Residual Efficiency of Diammonium Orthophosphate and Ammonium Polyphosphate to Maize Crop in Wheat-Maize-Maize Cropping Sequence on a Typic Ustochrept Varying in Available Phosporus

摘要

Direct and residual efficiency of diammonium orthophosphate (DAP) and ammonium polyphosphate (APP) was evaluated in a green house experiment conducted on a Typic Ystochrept having 3.0, 6.4, 10.0, 14.8 and 22.0 mg available P kg~1 (0.5 N NaHCO_3 extractable) with wheat-maize-maize cropping sequence. The fertilizers were applied to wheat crop at 20, 40 and 60 mg P kg~1 levels. Direct effects on wheat were discussed in earlier publication. The dry matter yield and P uptake by first succeeding crop (maize-I) were 1.69 to 2.93 times as much as that of second succeeding crop (maize-II). The dry matter (DM) yield and P uptake by both maize crops and available P content of soil progressively increased with increasing levels of P applied to preceeding wheat crop and initial available P status of soil. Both the P fertilizers were equally effective. The utilization of added P was 9.3 to 19.1percent by maize-I and 5.1 to 10.1percent by maize-II. Results evidenced that the fraction of residual P which was not extractable in 0.5 N NaHCO_3 was utilized by the maize crop and the availability of such reaction products was more to maize-I than maize-II.