Comparison of methods to evaluate k availability in rice soils

Abstract

tions have been used to evaluate K availability from 29 rice soils. Of the methodsy boiling IN HNO^ extracted the highest amount of available K. The methods may be arranged as boiling IN HNO2 > hot 1.4N H^SO > IN Na^SO. (pH 1) > modified IN NaCl (pH 1) > 0.7N HCl > 0.5N HCl > Morgan’s reagent > 0.5M NaHCO^ (pH 8.5) > IN NaCl > IN NH^OAa > Water according to their relative efficiency. Extractants having acidic character were found to he superior over other methods. pH fluctuations possibly accentuated K release from the soils. All the methods correlated significantly with 60 days plant K. Highly significant correlation at 0.1% level was revealed by boiling 1 N HNO^j hot 1.4N H^SO^, IN NaCl (pH 1) and 0.5M NaHCO. (pH 8.5) with plant K. Only IN NaCl (pH 1) extractable K showed significant correlation with 90 days plant K.