Cotton

Cotton

Nutrient Management

Introduction  Nitrogen  Phosphorus  Potassium  Micro Nutrients  Hybrid Cotton Nutrient Management Zonewise Nutrient Recommendations 

Introduction Soils in cotton growing areas have a low organic matter i.e., 0.5 to 1.25%, albeit cotton shed residues like burs, leaves, flowers etc., It responses to organic matter addition. In tropics and sub-tropics addition of 10-12 tones of farm yard manure annually is preferred. Application on seed lines is advantageous. The mineral nutrition of cotton depends on both the cotton roots ability to explore the soil and on the soils ability to supply N,P & K nutrients. The physico - chemical and biological conditions around the roots and their close interaction with organic matter in the soil & also play an important role in mineral nutrient uptake by plants. Nutrients play a role in the two major yield elaboration's process i.e., Growth, which involves quantitative modifications. With an increase in size and development or differentiate which involves quantitative modifications resulting in the acquisition of new morphological or functional properties. These processes are governed by various substances whose synthesis is indirectly linked to the supply of N, P & K to the plant. In tropical India, cultivar MCU-5 yielding 3.2 t/ha seed cotton removed 190 Kg N, 61 Kg P2O5 and 195 Kg K2O. The role of major, MicroNutrients and Nutrient deficiency as well excesses symptoms are as follows:

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Nitrogen 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 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 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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Micro Nutrients Magnesium Helps to keep in balance the growth of the plant. Necessary for the development of the cell walls and strength in the plant. Calcium deficiency causes plants to have weak stems and to topple over, somewhat like an attack of seedling diseases, deficiency symptoms are hard to spot in the field. Magnesium  This is one of the most important elements in the manufacture of chlorophyll. It also helps to move starch and phosphorus about in the plants. Magnesium shortage causes cotton leaves to turn purplish red, except that their veins remain green. The bottom leaves are affected first and drop off later in the growing season. Sulphur Sulphur also assists in the synthesis of chlorophyl and in making protein. Sulphur and nitrogen deficiencies look something alike. If yellowing symptoms shown up and you thing your nitrogen supply is adequate, chances are there for the plant for lacking Sulphur. Iron Iron is often present in the soil, but generally in an unavailable form. It is used in making chlorophyll and when lacking causes chlorosis of the leaves. Boron  Cotton requires boron in relatively large amounts as compared with other plants. This element and calcium do some of the same jobs. Scientists say that it is very important to maintain the right proportion of boron and calcium in the soil. A plant deficient in boron will be dwarfed, buds will die and the young leaves will turn yellowish green. In extreme cases boron deficiency causes squares to shed. Alkaline soils are most likely to be lacking in available boron. Manganese Evidently manganese plays a big part in some of the complex nutrient processes that are necessary for plant growth. Manganese deficiency cause leaves to turn reddish grey, except that the veins remain green. Too much available manganese will cause a disease known as crinkle leaf. Zinc  The production of chlorophyll is aided by zinc. When it is lacking, the plant will develop a chlorotic or mottle-leaf condition. Alkaline soils are more likely to be lacking in available zinc. Copper Apparently this element is needed only to a limited extent in cotton to help balance plant growth. Alkaline soils are likely to be lacking in available copper. Molybdenum  This is a newcomer to the list of necessary trace elements. Scientists do not know much about it, except that when it is lacking, plants tend to turn pale. It seems to be necessary for nitrogen utilization.

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Hybrid Cotton Nutrient Management The fertilizer management of hybrid cotton enjoys a spectacular difference from that of varieties. The cotton varieties have generally poor vegetative and reproductive growth than the hybrids. The hybrids have the potentiality to bear a higher leaf area per plant much earlier to varieties and require relatively higher nutrition at early stages. Similarly, the hybrid cotton plant bears more fruiting points and has larger bolls. This also necessiates more nutrition. As the nutritional demands at various stages of growth of hybrid cotton can ultimately decide the kappas yields, a careful planning of schedule and quantity of fertilizers is needed in case of hybrid cotton. Nitrogen The hybrid cotton is reported to response upto 320 kg N/ha. But a reduction in Kappas yield, if the level of added nitrogen was increased to 300 kg N/ha. A study of growth pattern of hybrid cotton plant indicates that: A faster rise in the rate of dry matter production leads to higher total dry matter production and accumulation at early stages. Higher leaf area per plant and longer leaf area duration recorded in hybrids at early stages of growth facilitate longer and higher absorption of added nutrients. Overlapping rhythms of leaf, branch, square, flower and boll development necessiates the supply of nutrients at various stages of growth rather than single dose. Several other workers have reported about the benefits of split application of nitrogen to hybrid cotton in increasing the Kappa's yields. Low temperatures reduce the availability of nitrogen to leaves. Severe shortage of nitrogen supply to the leaves causes reddening of leaves and reduce the Kappas yield drastically. Foliar application of nitrogen at flowering and post flowering period is found to be beneficial to increase the Kappas yield. The common recommendation and practice of Nitrogen through foliar feeding is 10-15 kg/ha. Phosphorous Efficiency of nitrogen utilization increases when applied in combination with phosphorous. Generally recommended applying phosphorous as basal dose, particularly in band or spot application to avoid more contact with soil particles. Potassium Application of Potassium increases the fibre maturity, micronaire value and fiber uniformity. Reduces wilt infection. Adequate and timely application of potassium forms good fertilizer management in hybrid cotton. Hybrid cotton has the potentiality to take up as much as 122-125 kg/ha but varies widely in different situations

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Zonewise Nutrient Recommendations Region & Season Varieties/ Hybrid Total -N (Kg/ha) Split applications P2O5 K2O Split application At days (K)       30DAS 60DAS 90DAS Entire Basal 30DAS 60DAS 90DAS Coastal Kharif Varieties 90 30 30 30 45 45 15 15 15   Hybrids 120 40 40 40 60 60 20 20 20 Rabi Varieties 135 45 45 45 45 45 15 15 15   Hybrids 150 50 50 50 60 60 20 20 20 Rayala Seema Mungari Varieties 20       20           American (Rainfed) 40 20 20   20           Hybrids 120 40 40 40 60 60 20 20     American (Irrigated) 90 30 30 30 45 45 15 15 15