The relationship between N, -P, - and K- efficiency and crop yield: the uptake and transport of solutes

The reason deficiency conditions affect crop yield has not been analysed critically, in relation to the major parameters which determine crop yield. This report is concerned with a study of the situation in TN-1 and IR-8 rice in relation to one aspect of the problem, namely, uptake and mobilization of inorganic and organic solutes. Although P-deficiency did not affect much the mobilization of 3H-labelled NH4+ ions in the vegetative or in the reproductive state, the panicles of K-deficient plants contained only a small amount. 59Fe and 45Ca were least distributed in the panicles and flag leaves, respectively, of deficient plants. The distribution of 32P -phosphate in the panicle and the flag leaf was curtailed almost to the same extent but 35S -sulphate was distributed less to the panicle than to the flag leaf. As compared to NPK control only 40 to 65% of U-14C - sucrose or 1-14C -valine (applied to the flag leaf) was trans-located to the panicles of deficient plant. The mechanism concerned with uptake and transport of solutes thus is adversely affected by deficiency conditions leading to poor crop yield. (author)