Comparative Response of Groundnut (Arachis hypogaea L.) to Three Phosphatic Fertilizers

Two field experiments were conducted with groundnut on Tolewal loamy sand soil to compare single superphosphate (SP), triple superphosphate (TSP) and diammonium phosphate (DAP) as source of P. The groundnut yield increased with applied P, but significant increase was obtained only with SP in the first year and with SP and DAP in the second year. Applied P increased the concentration of P in kernels and in foliage over control (no-P) irrespective of the fertilizer source. S content, however, increased significantly only with the application of SP. The lack of response to fertilizer phosphorus in these P and S deficient soils (0–15 cm) can be attributed to the sub-surface soil layers rich in available P, and imbalanced nutrition caused by S deficiency. To investigate whether the superiority of SP was due to its S contribution, an additional experiment was conducted in the second year, in which S (as gypsum) equal to that supplied by SP was added to TSP and DAP treatments. The pod yield and concentration of P and S in foliage were practically equal from all the three fertilizer sources.