Effect of low grade rock phosphate, single super phosphate and their mixtures on soil exchangeable calcium, Δ Ca in a groundnut-maize cropping system on the acid Alfisols of Odisha state, India over two years

Abstract

To find out the effect of low grade Udaipur rock phosphate (URP), single super phosphate and their mixtures on exchangeable soil calcium at different growth stages of a groundnut- maize cropping system, a field experiment was conducted in a randomized block design with three replications and eight treatments from 2013-14 to 2015. The soil has a loam texture, a pH of 5.18, low available nitrogen and medium phosphorus and potassium. In control, exchangeable calcium decreased gradually from the initial value of 1.31 c mol (p+) kg-1 to 0.74 c mol (p+) kg-1 after four seasons. In sole URP treatments (T2 and T7) the exchangeable calcium in T2 and T7 after four seasons were 1.07 and 1.01 c mol (p+) kg-1 respectively. The highest value of exchangeable calcium 1.18 c mol (p+) kg-1 was recorded in SSP+ lime treatment (T8) followed by 1.16 in SSP (T3) and 1.15 c mol (p+) kg-1 in URP+SSP 1:1 (T5) treatments respectively. Maximum dissolution of URP in the root zone of maize-groundnut cropping system occurred during 30-60 DAS after sowing whereas higher dissolution of URP occurred within 30 DAS in URP+SSP (1:1) treatment.