Abstract

With increasing knowledge about the major and micro nutrients, and their role in the life history of a plant and crop production, fertilizer application has become a part of cultural operation in a scientific way. Eventually the economic attributes such as the height of the plant, productive tillers, nutritive straw, and the high grain yield have to be taken into account. The amount of N utilised at different growth phases of the rice plant varies from variety to variety. We have sufficient evidence to show that N supply increase in tillering, shoot growth, root development and other factors which have been amply demonstrated. N starved rice plant showed reduced shoot growth and poor tiller production. (Tanaka et al, 1964). Bhattacharya and Sircar (1963), Baba (1961), however, noticed that beyond certain limit, N no doubt increased productive tillers but decreased ripening percentage. Srinivasalu and Pawar (1963) observed a progressive increase in the shoot/root ratio corresponding to increase in N supply. The grain yield of rice naturally depends upon yield components and determinants, such as, number of panicles per plant, their length, number of spikelets, filled grain percentage and mean grain weight. Comparing japonica and indica varieties, Tanaka et al. (1958 a) observed that maximum number of filled grain was seen at 20 ppm level in indica varieties whereas in japonica varieties at 150 ppm level of N. They have also clearly indicated that for indica variety 30 to 40 kg N/ha and japonica varieties 80 to 90 kg N/ha were economic dosages.

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