Years of fertilization and liming impacts on surface versus deep soil organic carbon sequestration in a sub-tropical Alfisol

Abstract

Minimizing elevated CO2 concentration in atmosphere and increasing soil organic carbon (SOC) stock can be achieved through appropriate soil management practices. Hence, this study was conducted to understand the effect of 60 years of fertilization and liming in an Alfisol under sub-tropical climatic condition under a maize (Zea mays L.)-wheat (Triticum aestivum L.) cropping system on SOC sequestration in surface (0-30 cm) and deep (30-60 cm) soil layers. In farmyard manure (FYM; added on equivalent recommended nitrogen basis) with adjusted doses of phosphorus and potassium coupled with liming (FYMP'K'L) treated plots, total SOC was nearly 83 % higher than unfertilized control plots in the 0-30 cm soil layer. Labile C including KMnO4-C was more in plots with FYM than NPKL plots, whereas the recalcitrant C content was more in NPKL than FYM treated plots. In the 0-60 cm soil layer, labile C stock was highest for FYMP'K'L plots, but recalcitrant C stock was highest for NPKL. Total SOC accumulation rate (over unfertilized control plots) was highest for FYMP'K'L plots (0.38 Mg ha-1 year-1) in the surface soil layer, whereas C sequestration rate was highest for NPKL plots (0.18 Mg ha-1 year-1) in that layer. Both total SOC accumulation and SOC sequestration rates were highest for NPKL plots in the deep soil layer. Averaged across all treatments, total SOC sequestrations (over unfertilized control plots) in surface and in deep soil layers were 0.09and 0.08 Mg ha-1year-1 in 60 years. Overall, NPKL management practice had highest C sequestration potential in this agro-ecosystem thereby offsetting CO2emission, while liming with application of FYM (based on equivalent recommended mineral N fertilization) and adjusted doses of PK (FYMP'K'L) was the next best management practice.