Yield and phosphorus-uptake by crops as influenced by chemical fertilizer and integrated use of industrial by-products
Syed Manzar-ul-Alam, Syed Azam Shah, Sikander Ali and M. Mohsin Iqbal
pp. 9 - 16
Abstract
To determine the best combination of P fertilizer for obtaining higher P fertilizer efficiency, industrial by-products i.e. filter cake (FC), poultry waste (PW) and di-calcium phosphates (DCP) were integrated in different proportions so as to supply 75 mg P kg-1 soil and evaluated against mineral P fertilizer i.e. single super phosphate (SSP) for growing maize and wheat in pots. The organic and inorganic fertilizers were thoroughly mixed with soil before sowing of maize and wheat while the effect of residual P on the yield and P-uptake on the following crop was assessed by growing rice in the same pots. Maize was harvested after 40 days of growth while wheat and rice were harvested at maturity. The results showed that irrespective to the source or combination, application of P increased the dry matter yield (DMY) of maize over control. Integration of PW and DCP in 2:1 P ratio gave maximum DMY and the highest P-uptake. Integrated use of FC, PW and DCP in 1:1:1 P ratio produced 95% of the maximum dry matter yield and 93% of the maximum P-uptake. Application of P through chemical source (SSP) produced 79 and 61% of maximum DMY and Puptake, respectively and resulted in lowest P fertilizer efficiency (PFE) compared to all other combinations. For wheat integrated use of waste in all tested combinations except (FC+DCP) significantly increased total P-uptake and the grain yield of wheat over SSP. Highest grain yield as well as maximum P-uptake were recorded for DCP+PW combination. However, PW+DCP and FC+PW+DCP combinations also produced grain yields equivalent to DCP+PW combination. Integrated use of wastes increased wheat grain yield ranging from 15-42% and the PFE from 9-65% over SSP, respectively. Assessment of the residual P effect showed that integrated use of fertilizers resulted in 5-30% more grain yield than SSP alone. Thus for improved P fertilizer efficiency and sustainable crop yields, integrated use of PW and DCP in 2:1 P ratio was the best combination.
