Abstract
When addressing water shortage in rice production, we need to consider the influence of water-saving irrigation methods on soil organic carbon stocks (SOC). A typical rice–rapeseed rotation was irrigated using 3 different strategies in rice growing season over a 3 year period: continuous flooding (CF), alternate wetting and drying irrigation (AWD), and rain-fed with irrigation only during drought periods (RFL). Soil samples were separated into fractions of different stability using sequentially fractionation methods. Compared with CF, AWD had no influence on C concentrations in physicochemically protected particulate organic matter in microaggregates (iPOM) at the 0–20 cm soil depth; however, it significantly increased the iPOM percentage in the bulk soil mass at the 5–10 cm soil depth. The RFL method lowered C stocks in iPOM at 0–20 cm soil depth, in comparison with CF and AWD, which was mainly due to its significant reduction in C concentrations in iPOM and the iPOM proportion in the bulk soil mass. The different water regimes had no effect on C stocks protected in silt and clay in microaggregates and unprotected free light POM. However, when considering the whole soil profile (0–20 cm), RFL significantly decreased total SOC stock, whereas there was no difference between CF and AWD. A moderate reduction in irrigation water under AWD strategy had little impact on SOC pools, thus, it could be considered an alternative water regime in balancing saving water and maintaining SOC stability.
Published Version
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