Abstract

A hydroponic experiment was conducted to study the effect of increasing levels of N on the yield and plant composition and critical levels of nitrogen in the straw for maximum grain and straw yield for the rice variety. Ratna. There was a sharp increase in nitrogen concentration and uptake upto 100 ppm.N.and thereafter it was gradual Up to 40 ppm the concentration of N in the grain was more than that of the straw and vice versa at still higher levels. N was more concentrated at higher levels in the straw than in the grain. The concentration of plant nutrients like P. K. Mg and Fe as well as uptake increased from 40 to 60 ppm N and remained more or less constant at still higher levels. These nutrients are highly essential for the better utilization of absorbed nitrogen whereas Sio, and Ca concentration and uptake decreased progressively with N uptake. The lodging of rice plants observed at higher levels of nitrogen might be due to the decreased concentra- tion of these elements in the plants.

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