Estimating carbon fixation potential of fallow weeds in rice cropping systems

Abstract Fallow weeds are more and more common in Chinese rice cropping systems, but are always excluded in studies of vegetative carbon (C) sinks. This study aimed to evaluate the C fixation potential of fallow weeds in rice cropping systems. A six-region, two-year on-farm investigation and a three-year tillage experiment were conducted to estimate C fixation in fallow weeds in rice cropping systems. The on-farm investigation showed that the average mean C fixation in fallow weeds across six regions and two years reached 112 g m–2. The tillage experiment indicated that no-tillage practices increased C fixation in fallow weeds by 80% on average as compared with conventional tillage. The results of this study not only contribute to an understanding of C fixation potential of fallow weeds in rice cropping systems, but also provide a reference for including fallow weeds in the estimation of vegetative C sink. Further investigations are required to determine the effect of C input from fallow weeds on C balance of rice paddies in order to comprehensively evaluate the role of fallow weeds in C cycling in rice cropping systems.