First, the nutrients needed for cotton
Cotton needs many nutrients, and there are 16 known ones, namely carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, zinc, manganese, copper, molybdenum, boron, and chlorine. Hydrogen and oxygen accounts for about 95% of the dry weight of the plant, mainly from air and water; other various elements together account for about 5% of the dry weight of the cotton plant, mainly from the mineral salts of the soil. At present, cotton fields are mainly deficient in nitrogen, phosphorus and potassium.
Second, common deficiency symptoms
When the supply of nitrogen is insufficient, the cotton plants grow slowly, the plants are dwarf, the leaves are small and the leaves are light, the number of fruit branches and the total number of fruit segments is small, the bells are shed more, aging is earlier, the bells are less and light, and the yield is low.
When the supply of phosphorus is insufficient, the cotton plants grow slowly, the roots grow poorly, the leaves are dark green, the plants are short, the reproductive growth is hindered, the bolls and maturation period are delayed, the bolls light seeds are small, the infertile seeds increase, and the fiber maturity is poor. And quality has dropped.
When the supply of potash is insufficient, in the seedling or bud stage, the leaves of the middle of the main stem first appear chlorosis, and then turn yellow. Afterwards, the tips and edges of the cotton are scorched and curled downward, and finally the entire leaf becomes red-brown; when the leaves are serious, Dry off, usually referred to as "red stem blight." The cotton fields suffering from this disease often exhibited premature aging of cotton plants, small bolls, poor boll opening, poor fiber maturity, and low cotton yield.
Insufficient supply of boron, petiole ring zone, cotton buds often necrosis, the plants grow dwarf and more branches, severe cotton plants appear to not flower, no bell, or buds without flowers, flowers but not real.
When the supply of zinc is insufficient, the cotton leaves are small, and there is a lack of green between veins, resulting in necrosis of the leaf tissue, and the lack of green part becomes bronze.
When the supply of manganese is insufficient, the leaves become cup-shaped, chlorosis between leaves and veins, shortening between severe seasons, and dwarfing the plants.
In addition to nitrogen, phosphorus, and potassium, the lack of symptoms of other nutrient elements is generally not very obvious. Therefore, the application of nutrient elements is mainly determined by the content of the soil.
III. Effect of NPK Fertilizer on Growth and Development
Nitrogen has the most obvious effect on cotton, and from the beginning of the seedling until flowering and ringing, it needs a proper amount of nitrogen supply. The nitrogen supply is appropriate, and the cotton leaves are dark green, robust, with many bells, high yield, and good quality. If the initial supply of nitrogen is too much, it will cause cotton to grow long. If there is insufficient supply in the middle of the reproductive period, the cotton leaves will turn yellow and become smaller, fall off more, and later premature aging, low yield; if the supply is excessive in the middle and late period, it will cause the cotton to grow wild, and reduce the production in the late stage. Reduce quality. Phosphorus can promote the development of plant roots in the early period of cotton growth, so that strong seedlings early on, have an important role in promoting the early flowering bud early blossom; in the late growth stage can promote the boll mature, increase the boll weight. Potassium plays a role in strengthening the stalks and enhancing the resistance to undesirable factors; in the absence of potassium, the plants are susceptible to disease, the leaves turn red, and leave early. Cotton stem blight is mainly caused by potassium deficiency.
Fourth, the need for fertilizer characteristics of cotton
Nitrogen absorption accounted for 5%, phosphorus accounted for 3%, and potassium accounted for 2% at the seedling stage; 11% of nitrogen absorption, 7% of phosphorus, and 9% of potassium accounted for at the beginning of flowering stage; and 55% of nitrogen was absorbed from flowering to flowering stage. Phosphorus accounted for 24% and potassium accounted for 36%; nitrogen absorption accounted for 23%, phosphorus accounted for 52% and potassium accounted for 42% from flowering to boll-opening stage; nitrogen uptake was 5% from boll-pumping to picking cotton, 14% from phosphorus, and 11% from potassium . From the above, we can see that the overall trend of fertilizer demand during the whole growth period of cotton shows a dynamic pattern of “less, more, lessâ€. The absorption at the seedling stage is less, and the absorption after emergence is significantly increased, reaching the peak of absorption at the flowering stage, entering the period of opening of the boll opening, and weakening the absorption capacity of the roots, thus rapidly reducing the absorption. The absorption characteristics of N, P and K in different growth stages of cotton are also different. The absorption peak of N fertilizer is at the front (from flowering stage to flowering stage), and the absorption of P and K fertilizer is at the later stage (from flowering stage to boll opening stage), which is beneficial to the application of phosphorus and potassium nutrition. Ring the bell to promote precociousness.
Fifth, the principle of fertilization
According to research, for every 50 kg of lint produced, cotton absorbs approximately 13.35 kg of nitrogen, 4.65 kg of phosphorus, and 13.35 kg of potassium from the soil. The ratio of nitrogen, phosphorus and potassium is 1:0.3:1. However, with the increase in yield, there is a trend to reduce the amount of fertilizer, so the increase in cotton production is not simply a result of fertilizer, but rather the combined effects of various cultivation techniques. The principle of fertilization for cotton should be based on basal fertilizer and supplemented by topdressing; mainly organic fertilizers and chemical fertilizers should be supplemented. The traditional fertilization technology is based on the application of basic fertilizer, according to the characteristics of the needs of fertilizer in different growth stages of cotton, to master the principle of "light planting fertilizer, stable application of bud fertilizer, reapplying flower bell fertilizer, top dressing top dressing fertilizer" principle, simplify the fertilization technology Then save Miao Fei, bud fertilizer and cap fertilizer, fertilization measures to "apply enough base fertilizer, reapply flower bell fertilizer."
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