Assessment of soil organic carbon stocks in relation to variation in physiography under sub-mountainous Shiwalik ranges of lower Himalayas, India.

A study was conducted in lower Shiwaliks of Punjab, India to study the soil organic carbon (SOC) stock variation in hill, piedmont plain and alluvial plain regions of Punjab, and further to investigate the SOC variability down the slope in the lower Shiwaliks region of Punjab. The SOC fractions viz. very labile carbon, labile carbon, less labile carbon and recalcitrant were determined using standard methodologies. The total SOC stock in 0–60 cm soil depth was highest in plain region (31.81 Mg ha−1), followed by piedmont (23.43 Mg ha−1) and lowest in hill region (22.86 Mg ha−1). Whereas, the SOC concentration in surface layer was highest in foot slope (5.76 g kg−1) followed by mid slope (4.14 g kg−1) and lowest in up slope (2.32 g kg−1). Among the SOC fractions the average labile carbon content in soil samples was found in the order, hills (0.81 g kg−1) > piedmonts (0.73 g kg−1) > plains (0.50 g kg−1). The soil bulk density (Db) was higher in the plain than that of piedmont and hills. Moreover, a similar trend is observed in case of water holding capacity. Regression analysis has revealed significant relationship between Db and SOC stock at p < 0.05. Further, analysis of variance (ANOVA) at p < 0.05 has indicated significant differences among concentration of SOC and stock influenced by land use and soil depths. Thus, an understanding of the effect of physiography on SOC via such studies is important for soil quality management. [ABSTRACT FROM AUTHOR]