Residual phosphorus and zinc influence wheat productivity under rice-wheat cropping system.

Continuous cropping of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) deplete soil fertility and crop productivity. One strategy to increase crop productivity under rice-wheat system is balanced application of crop nutrients. Field experiment was conducted to assess the impact of phosphorus (0, 40, 80, 120 kg P ha(-1)) and zinc (0, 5, 10, 15 kg Zn ha(-1)) on the productivity of rice genotypes (fine and coarse) and their residual effects on the grain yield (GY) and its components (YC) of the succeeding wheat crop under rice-wheat cropping system (RWCS) in North Western Pakistan during 2011-12 and 2012-13. After rice harvest in both years, wheat variety "Siren-2010" was grown on the same layout but no additional P, K and Zn was applied to wheat crop in each year. The GY and YC of wheat significantly increased in the treatments receiving the higher P levels (120 > 80 > 40 > 0 kg P ha(-1)) and Zn (15 > 10 > 5 > 0 kg Zn ha(-1)) in the previous rice crop. The residual soil P and Zn contents after rice harvest, GY and YC of wheat increased significantly under low yielding fine genotype (B-385) as compared to the high yielding coarse genotypes (F-Malakand and Pukhraj). The residual soil P and Zn, GY and of wheat increased significantly in the second year as compared with the first year of experiment. These results confirmed strong carry over effects of both P and Zn applied to the previous rice crop on the subsequent wheat crop under RWCS.