FERTILIZER MANAGEMENT IN VEGETABLE CROPS

Fertilizer management is an important aspect of vegetable production. A good fertilizer management can give a manifold increase in the yield of vegetables. There are three factors which constitute the principles of commercial fertilizer practice – i) Which commercial fertilizer to be used ii) When it should be used iii) How it should be used A. Which commercial Fertilizer and how much to be used - The selection of a suitable fertilizer and its quantity depends largely on the – a) Essential element level of the soil with respect to the content of the fertilizer b) Essential element requirement by the crop c) Season of the year d) Spacing e) Irrigation facility a) Different types of soils vary in their relative supply of essential elements. - Thus for the same crop grown under practically the same temperature level and under favorable supply of water and light, each soil may require fertilizer in different ratio. - Moreover, soil reaction may also influence nutrient requirement by the vegetable crop. - Soils for such crops must contain large amounts of bulk nutrients e.g., NPK, besides moderate amount of micronutrients in available form.

- When the soil pH is below 6.5, phosphorus, magnesium and calcium are not available for most of the crops. - Similarly when pH is above 7.0, iron, manganese, boron and zinc become unavailable b) Different crops grown on the same soil also differ in fertilizer requirements – I. In general leaf vegetables are considered to be typical nitrogen crops. - Nevertheless it should be realized that crops like cabbage and lettuce remove more potash than nitrogen from the soil which should, therefore, be well provided with phosphate and potash. II. Fruit bearing vegetables differ in the requirement of fertilizers from crop to crop. - But most of them need a balanced ratio of nitrogen and potash, whereas a liberal application of phosphorus is essential. III. In case of vegetables grown for their roots, tuber and bulb crops require more attention for a liberal application of potash, while a moderate application of nitrogen may be recommended. However, a desirable ratio of NPK under average condition may be recommended as follows – N : P : K Leaf vegetable ------ 1 : 1 : 1 Fruit vegetable ------ 1 : 2 : 1 Root vegetable ------ 1 : 2 : 2

c) Principal factors concerned are temperature and rainfall. - Low temperature reduces the growth of favorable soil microorganisms and, therefore, require artificial application of nitrogenous fertilizer. - On the other hand high temperature enhances such growth and thus permitting less requirement of such fertilizer. - Similar effects of rainfall may also be accounted for, high rainfall favors leaching out of N2 indicating liberal application of nitrogen. d) Plant spacing influence in determining the fertilizer requirement. - Wider spacing indicates limited application while closer ones suggest liberal application. e) Liberal application of fertilizers may be recommended for the vegetable crops having irrigation. - But this may be restricted to those are growing without irrigation.

B. When to Use Fertilizer in Vegetables ? - This means time of application of fertilizer. - It is well known that nitrate ions leach readily, whereas phosphorus and potassium ions do not. - Therefore, nitrogen may be most effectively used when applied just prior to maximum uptake by the vegetable plants. - However, if a heavy rate of nitrogen fertilization is planned, 1/2 or 2/3 of the quantity may be applied at the time of planting and the rest of it may be applied at the time of maximum growth.

C. How to apply Fertilizer in Vegetables? - This means the method of fertilizer application in vegetables. Different methods of fertilizer application are may be outlined as follows. a. Basal application i) Broadcasting : In this method fertilizers are broadcasted before sowing and ploughed in or harrowed in after ploughing before final land preparation. ii) Band placement : Applied in furrows 10 – 15cm to one or both the sides of the row and a little below seed level. iii) Basal placement or plough sole placement : Fertilizers are thoroughly mixed with the soil in the row below the seed.

b. Top dressing i) Broadcasting : Broadcasting fertilizers on standing crops in one or two installments. ii) Side dressing : Applied on one or both the sides 10 – 15cm apart in band on standing crops once or more times. iii) Ring placement : Applied in ring form around growing plants 10 – 15cm apart on standing crops once or more times. iv) Liquid application : In the liquid method soluble fertilizer is applied in solution with water. - Three distinct methods are in use : By direct application to the soil, By a foliage spray, and with irrigation water.