Sustaining soil fertility remains a major challenge in semi-arid regions due to chronic water scarcity and inherently low soil organic matter. We assessed long-term (>10 years) effects of four dominant cropping systems—pearl millet ( Pennisetum glaucum )–wheat ( Triticum aestivum ), pearl millet–mustard ( Brassica juncea ), cotton ( Gossypium hirsutum )–wheat, and cluster bean ( Cyamopsis tetragonoloba )–wheat on soil carbon pools, microbial properties, nutrient availability and inorganic phosphorus (P) fractions in coarse-textured soils of south-western Haryana, India. Surface soils (0–15 cm) from 80 fields (20 per system) were analysed and multivariate statistics i.e. discriminant function analysis (DFA) and principal component analysis (PCA) were used to compare these systems. The soils under pearl millet–wheat showed the highest soil organic carbon (SOC: 2.9 g kg -1 ), dissolved organic carbon (DOC: 21.4 mg kg -1 ), microbial biomass carbon (MBC: 128.6 mg kg -1 ), available N (139.3 kg ha -1 ) and dehydrogenase activity (31.7 μg TPF g -1 soil 24 h -1 ), while cluster bean–wheat had the lowest biological indicators. The pearl millet–mustard rotation exhibited the largest pools of available P (17.8 kg ha -1 ) and inorganic P (saloid-P, Al-P, Fe-P, Ca-P) as well as alkaline phosphatase activity (74.9 μg PNP g -1 h -1 ). Among studied cropping systems, total inorganic P (TPi) and total P (TP) followed the sequence: pearl millet–mustard > pearl millet–wheat > cotton–wheat > cluster bean–wheat. We found that SOC, DOC, MBC, microbial biomass nitrogen (MBN) and dehydrogenase activity were the most diagnostic indicators of soil fertility, hence soil health across the cropping systems. Pearl-millet-wheat offers the best balance of soil C and biological activity, whereas pearl millet-mustard builds soil P reserves. Thus, cropping-system choice strongly regulates carbon accretion, microbial functioning and P dynamics, thereby ensures soil health in semi-arid subtropical soils. • Pearl millet–wheat cropping system substantially increased soil organic carbon (SOC) and dissolved organic carbon (DOC). • Pearl millet–wheat rotation enhanced soil microbial biomass C and N (MBC, MBN) and dehydrogenase activity. • Pearl millet–mustard system recorded the highest concentrations of available P, P activation coefficient and all inorganic P fractions. • Cotton–wheat cropping system maintained lower available P, K, and S compared with pearl millet–based systems. • Pearl millet–wheat and pearl millet–mustard rotations emerged as the most sustainable systems for semi-arid subtropical regions.
Prakash et al. (Wed,) studied this question.