Comparison of NP-Complex Fertilizers with Zinc for a Maize-Green Gram Sequence

Greenhouse pot culture experiments were conducted to evaluate the direct and residual effects of ammonium polyphosphate (APP: 12-56-0), diammonium orthophosphate (DAP: 18-46-0) and nitrophosphate (20-20-0), as sources of phosphorus and carriers of zinc (Zn) for a maize-green gram sequence grown up to flowering in an Ultisol, an Entisol and a Vertisol. Direct effects on maize indicated that application of P sources significantly increased the dry matter yield, and uptake of P and Zn in all the soils. The comparative data from different Zn-P blends indicated that Zn-APP blend was significantly superior to both Zn-DAP and Zn-NP blends in a Vertisol. whereas. both Zn-APP and Zn-DAP blends were. in general, equally effective in an Ultisol and an Entisol. The residual effects of Zn-APP blends in terms of enhanced dry matter yield of shoot and P uptake compared to Zn-DAP and Zn-NP blends were observed for the second crop of green gram only in the Entisol and Vertisol, the effects in the Ultisol being equal.