Partial acidulation of phosphate rock for enhanced phosphorus availability in alluvial soils of Bihar, India

Abstract

The present study was undertaken to fractionate partially acidulated phosphate rock (PAPR) and evaluate its effect on Phosphorus availability in alluvial soils. For this purpose, low grade phosphate rock was collected from Udaipur, Rajasthan and acidulated at different degrees with sulphuric acid (H2SO4) (v/v)Results from an incubation study showed that the available fraction of P [Water soluble (WSP) and Citrate soluble (CSP)] increased with increasing degree of acidulation. The maximum WSP was obtained at 50% H2SO4 (52.30% of total P) and the maximum CSP was obtained at 80% H2SO4 (49.54% of total P). 50 % dissolution of rock phosphate was the best treatment and found to be at par with that of 60% and 80% but was significantly superior to rest of the treatments. The maximum WSP in the soil samples was obtained after acidulation with 50 %H2SO4 and the maximum Olsen’s P by the 14th day of incubation. An increasing trend was found at initial stages of incubation (7-14 days) with a notable decrease in the later stages. WSP demonstrated the maximum correlation at 40% dissolution(r = 96* for first order reaction, r =95* for second order reaction) while for Olsen’s P, the maximum correlation was found in initial rock phosphate sample (r =88* for first order reaction, r =94* for second order reaction). Kinetics analysis of the obtained rock phosphate demonstrated that the PARP has more influence on phosphorus release pattern as compared to the inorganic P (SSP).