To find out the effect of low grade Udaipur rock phosphate on yield and nutrient dynamic in groundnut- maize cropping system, a field experiment was conducted in a randomized block design with three replications and eight treatments consisting of Udaipur rock phosphate (URP), single super phosphate (SSP) alone or in combinations with different ratios including phosphorus control from 2013-14 to 2015. The soil has a loam texture, a pH of 5.18, low available nitrogen and medium phosphorus and potassium. The highest maize equivalent yield of 6293 kg ha-1 and relative agronomic efficiency (RAE) of 159% was recorded in SSP+ lime (0.2LR) treatment followed by URP+SSP (1:1). Combined application of SSP+ lime recorded higher P, Ca, Mg and S uptake by groundnut-maize cropping system. When the crops received URP+SSP mixture in 1:1 ratio, the RAE values were increased above the standard SSP treatment (T3) being 102% for groundnut, 105% for maize and 103% for groundnut-maize cropping system. The yield in URP+SSP mixture (1:1) was higher than for the SSP treatment, but the difference was not statistically significant (P > 0.05). Thus, combined application of URP+SSP mixture (1:1) can safely be recommended in acid soils for short duration crops like maize and groundnut as against the more costly water soluble SSP fertilizer.
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
