Introduction Of the several inputs essential for crop production, the importance of fertilizers is perhaps next only to water, Maize responds well to fertilizers. Widespread deficiency of N, P, K and micronutrients like zinc, iron and copper, show the need to apply them for getting optimum yield of maize. A crop producing 62.7 quintals grain yield per hectare is estimated to consume 168 Kg N, 57 Kg P205, 135 Kg K20 and 30 Kg Zn. These nutrients are to be replenished through balanced fertilizer application and integrated use of nutrients. These principles are not new to crop production but assumes significant importance in view of steep hike in fertilizer prices and abolition of subsidies. With the development of scientific farming, commercial and food crops are used in rotation with maize instead of green manure crops thus reducing chance of natural soil recuperation. By normal cultivation practices followed by a farmer, all the essential nutrients other than N,P,K and Zn are replenished and maintained. Hence there is need to get acquainted with N,P,K and Zn nutrition and their management as they are not replenished in sufficient quantities to produce optimum corn yields.

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Organic Manures Maize crop requires a regulated and assured supply of nutrients particularly nitrogen throughout its growing period right from seedling stage to grain filling stage. A judicious application of organic manure such as well rotten compost or FYM at the rate of 15-20 t/ha about 20 days before sowing the crop, green manuring or application of oil cakes at the rate of 6-10 q/ha has been found to be most ideal for an increased crop yields, especially for a grain crop.

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Nitrogen Maize plants throughout the season take up nitrogen. Uptake is relatively slow during the first month. During the second month it becomes very rapid, if nitrogen is available in the soil. Then the uptake slows somewhat, but remains fairly rapid until near maturity. Before grain forms, leaves contain a large proportion of the nitrogen in plant. After grain begins to form, much nitrogen is translocated to grain from other parts of plant. At maturity about two thirds of the total nitrogen in the above ground parts of the plant should be in grain, with about one third in rest of the plant. As nitrogen is needed throughout crop growth and liable for leaching, split application of nitrogen is recommended. The nitrogen deficiency at any stage of the growth especially at tasseling and silking stage will leads to virtual crop failure. Deficiency symptoms V-shaped yellowing In young plants, N deficiency causes the whole plant to be pale, yellowish green and have spindly stalks. yellowing begins on the older, lower leaves and progress up the plant. V- shaped yellowing on the tips of the leaves appear later. Dosage 80 kg/ha for rainfed kharif crop. 100 to 120 kg/ha for irrigated rabi crop. Time of application 1/2 of nitrogen at sowing. 1/4 of nitrogen at knee height stage ( 35-40 DAS). 1/4 of nitrogen at tasseling stage.

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Phosphorus Like nitrogen, phosphorus is taken up by maize throughout the season. It is slow up to first month, later rapid, till the crop reaches maturity. After grain formation begins much phosphorus is translocated to grain from other plant parts. At maturity about three fourths of the total phosphorus in the above ground parts of the plant should be in grain. As the element availability, absorption and utilization is slow and being less prone to leaching, all phosphorus is applied at the time of sowing as basal dose. Deficiency symptoms Usually identified on young plants. Plants are dark green with reddish purple tips and leaf margins. Phosphorus deficient plants are smaller, grow more slowly and remain shorter throughout the growing season. Dosage 40 kg/ha for rainfed crop 60 kg/ha for irrigated crop Time of application Basal placement of phosphate in rows about 5-8 cm deep along seed rows in soil gives the best results as it is less mobile and it does not get lost through leaching.

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Potassium The potassium uptake is rapid and most of the uptake is completed before grain formation begins. Relatively little potassium is translocated from other plant parts to grain. At maturity the grain should contain not more than one third of the total potassium that is in the above ground parts of the plant. Deficiency symptoms Shorting of internodes Shortening of internodes. Yellowing of leaves and firing at the margins of lower leaves. If the deficiency is severe, lower leaves turn yellow but the upper leaves remain green. Dosage There is sufficient amount of available potassium in the soils of maize belt, hence its application should be based on soil test, however, and the crop may be fertilized with 40- 60kg/ha K20 for a remunerative return. Time of application As there is negligible amount of leaching and most of uptake is completed early, entire potassium is to be applied as basal dose along with phosphorus at the time of sowing.

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Zinc Cultivation of new plant types, leveling of fields and light texture of the soil leads to zinc deficiency thus results in poor grain yields. Zinc deficiency symptoms described as 'White bud' in maize. Symptoms of deficiency Appears rather early and plants become severely stunted owing to the restricted growth of inter nodes and leaf lamina. Deficient plants show a broad band of bleached tissues on each side of the leaf midrib, beginning from the base. Correction measures Basal application of zinc sulphate at 15-20 kg/ha after every three maize harvests becomes essential. The deficiency of zinc in plants at later stages of growth , however, may be corrected by foliar application of 5% ZnSO4 dissolved in water with half the quantity of lime ( 5% of ZnSO4 + 2.5% of hydrated lime).

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