Soil carbon, micronutrients and microbiological dynamics under cash crop-based cropping systems in semi-arid National Capital Region of India

Cropping systems and nutrient management practices potentially alter microbiological properties and nutrients bioavailability in soils. This study evaluated the footprints of prevalent cash crops-based cropping systems at farmers’ fields (> 10 years) on total carbon (TC), total inorganic carbon (TIC), soil organic carbon (SOC), micronutrients as well as biological activities. The soils faced rice–wheat (RW) cropping system exhibited significant accrual in SOC (29.16%) over pearl millet-wheat (PW). Higher dissolved organic carbon (DOC) content was obtained in soils from sugarcane-sugarcane (SS) mono-cropping with a magnitude of 4.75, 9.01, 11.71 and 45.35% with respect to PW, RW, cotton-wheat (CW) and pearl millet-mustard (PM), respectively. Accretion of TIC (4.92 g kg−1) and TC (11.26 g kg−1) contents were acquired in soils experienced PM and SS cropping systems, respectively. DTPA-extractable micronutrients except copper (Cu) were found in higher concentration under RW compared to other cropping systems. In soils of RW cropping system, SOC, microbial biomass carbon (MBC), dehydrogenase activity (DHA) and DTPA-extractable Zn, Mn and Fe were higher by 3.33 to 58.97, 1.94 to 27.40, 23.81 to 51.59, 12.12 to 85.00, 25.73 to 58.05 and 15.17 to 83.44%, over other persisted systems. Despite the lesser chemical fertilization and manure addition, soils faced SS mono-cropping statistically reflected similar values to RW cropping system for most of studied properties. Two main canonical discriminant functions (CDFs), based on SOC, DOC, TIC, TC, DTPA-extractable micronutrients (Mn, Zn, Fe, and Cu), MBC and DHA, clearly differentiated the cropping systems and both CDFs explained 92.3% variance of the total variation. Principal component analysis (PCA) picked out MBC, SOC, pH and EC as most influential variables in evaluating soil status across various cropping systems. Additionally, two principal components (PCs) explained 73.7% of total variance in original dataset, underscored the major factors influencing soil properties under varied cropping techniques. Among the studied cropping systems, RW was found superior in relation to the soil microbial activity and nutrient availability. However, SS mono-cropping also exhibited comparable results to RW and proved better over other aerobic cropping systems, especially in terms of carbon dynamics and microbiological properties of soils.