Abstract

Indian soils are known to be dificient particularly in N, but believed to contain large reserves of P and K. This belief was based on the resuls of numerous trials conducted at the Research Stations where negligible responses to phosphate and potash applications were obtained. The Research Stations, however, are likely to be not quite representative of the tract not merely because of their small number but because of the continued manuring and better managerial practices over a number of years which is not a feature of an average cultivator's field. The need for trials on cultivators' fields has been increasingly felt on the recognition that recommendations based on the results of such trials alone could be reliably passed on for adoption by cultivators in a given tract. A series of simple fertilizer trials were therefore, laid out in cultivators' fields since 1951. From the results of trials conducted during 1958-59 to 1961-62, it was observed that not much- difference in responses existed to the different sources of N viz., Ammonium sulphate, Ammonium su phate nitrate, Urea and Calcium ammonium nitrate) It was also seen that economic response to phosphate and potash existed in many selected pockets all over the country. Accordingly, the programme of trials was revised with effect from 1962-63 in order to study more critically the response curves of N, P and K alone and in combination and response surfaces of two or more nutrients..

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