Soil Organic Carbon Pools in Benchmark Soils of Punjab, Pakistan

Soil organic carbon (SOC) in agricultural soils is important for sustainable global food security and environmental protection. In the present study, carbon pools of varying lability and SOC stock were assessed in benchmark soils under different cropping systems of Punjab, Pakistan. Among all the benchmark soils, the very labile carbon-VLC pool accounted for a higher proportion of TOC with a mean of 37.44% followed by non-labile carbon-NLC (22.08%), less labile carbon-LLC (20.86%) and labile carbon-LC (19.46%) pool. Similarly, the VLC pool was found higher in all the cropping systems than the LC, LLC and NLC pools. The maximum VLC concentration (0.175%) was found in cotton-wheat followed by maize-wheat (0.162%) and rice-wheat (0.155%) cropping system whereas the minimum VLC was observed in fallow-wheat (0.104%) cropping system. A significant positive correlation was recorded among all the carbon pools. Moreover, the SOC stock concentration in heavy texture benchmark soils was significantly higher than light texture soils while difference with medium texture soils was non-significant. The distribution of SOC stock in cropping systems was found in the following order; cotton-wheat>rice-wheat>maize-wheat>fallow-wheat. Hence, it was concluded that the carbon pools and SOC stock are governed by soil texture and management practices.