A quantitative evaluation of the comparative value of six fertilizer–nitrogen sources for potatoes

Abstract

Six fertilizer-nitrogen sources, each at three levels, together with a control of no fertilizer-nitrogen were compared in field trials in two consecutive crop seasons on a sandy soil comparatively deficient in nitrogen at Patna, Bihar. Four mathematical models were fitted to the potato yield data in order to evaluate the relative availability indices of the individual fertilizers. Data collected on final stand and 'emergence rate' index (Bartlett) showed that while urea applications gave rise to a comparatively low speed of emergence, with observed shoot injuries, nitrate of soda caused poor final stands. The other fertilizers had no effect on either the final stand or the speed of emergence.Sulphate of ammonia was chosen as the standard fertilizer for the present study. Ammonium sulphate nitrate was as good as or even slightly better, while ammonium chloride and calcium ammonium nitrate were of intermediate efficiency, in that order. Urea and nitrate of soda were decidedly poor as nitrogen sources for potatoes under the conditions of the study. The concurrent Mitscherlich curves model was found to represent the behaviour of these fertilizers with a good measure of fit.The performance of the six fertilizers is discussed in the light of the availability of NH 4 + and NO 3~, the phytotoxicity of urea and nitrate of soda, and the harmful effects of Cl~. It is concluded that ammonium sulphate nitrate is the best carrier of nitrogen among those studied for potatoes under the conditions set forth.