitrogen is absolutely dominant, otherwise there will be excessive growth, greedy green late maturity, disease spread and other phenomena.

Soil also contains various forms of non-protein nitrogen and protein nitrogen, the former is called hydrolyzed nitrogen, which is easily absorbed by crops, but crops often absorb a large number of nitrate nitrogen and ammonium nitrogen.

The distribution of nitrogen in plants is concentrated in the most active part of life. Therefore, the adequacy of nitrogen supply affects the growth and development of plants to a great extent. The bud and boll stage of cotton is a particularly important stage of nitrogen nutrition. At this stage, ensuring normal nitrogen nutrition can promote growth and increase yield. Nitrogen entering the crop may also be lost through the secretion of soluble nitrogen and the volatilization of ammonia, mainly at the top of the crop, especially from flowering to maturity. It is estimated that the loss of nitrogen inhaled by crops can reach 5 kg / mu every year.

In production, nitrogen deficiency is often encountered. Nitrogen deficiency is generally characterized by short and weak cotton plants, reduced branches and budding blossoms, few and small bolls, yellowish green leaves, and basal leaves gradually withered, significantly premature senescence and precocious maturity. The excessive nitrogen nutrition showed that the growth was too luxuriant, the leaf was large, the petiole was long, the leaf color was light green, the axillary buds were born constantly, the buds and bolls fell off more, the late maturity, the non-protein nitrogen in the body was too much, it was easy to be damaged by diseases and insect pests, the rotten bolls of cotton increased, the boll shell was thick, and the fiber quality decreased.

Second, the physiological function of nitrogen: nitrogen is a component of many important organic compounds in crops, such as proteins, nucleic acids, chlorophyll, enzymes, vitamins, hormones and so on. Protein nitrogen can account for 800.85% of total nitrogen in plants, and the average content of nitrogen in protein is about 16%. Nitrogen deficiency in plants results in a decrease in protein synthesis and hindrance in the formation of new cells, resulting in slow or even stagnation of plant growth. Without nitrogen, there would be no life, so nitrogen is called the element of life.

Chlorophyll is the place where plants carry out photosynthesis. when nitrogen is deficient, the content of chlorophyll in plants decreases, leaves yellowing, photosynthesis weakens, and crop yield decreases obviously.

The enzyme itself is a protein and a biocatalyst for metabolism in plants.

Third, the absorption and utilization of nitrogen by crops: crops have the ability to absorb and assimilate inorganic nitrides, and the nitrogen absorbed from the soil is mainly ammonium salt and nitrate. The ammonium nitrogen absorbed into the body can directly combine with photosynthates to form amino acids, and then form other nitrogen-containing organic compounds. The nitrate nitrogen can be absorbed and utilized only after it is reduced to ammonium nitrogen in the body. Plants directly absorb urea and some ammonium salts as nitrogen sources through leaves and roots, but the assimilation process of urea in crops is not fully understood. It is generally believed that urea is decomposed into ammonium nitrogen under the action of urease in crops.

Fourth, the relationship between cotton nutrient absorption and yield: according to the experiment, the nutrient absorption per unit area of cotton increases with the increase of yield, but not in proportion, but the nutrient uptake of every 50 kg lint production decreases with the increase of yield. nutrient utilization efficiency increases with the increase of yield, and the absorption and utilization of nitrogen is also the same rule: