SOIL AGGREGATION AND ORGANIC CARBON AS AFFECTED BY DIFFERENT IRRIGATION AND NITROGEN LEVELS IN THE MAIZE–WHEAT CROPPING SYSTEM

SUMMARYBest management practices in agriculture have the potential to sequester carbon and improve soil aggregation. Hence, in the present investigation, different levels of irrigation and nitrogen (inorganic and organic) were used in the maize–wheat cropping system to study their effect on soil organic carbon (SOC) accumulation and aggregation. The treatments consisted of three levels of water regimes (namely W1, W2 and W3 referring to limited, medium and maximum irrigation) and five nitrogen levels (T1, 0% N; T2, 75% N; T3, 100% N; T4, 150% N; T5, 100% N from organic source), with three replications taken in a split plot design. Positive and significant correlation between SOC and mean weight diameter (MWD) was observed, implying that increasing SOC improved soil structure and increased the MWD. The quantification of water and nitrogen interaction on SOC was done by developing a multiple regression equation, which, when validated with SOC of the subsequent year, resulted in significant correlation. Irrigation and N was found to have a significant effect on soil aggregation and organic carbon build-up. Two N treatments (T4: 150% N and T5: 100% N from organic source) improved soil aggregation (macro-aggregates) and SOC when accompanied with W3 water regime (maximum amount of irrigation). Across N treatments, the W3 regime registered significantly higher SOC by more than 30% over control in the 0–15-cm soil depth.