Nitrogen and rice straw incorporation impact Zn fractions and wheat yield in rice-wheat system

A long-term experiment was conducted at research farm of department of Soil Science, PAU to investigate the impact of rice straw incorporation (0-10 t/ha/yr) and fertilizer N (0-150 kg N/ha) application on wheat yield and Zn fractions after 7 years (2010-17). The treatments were arranged in a split plot design with three replications, N (N-0, N-90, N-120 and N-150) in main plots and rice straw (RS0, RS5, RS7.5 and RS10) in sub-plots. Zinc fractions were significantly increased with graded levels of RS incorporation. The greater part of total-Zn was present in residual form and only a minute part was present in readily available forms, i.e. WS+EX form. Regardless of the treatments, relative preponderance of these Zn fractions was: WS+EX Zn Zn <SpAd-Zn <MnOx-Zn < OM-Zn<AFeOx-Zn <CFeOx-Zn < Res-Zn in soil. RS incorporation was found to increase all the Zn fractions and significantly higher concentration was found at RS10. Correlation analysis has shown that soil organic carbon was significantly and positively correlated with Zn fractions. The grain yield of wheat in 120 kg N/ha and 10 t/ha RS incorporation plots were significantly higher than in the control. DTPA- extractable Zn was found to be and positively correlated with Zn fractions.