Carbon dynamics in rice-wheat cropping system under conservation tillage in Haryana

Abstract

Tillage intensive cropping practices have deteriorated soil physical qualities and decreased soil organic carbon (SOC) level in rice-growing areas. Consequently, crop productivity has declined over the years demonstrating the need of sustainable alternatives. Given that, a field survey was conducted in the Jhajjar district of Haryana to assess the distribution and stability of SOC fractions under conservation tillage practice. Soil samples were collected from four sites (Subana, Palra, Baghpur, Khatiwas) at four depths (0-5cm, 5-15 cm, 15-30 cm, and 30-45 cm). Among all the sites, Palra shows the maximum values of TOC (8.84) and all the four carbon fractions (Cfrac1, Cfrac2, Cfra3 and Cfrac4) (1.59, 1.07, 1.76 and 4.32), indicating better carbon stabilization and sequestration potential while lowest values were shown by Subana (6.72) (1.45, 0.96, 1.56 and 2.78). Results show that TOC and labile carbon were highest in surface layers and decreased with depth. A strong correlation was observed between TOC and non-labile carbon fractions (R² > 0.935), highlighting their role in long-term carbon storage. The active-to-passive carbon ratio and lability index varied significantly, serving as sensitive indicators of carbon turnover. Lability index was also observed highest in Subana (1.17) which shows the presence of more amount of labile carbon fractions, while Palra (0.97) shows the presence of more stable carbon pools. Notably, higher passive C-pool in conservation tillage practices sites suggest that it could stabilize the recalcitrant form of carbon that persist longer in the soil. Therefore, conservation tillage practice could be recommended in tropical rice-based cropping system for improving soil quality and productivity sustainability.