Carbon density and accumulation in agroecosystem of Indo-Gangetic Plains and Vindhyan highlands, India.

In agroecosystems, the annual carbon (C) inputs to soil are one of the most promising greenhouse gas mitigation options. Net primary productivity (NPP) provides the inputs of C in ecosystems that can potentially be sequestered in soil organic matter. In this study, we estimates the C density and accumulation rate in rice-wheat agroecosystem at four sites of Indo-Gangetic Plains and Vindhyan highlands through amalgamation of ground truth (GT) and remote sensing (RS) approach. In addition to this, we validated field-measured aboveground net production (ANP) with remotely sensed SPOT-Vegetation data. ANP of the sites ranged from 6.8 to 11.1 and 3.3 to 8.8 t-C ha(-1) year(-1) for GT and RS, respectively. Both estimates (GT and RS) were linearly and significantly related with each other (y = 1.33x - 5.82, R (2) = 0.93, P = 0.04; where x = GT ANP and y = RS ANP). For the whole region, total NPP (rice + wheat) was ranged from 7.9 to 12.5 t-C ha(-1) year(-1). The C accumulation potential of the present agroecosystems was 9.1 and 1.9 t-C ha(-1) year(-1) in the form of ANP and belowground NPP (BNP), respectively. The aboveground C stock of agroecosystem allocated in foliage (7.8 %), stem (57.6 %), and grain (35.1 %). Survey about the fate of post-harvested materials indicated that aboveground portion of the crop is almost used completely within the year for different purposes including human consumption and cattle feeding. Therefore, only BNP and litter contribute to long-term C sequestration. Since agroecosystem has enormous potential to sequester C, better management of aboveground portion NPP of the crop may enhance C sequestration potential of agroecosystem.