Phosphorus dynamics and phosphorus efficiency indices of maize and cotton in a phosphorus deficient soil

A pot culture experiment was conducted with maize and cotton to study phosphorus (P) dynamics in soil and phosphorus efficiency indices in a P deficient soil (7.2 kg ha-1) with four levels of phosphorus (0, 3.75, 7.50 and 15.0 mg P kg -1 soil). The experiment was conducted for duration of 60 days. Phosphorus -32 was used for studying the variation in isotopically exchangeable phosphorus in soil and specific radioactivity in plant. Phosphorus stress increased the root – shoot ratio in both cotton and maize and cotton recorded the higher root – shoot ratio. Rhizosphere pH after 60 days of growth was slightly acidic irrespective of the crop and available P status of maize in rhizosphere soil was higher compared to cotton. Enhanced activity of acid phosphatase was observed in cotton. At all levels of P application maize recorded significantly lesser values of Fe-P and Ca-P and higher values of saloid - P when compared to cotton. Phosphorus translocation efficiency was also higher with maize than cotton under P deficient condition (P0). Under P deficiency condition maize recorded lower Phosphorus Stress Factor (PSF) values (42.56% at P0, 22.56% at P 3.75 and 2.47% at P 7.5) when compared to cotton. Maize recorded the Phosphorus Acquisition Efficiency (PAE) of 59 per cent while in the case of cotton it was 48 per cent. Maize having depicting high PAE, PE and low PSF values is better choice for P deficient condition.