Changes of soil potassium as affected by different rice (Oryza sativa L.) genotypes growth

The differences of uptake and utilization of soil K by two lowland rice genotypes differed in low-K tolerance and were studied by rhizobox cultivation. The results showed that the depletion ratios of all soil K fractions in the rhizosphere of 81,394, a genotype sensitive to low-K stress, were more serious than those of Fujiandao when K was sufficiently supplied. Under low-K stress, the depletion ratio of the available K in the rhizosphere (< 2mm) of Fujiandao was 91.3 %, while it was 82.6 % in that of 81,394. The depletion ratio of this K fraction in the soil 10mm far from root surface for Fujiandao was still as high as 83. 0 %, but it decreased to 53% for 81,394. There were no significant differences between the depletion of readily- released K of two genotypes. The average depletion ratio of slowly-released K in the rhizosphere (< 3mm) of Fujiandao was 56.6%, which was significantly higher than that of 8,139,441.7%. More visible descending of soil pH in the rhizosphere of Fujiandao was found compared to that of 81,394, which might be the result of the more proton secretion adapting to low-K stress, and the reason of stronger transformation of slowly-released K into available K for Fujiandao than 81,394.