Sustainable Cropping Sequences to Improve Soil Fertility and Microbiological Properties

Different cropping systems and nutrient management techniques impact the microbiological characteristics of soil and nutrient availability for plants. This study assessed four cropping systems—rice–wheat, cotton–wheat, pearl millet–wheat, and pearl millet–mustard in Hisar district, Haryana, using 80 soil samples (20 from each system) collected in April 2022 after the Rabi crop harvest. The cotton–wheat system had the highest accessible nitrogen (N) at 155.9 kg ha−1, while both the cotton–wheat (59.3 kg ha−1) and rice–wheat (54.0 kg ha−1) systems had higher available sulfur (S) levels compared to pearl millet–wheat (41.2 kg ha−1). Pearl millet–wheat also showed 12.4% higher potassium (K) levels than rice–wheat. The rice–wheat system exhibited the highest phosphorus (P) concentration at 54.3 kg ha−1 and greater DTPA-extractable micronutrients. Soils from the rice–wheat system had higher DTPA-extractable micronutrients (Zn, Fe, Mn, Cu) and superior microbial biomass nitrogen (MBN, 54.7 mg kg−1), urease (37.9 µg NH4+-N g−1 h−1), and alkaline phosphatase activity (APA, 269.7 µg PNP g−1 h−1) compared to other systems. Canonical discriminant functions explained 88.1% of the variability among cropping systems, while principal component analysis identified available P, DTPA-extractable Zn, and Cu as key soil quality indicators, accounting for 66.9% of the variance. These insights can inform policymakers on promoting effective cropping systems and sustainable soil health in northwestern India.