Vol. 11, Issue 3 (2022)

Author(s):
K Lokeshwar, RK Naresh, SP Singh, PC Jat, Manisha, Kushal Sachan, Rajaram Choudhary and Mohd. Shah Alam

Abstract:
Labile organic carbon (LOC) fractions are considered as sensitive indicators of change in soil quality and can serve as proxies for soil organic carbon (SOC). Although the impact of tillage, fertilization and crop residue management on soil quality is well known, less is known about LOC and SOC dynamics in the rice- wheat production systems in North West India. Tillage was the main factor to influence SOC and LOC fractions under the rice-wheat cropping system in North West India. NT increased SOC and all LOC fractions compared to CT. An increase in residue retention led to an increase in microbial biomass carbon (MBC). Plots under NT–NT had about 10% higher coarse (250–2000 μm) intra-aggregate particulate organic matter-C (iPOM–C) within >2000 μm sand free aggregates in the 0- to 5-cm soil layer compared with CT–CT plots. The fine (53–250 μm) iPOM–C within the 250- to 2000-μm aggregates was also higher in the continuous NT plots compared with CT within both >2000 and 250 to 2000 μm sand free aggregate size classes in that soil layer. Macro-aggregates (>0.25 mm) constituted 32.5–54.5% of total water stable aggregates (WSA) and were linearly related (R² = 0.69) to soil organic carbon content. The addition of rice straw and FYM significantly improved the formation of macro-aggregates with a concomitant decrease in the proportion of micro-aggregates at all the three sampling depths (0–5, 5–10 and 10–15 cm). Macro-aggregates had higher C and N density as compared to micro-aggregates. Application of rice straw and FYM improved C and N density in different aggregate sizes and the improvement was greatest in plots that received both rice straw and FYM each year. Application of FYM along with inorganic fertilizer resulted in a net C sequestration of 0.44 t ha^-1 in the plough layer of rice–wheat cropping.