Distinct changes in soil organic matter quality, quantity and biochemical composition in response to land-use change to diverse cropping systems and agroforestry in north-western India

The quantification of change in total organic carbon (TOC) pool and its fractions in relation to altered soil enzymatic activity during long-term vegetation refurbishment is considered critically important for managing and restoration of landscapes. Landscapes have contrasting impacts on soils’ biochemical and biological composition, which eventually affect soil aggregation, carbon (C) fractions and enzyme activities. We therefore, examined the response of different landscapes viz. poplar-based agroforestry, rice–potato–maize, rice–wheat and maize–wheat cropping vis-à-vis uncultivated soils of north-western India on soil aggregation, C fractions and enzyme activities. We hypothesized that both plants mediated C and exogenous C input would exert differential impacts on organic C pool in soils under different landscapes in response to diverse cropping practices. Landscapes significantly (p < 0.05) influenced microbial activities, soil enzymes, C fractions, TOC and the process of soil aggregation. Soils’ physical, chemical and biological properties were significantly improved under poplar-based agroforestry system, following rice–potato–maize system, whilst had the lowest effect in the uncultivated soils. The uncultivated landscapes significantly lost TOC by ~ 1.6, 2.1, 2.9 and 2.7-times, respectively than the soils under maize–wheat, rice–wheat, rice–potato–maize and poplar-based agroforestry. Rice–potato–maize cropping resulted in ~ 13.6% higher C stabilization in passive C pool, compared with rice–wheat cropping system. Macro-and micro-aggregates formation was significantly improved due to establishment of poplar-based agroforestry as well as rice–potato–maize systems over the others. Correlation matrix elucidated easily extractable glomalin concentration as potential determinant influencing soil enzymatic activity; e.g. cellulase (r = 0.854**; p < 0.01) and xylanase (r = 0.969**; p< 0.001 ). These results enlightened knowledge on soil aggregation, C fractions and enzyme activities in different landscapes, which help enhance C sequestration and eventually the C restoration in studied landscapes. This study suggests that to overcome problems originated from intensive rice–wheat cropping system for which poplar-based agroforestry and rice–potato–maize system could be another best option.