Mineralization of carbon (C) is a burning issue that is regulated by soil attributes. It has direct impacts on crop productivity and quantification of organic residue addition in soil. For better understanding and achievement of potential tillage benefits, a comprehensive scientific understanding of C mineralization is very important. Therefore, a laboratory incubation experiment was conducted to investigate the C mineralization rates and kinetics of crop residues (rice and maize) when applied on the surface (as zero-tillage, ZT) and incorporation (as conventional tillage, CT) in four different soil types (S1 and S2 of Entisol; S3 and S4 of Inceptisols) of West Bengal state, India. Results showed that after 7 days of incubation, there was a rapid phase of decrease in CO₂-C fluxes. It continued up to day 14 followed by a sluggish nature of CO₂ emission up to day-42, and after that almost levelling off in all subsequent periods up to the end of 126 days of incubation. There was a progressive release of cumulative total C from the soils with an increase in time till the last day of incubation. For every 10% increase in C loss, there was about 0.376 mg/g C mineralization from the applied residue C. It was evident from the kinetic models that C mineralization from the residues followed the exponential model: C = Co(1 − e^−kt). Similar rate constant (k) values were recorded in both placement methods, but the rate of maximum potential mineralizable (C₀k) residue C was higher under residue incorporation treatments for both rice and maize residue. However, the rice and maize residues showed almost similar amounts of C mineralized over time when applied on the surface. The future prediction analysis using the equation C = Co(1 − e^−kt) suggested that the residues incorporated into the soil releases a maximum C irrespective of residue type. We conclude that the residues when incorporated into the soil significantly increases the C footprints through maximum C mineralization; leaving the crop residue on the soil surface reduces the C footprints which helps in achieving sustainability from an environmental perspective.

The rate of change in the relative amount of active and passive carbon (AC and PC) due to the land management practices (cropping systems combined with tillage) may vary with soil types depending on their level of chemical and/or physical protection from the decomposition but has rarely been directly measured. We have quantified the C storage potentiality of different soil types, namely old alluvial Inceptisol of Malda and recent alluvial Entisol of Coochbehar in West Bengal (subtropical eastern India) under the influence of different cropping systems (rice-maize: RM and rice-wheat: RW) and tillage practices (zero-tillage: ZT and conventional tillage: CT). The key objective was to demonstrate the short-term impact of conservation agriculture (CA) on soil C dynamics over the conventional practice. Research revealed that after short-term CA, total organic carbon (TOC), AC, PC, and total nitrogen (TN) showed significant (p < 0.05) improvement under the RM cropping system over the RW. The highest TOC content under the RM cropping system was recorded in the sites of Malda over the Coochbehar sites. The ZT significantly (p < 0.05) enhanced the TOC in the upper layers (0–5 and 5–10 cm) and the CT showed improvements in the lower depths (10–20 cm). We observed some irregular variations in the interactions of the cropping system and tillage with respect to different sites. However, the ZT performed better in improving C fractions under RM and RW as compared to CT. The TOC and TN stocks were maximum in the lower depth which was evident in both soil types. The TOC linearly regressed on TN accounted for 94.2% variability (R² = 0.942) of the C accumulation in soil and vice-versa. The PC was in a significant relationship with TN (R² = 0.943), but AC was moderately regressed (R² = 0.851). Lower stratification ratio values in Coochbehar soils (sandy loam in texture) indicated higher profile distribution of AC and PC in the soil profile; while in the Inceptisol, accumulation of the C fractions on the soil surface due to heavy texture resulted in the higher stratification values. The novelty of this study is that old alluvial Inceptisol showed a comparatively greater amount of AC and PC storage capability in comparison with the new alluvial Entisol. Conclusively, our study demonstrated that the adoption of conservation agriculture (CA practice/ZT) in cropping systems with higher C biomass input would significantly enhance the AC and PC fractions; however, the amount of storage is highly governed by the soil type and climatic factors.

A field study was conducted from 2021 to 2023 in a rice–wheat cropping system in the Terai agro-ecological zone of West Bengal, India, using different management practices, i.e., tillage (conventional tillage, CT, and zero tillage, ZT), crop residue (R), and plant growth-promoting bacteria (B). This study was a part of long-term research on resource conservation technology (conservation agriculture, CA), undertaken on a research farm in Uttar Banga Krishi Viswavidyalaya, Pundibari (Cooch Behar), West Bengal. The project was established in 2006 in acidic alluvial soil. The aim of this study was to evaluate rice–wheat productivity, nutrient uptake, soil quality, and profitability after the 16th and 17th crop cycles under the above-mentioned management practices. The results revealed that the pooled yield of rice grain and straw was significantly higher under the CT + R + B treatment than under the other treatments (ZT, ZT + B, ZT + R, ZT + R + B, CT, CT + B, and CT + R). However, the wheat grain and straw yields were significantly greater under the ZT + R + B treatment than under other treatments. The system’s grain yield and straw yield were significantly higher under the CT + R + B treatment, on par with ZT + R + B, compared to the other treatments. Nutrient uptake (nitrogen, N; phosphorus, P; and potassium, K) was increased by retaining R and inoculating B compared to the sample without R and without B. Soil properties, including organic carbon, available N, available P, and available K, were improved in all the treatments compared to the initial values, but the impact was greater in the treatments with R and B than in those without R and without B. In the 5–10-cm soil layer, the above-mentioned soil properties were also improved over the initial (2006) values by 37, 126, 65 and 60%, respectively, by applying the best treatment (ZT + R + B). In economic terms, the benefit–cost ratio was significantly higher under the CT + R + B treatment for rice crops (2.99) and ZT + R + B for wheat crops (3.37). Therefore, we can conclude that, after 17 years of cultivation, for rice, CT performs better than ZT; meanwhile, for wheat cultivation, ZT produces greater yields than CT in the Terai agro-ecological zone of West Bengal, India.