Agriculture College, Gwalior, M. P.
A study of the effect of N, P and K fertilizers on the availability of potassium in four soil types of Madhya Pradesh showed that ammonium sulphate at the rate of 30 and 60 lb N per acre significantly decreased the availability of soil potassium in all cases. Superphosphate at 30 lb P2O5 per acre had no effect and the 60 lb dose at 15 and 30 days was not effective but the latter showed a significant decrease at 45 days. Muriate of potash at 30 and 60 lb K2O per acre, with or without a basal dose of N and P, increased the available potassium in all soils. When used in combinations, only NP and NK interactions were found significant. Nitrogen in combination decreased the available K while potash application increased it. Effect of phosphate was not consistent. It appears potash fixation is predominant up to 16 days or less after which there is little fixation or release till 30 days and thereafter a release of fixed potassium takes place resulting in an increase in available soil potassium as observed on the 45th day.
