Nitrogen Nitrogen Does Promotes the development of the green color in plants called chlorophyll and causes rapid, healthy growth. Too much nitrogen without enough of the other elements, however, can cause the plant to produce big stems and leaves and cut down on the production of cotton. It makes the plants weak and less able to resist attacks by insects and diseases or withstand wind and cold weather. Yield reduction was proportional to the length of the period during which the plant was subjected to N deficiency. Height of plant at 6 weeks and yield were positively correlated with NO3 content of leaf of 7 days old seedlings. Later stage-reduced supply of N is desirable for uniform maturation NO3 concentration. In petiole at beginning of flowering (1600 ppm), peak flowering (8000 ppm) end of flowering (2000 ppm)-fall below these levels reduce the yield. By application of N (under N deficiency) earliness of crop increases. N application (where N deficiency is observed) increased flowers three fold and bolls four folds. Combination of higher N level, frequent irrigation, high temperature results in excessive growth - fewer bolls than normal. Protein levels of seed increased. Reduced oil % but increased oil yield per unit area. Slightly longer fibers. Deficiency symptoms Leaves turn yellowish green and eventually dry up and fall off. Cotton plants begin to look sick. Cotton can stand a lot more dry weather if they have a good supply of nitrogen. Limits the development of vegetative branches. N deficiency reduces the number of fruiting branches reduction in number of flowers. Reduce amount of fruiting. Number of seeds/boll increased Slightly decreased the lint seed ratio Excess nitrogen causes High pest, disease incidence. Lodging on excess N application. Lodging leads to regrowth increased boll rot.

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Phosphorus Phosphorus Does Phosphorus is found in every part of the plant. Its most important use is in cell division, which is the basis of growth. Essential for growth of the aerial parts of the plant For better root development It is also important in the development of the seed and lint and hastens maturity For protein synthesis Increase earlyness of crop (under deficient conditions if P is applied) Increased the No of early flowers by 30-40%. More matured bolls at the first picking (50%) Cotton requires less phosphorus than either nitrogen or potassium to produce its stalk and fruit. Deficiency Symptoms Stunted growth may be the only evidence of a deficiency and can easily be overlooked or erroneously attributed to other factors. In the presence of adequate N, the leaves of some P deficient plants may become dark green or bluish green and show tints of bronze or purple along the margins. Seedlings grow slowly and maturity is delayed. A deficiency of P in plants usually does not produce striking visual symptoms. Phosphorus deficiency is often hard to spot in the field, unless the plants are alongside others that have received enough phosphorus. This is one reason for having a soil test made as a basis for deciding how much fertilizer to use. Although a soil may contain plenty of phosphorus, it can all be tied up in unavailable forms so that the plants are actually starved for phosphorus. Excess Phosphorus causes Excess phosphorous leads to more growth in lateral roots and fibrous rootlets Leads to trace element deficiencies particularly Iron and Zinc.

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Potassium Potassium does Too much nitrogen may cause the plant to grow too fast and form too much vegetation. Potassium helps in preventing this. Develops toughness in the plant - ability to resist diseases and insects and to withstand cold, wind and other adverse weather conditions. Deficiency Symptoms Potassium deficiency is known as cotton rust. First, the leaves turn yellowish green brown necrotic spots appear between veins. Yellow spots appear between the veins and eventually turn black. The edges of the leaves die and become black. Finally, the whole leaf dies and falls off. In very bad cases the whole field may shed all its leaves. Without leaves the manufacture of plant food is stopped and bolls open before they are mature. This cuts down on the yield and produces weaker and shorter fibers.

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