Abstract: With the vigorous promotion of straw returning technology, different straw returning methods have been widely applied in Northeast China. We examined the effects of straw returning on organic carbon in a saline-alkaline tillage soil, aiming to provide a scientific basis for the rational utilization of straw. We set up a field experiment with four treatments, including no straw application (CK), no-tillage + straw coverage (NTS), rotary tillage + straw (RTS), and deep tilling + straw (PTS). The results showed that straw returning significantly increased the contents of particulate organic matter (Fm-POM) in free microaggregates, particulate organic matter (mM-POM) in occluded microaggregates and organic carbon content of silt + clay (mM-SC) components in closed microaggregates in 0-20 cm soil layer. In 0-20 cm soil layer, RTS treatment had higher contents of coarse particulate organic matter (MA(c)POM), closed microaggregates (mM), mM-POM and mM-SC components, which improved the stability of organic carbon in topsoil. In the 20-40 cm soil layer, PTS treatment increased organic carbon contents in mM-POM and mM-SC fractions. Straw returning can be used as an effective measure to improve organic matter in saline-alkali soil.

Key words: aggregate, organic carbon fraction, straw return method,  , saline-alkaline dryland