Management strategies in agroecosystems may influence C balance in soil through variation in C input to soil and also by causing variation in C output from soil. In a two year study we evaluated the effect of application of soil inputs with varying resource quality viz: high quality (C:N 16; HQR), low quality (C:N 82; LQR) and mixed quality (HQR +LQR; MQR) inputs having equivalent amount of N, on the soil CO 2 flux, % C build-up, soil C balance and crop productivity in a tropical dryland rice-barley-summer fallow agroecosystem. Addition of LQR singly resulted in high probability of C retention capacity compared to other treatments, however lower levels of soil C build-up, and crop productivity was observed. On the other hand, although in HQR treatment the C balance approached almost unity, the C build-up and crop productivity was comparable to that of the LQR treatment. Combining the two inputs resulted in significant build-up of soil C and enhancement of crop productivity and also indicated high C sequestration capacity. It is concluded that for sequestration of C, the resource quality of the input i.e., the form of C, labile or recalcitrant, is more important than the absolute amount of C added to the soil through exogenous inputs.
