An on-going long term field experiment started in Rabi 1995 at the Research Farm of the Department of Soil Science, Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana (India) under the pearl millet-wheat cropping system was selected to study the effect of long-term application of organic manures and fertilizers on soil organic carbon and microbiological properties. Highest soil organic carbon (SOC: 1.18 %), dissolved OC (DOC: 64.74 mg kg⁻¹) content, microbial biomass C (MBC: 618.40 mg kg⁻¹), dehydrogenase (DHA: 72.83 μg TPF g⁻¹ 24 hr⁻¹), alkaline phosphatase (APA: 685.44 μg PNP g⁻¹ soil hr⁻¹) and aryl sulfatase (ASA: 12.56 μg PNP g⁻¹ soil hr⁻¹) activities were observed with the application of 15 Mg FYM+150 kg N+30 kg P₂O₅ ha⁻¹. Integrated application of chemical fertilizers with pressmud showed superiority in the improvement of microbial biomass nitrogen (MBN: 73.73 mg kg⁻¹) and urease activity (69.54 μg NH₄⁺ g⁻¹ hr⁻¹) than FYM or poultry manure plus NP. Beneficial impacts of the sole application of organic manures on SOC, DOC, MBC content, DHA, APA, and ASA were found in order as: FYM > pressmud > poultry manure. Impacts of nutrient management practices on soil carbon fractions decreased with depth. Poultry manure application, either alone or in combination with NP fertilizers was inferior to FYM and pressmud. The SOC had a positive relationship with MBC (R² = 0.95) and MBN (R² = 0.75) and, also showed a highly positive and significant correlation with microbiological properties of soil. This dynamic equilibrium among soil properties indicated that the nutrient management practices that improve SOC could lead to improve soil fertility and accrued microbiological properties in these soils. This study revealed that conjuctive use of organic manures and chemical fertilizers have positive impact on soil fertility and microbiological properties as compared to sole application of organic manures or fertilizers; and among organic manures, FYM was superior to pressmud followed by poultry manure.

Information on phosphorus (P) release kinetics and sorption–desorption in soils is important for understanding how quickly reaction approaches equilibrium and replenishes the depleted soil solution. Laboratory experiments were conducted to study the P release and sorption–desorption kinetics in soils differing in clay, soil organic carbon (SOC), available P, and calcium carbonate (CaCO₃) contents. Phosphorus release from soils proceeded in two phases: initially faster phase followed by a slower phase as equilibration progressed. Elovich equation (R² ≥ 0.97**) described well the P release versus time data. P release coefficients for power function were significantly correlated with available P and SOC. Freundlich sorption constants increased with increase in clay and CaCO₃ content. With increase in SOC and available P concentration in soils, substantial reduction in sorption constants was observed. It was concluded that for efficient P management, it is important to take into account soil texture, the existing soil P level, SOC content, and soil calcareousness.

Information on the long-term effects of the addition of organics and fertilizers to wheat under the pearl millet–wheat cropping system with semi-arid conditions in north-western India is still lacking. The present research was conducted in an ongoing field experiment initiated during Rabi 1995 at the Research Farm of Chaudhary Charan Singh at Haryana Agricultural University, Hisar. After 25 years, the impacts of nutrient management practices on soil fertility and wheat productivity were evaluated. The experiment comprised a total of eight treatment combinations viz. half and full doses of recommended fertilizers (N and P), organic manures (FYM: farmyard manure, POM: poultry manure, and PRM: press mud) alone and in combination with NP fertilizers. The conjoint application of organic manure and chemical fertilizers resulted in a positive influx of nutrients via increasing total organic carbon (TOC), available N, P, K, and S, which ranged from 0.46 to 1.42%, 122.70 to 194.70, 15.66 to 74.92, 340.5 to 761.2, and 15.26 to 54.63 kg ha⁻¹ in surface soil (0–15 cm), respectively. Carbon fractions and crop yield were significantly improved by adopting integrated nutrient management (INM). The TOC showed a positive and significant correlation with C fractions (r > 0.92) and with soil-available N, P, K, and S (r > 0.77) content. The data also revealed a strong relationship between TOC and soil-available (0–15 cm) nutrients i.e., available N (R²= 0.769), available P (R² = 0.881), available K (R² = 0.758), and available S (R² = 0.914), respectively. Thus, practices that increased TOC were also beneficial in enhancing the availability of the nutrients in the soil. A positive and highly significant correlation was also found among wheat yield, nutrient (NPKS) content, and uptake. A polynomial relationship between grain yield and grain N (R² = 0.962), P (R² = 0.946), and K (R² = 0.967) content, and between straw yield and straw N (R² = 0.830), P (R² = 0.541) and K (R² = 0.976) content was obtained. Integrated use of PRM_7.5 followed by FYM₁₅ and POM₅ coupled with NP fertilizers proved best, which could be beneficial for obtaining nutritious and highest wheat yield (grain: 6.01 t ha⁻¹ and straw: 7.70 t ha⁻¹) coupled with improved fertility within a sustained manner under the pearl millet–wheat sequence in prevailing semi-arid conditions of the North Indian state of Haryana.

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.

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.