Effect of Seed Phosphorus and Soil Phosphorus Applications on Early Growth of Rice (Oryza sativa L.) cv. IR66
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The vigour and size of rice seedlings in the nursery are generally correlated with final grain yield. The present study examined the possibility that increasing seed phosphorus (P) concentration would stimulate early growth of rice seedlings and therefore would have the potential to increase rice yield. Rice seeds with a uniform size and three levels of P concentration (0.115, 0.173, and 0.240% on a dry weight basis) were sown in pots on a P deficient soil with three levels of P supply (0, 7.75, and 38.8 mg P kg^<-1> soil) to investigate their effect on root and shoot dry weight and P accumulation at three harvest times, 10, 20, and 30 d after sowing (DAS). The effect of seed P concentration on plant growth was greatest at a low soil P concentration and it was less pronounced with increasing soil P concentration and with time at all levels of soil P. At 10 DAS, shoot dry weight was 15% higher at a high seed P concentration (0.240%) (p<0.01) than at a low seed P concentration (0.115%) at each level of soil P supply whereas at subsequent harvests (20 and 30 DAS) the effect of seed P concentration was observed only when the soil P supply was deficient. In contrast with its effects on shoot dry weight, high seed P concentration increased root dry weight only at the latest harvest (30 DAS). The fact that high seed P increased P concentrations in shoot tips, and in roots at 10 DAS suggests that improved P nutrition of seedlings in the first 10 DAS may be the mechanism by which high seed P concentration stimulates early growth, especially in soils with low P concentration. Sowing rice seed with high P concentration may be beneficial for increasing farmer's rice yields, in P deficient soil, and requires further field investigations.