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Under the rice–wheat cropping system (RWS), the continuous cropping of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) deplete soil fertility, and reduce crop growth and total rice biomass. In RWS, both phosphorus (P) and zinc (Zn) deficiencies are considered important nutritional constraints for reducing rice crop growth rates (CGR) and total biomass/biological yield (BY). The objective of this experiment was to investigate the impact of phosphorus (0, 40, 80, 120 kg P ha−1) and zinc rates (0, 5, 10, 15 kg Zn ha−1) on CGR and BY of three rice genotypes [fine (Bamati-385) versus coarse (Fakhre-e-Malakand and Pukhraj)] in Northwestern Pakistan during summer 2011 (Y1) and 2012 (Y2). The results revealed that higher CGR at various growth stages and total BY was obtained with the integrated use of higher phosphorus (80 and 120 kg P ha−1) and zinc rates (10 and 15 kg Zn ha−1). The lower CGR and BY were recorded when P and Zn were not applied (control) or when P and Zn were applied alone. In the case of rice genotypes, the highest CGR and BY were recorded for the hybrid rice (Pukhraj) than the other two genotypes. The CGR was increased to the highest level at the heading stage as compared to tillering and physiological maturity. The increase in CGR had a positive impact on the total BY of rice cultivars. The increase in BY had a positive relationship with grain yield and grower's income. It was concluded from the study that the combined application of higher P and Zn rates to the coarse rice genotypes (Fakhre-e-Malakand and Pukhraj) could increase CGR, total BY, crop productivity and profitability. [ABSTRACT FROM AUTHOR]

Continuous cropping of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) deplete soil fertility and reduce crop productivity as well as zinc (Zn) concentrations in rice grains and straw. Low Zn concentrations in rice grains have a negative impact on human health, while low Zn concertation in rice straw creates a nutritional problem for animals. The current high yielding rice varieties and hybrids remove large quantities of Zn from the soils, lowering the residual concentrations of soil Zn for the subsequent crop (e.g., wheat). Field experiments were conducted on farmers field in Malakand with the objective to evaluate the impact of various combinations of phosphorus (0, 40, 80, and 120 kg ha−1) and Zn levels (0, 5, 10, and 15 kg ha−1) on biofortification of Zn in grains and straw of rice genotypes [fine (Bamati-385) vs. coarse (Fakhre-e-Malakand and Pukhraj)]. The results revealed that Zn biofortification in rice genotypes increased with the integrated use of both nutrients (P + Zn) when applied at higher rates (80 and 120 kg P ha−1, and 10 and 15 kg Zn ha−1, respectively). The biofortification of Zn in both grains and straw was higher in the coarse than fine rice genotypes (Pukhraj > Fakhre-e-Malakand > Basmati-385). It was concluded from this study that the application of higher P and Zn levels increased Zn contents in rice parts (grains and straw) under the rice-wheat system. We also concluded from this study that Zn concentrations in rice grains and straw are influenced by plant genetic factors and Zn management practices. [ABSTRACT FROM AUTHOR]

Continuous cropping of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) deplete soil fertility, reduced crop productivity, and grower's income. Phosphorus (P) and zinc (Zn) deficiencies are considered important nutritional constraints under rice-wheat cropping system. One strategy to increase crop productivity and grower's income under the rice-wheat system is the balanced application of P and Zn fertilizers. The objective of this research was to evaluate the impact of sole and various combinations of P (0, 40, 80, and 120 kg ha−1) and Zn levels (0, 5, 10, and 15 kg ha−1) on productivity (grain yield and yield components) and profitability (net returns) of different rice genotypes (cultivars) (fine (cv.Bamati-385) vs. coarse (cv. Fakhre-e-Malakand and cv. Pukhraj)) and their residual effect on the income of the succeeding wheat crop (cv. Siran-2010). The results revealed that both rice and wheat productivity and profitability was higher with the combined application of both nutrients at higher rates (80 and 120 kg P ha−1 and 10 and 15 kg Zn ha−1). The highest productivity and profitability was obtained with the cultivation of hybrid rice "Pukhraj" (Pukhraj > Fakhre-e-Malakand > Basmati-385). It was concluded from this study that application of higher P and Zn levels and growing of hybrid rice increased productivity and profitability under the rice-wheat cropping system. [ABSTRACT FROM AUTHOR]