Soil organic carbon stock variability in the Northern Gangetic Plains of India: interaction between agro-ecological characteristics and cropping systems

摘要

Soil organic carbon (SOC) content and its spatial distribution in the Northern Gangetic Plain (NGP) Zone of India were determined to establish the cause-effect relationship between agro-ecological characteristics, prevailing crop management practices and SOC stock. Area Spread Index (ASI) approach was used to collect soil samples from the NGP areas supporting predominant cropping systems. Exponential ordinary kriging was found most suitable geo-statistical model for developing SOC surface maps of the NGP. Predicted surface maps indicated that 43.7% area of NGP had 0.5-0.6% SOC, while the rest of the area was equally distributed with high (0.61-0.75%) and low (0.5%) SOC content levels. Averaged across cropping systems, maximum SOC content was recorded in Bhabar and Tarai Zone (BTZ), followed by Central Plain Zone (CPZ), Mid-Western Plain Zone (MWPZ), Western Plain Zone (WPZ) and South-Western Plain Zone (SWPZ) of the NGP. The SOC stock was above the optimum threshold (>12.5Mg/ha) in 97.8, 57.6 and 46.4% areas of BTZ, CPZ and MWPZ, respectively. Only 9.8 and 0.4% area of WPZ and SWPZ, respectively, had SOC stock above the threshold value. The variation in SOC stock was attributed largely to carbon addition through recycling of organic sources, cropping systems, tillage intensity, crop or residue cover and land-use efficiency, nutrient-use pattern, soil texture and prevailing ecosystem. Adoption of conservation agriculture, balanced use of nutrients, inclusion of legumes in cropping systems and agro-forestry were suggested for enhancing SOC stock in the region.