Impacts of Winter Planting Patterns on Soil Heavy Metal Content and Grain Quality in Late Rice in Double Cropping Rice Area

Abstract

On the basis of six-year fixed-location experiments in paddy fields, analysis was made on the impacts of different win-ter cropping patterns on soil heavy metal content, heavy metal content in different parts of late rice and late rice grain quality in double rice cropping area. The winter cropping patterns were ryegrass and double cropping rice (T1), Chinese milk vetch and double cropping rice (T2), rape and double cropping rice (T3), potato and double cropping rice (T4), fallow and double cropping rice (CK). The results showed that compared with the CK, the soil heavy metal content was affected by T1, T2, T3, T4 to some extent, the soil As content was decreased by T1, the soil Cd, Hg, As contents were decreased by T2, the soil Cd and Hg contents were decreased by T3, soil Pb and Hg contents were decreased by T4, but soil Hg content was increased by T1, soil As content was increased by T3, and the soil Cd, As contents were increased by T4, respectively. The distribution of heavy metal content in different parts of late rice was rootstem and leavesbrown rice. Meanwhile, the Cd, Pb, Hg, As contents in late rice root with different winter cropping patterns were significantly lower than those in CK. But the Cd contents in stem and leaves were in-creased. The Pb, Hg, As contents of stem and leaves were instability. And the Cd, Pb contents in brown rice were decreased by T1, T2, T3. The brown rice rate, head milled ratio, gel consistency and amylose content of late rice were increased by different winter cropping patterns, but the percentage of chalky rice and chalkiness were decreased. Meanwhile, the grain yield of late rice were increased under four winter cropping patterns conditions, and the yield of T4 increased by 17.52% compared with the CK. The experiments indicated that the soil heavy metal pollution were decreased to some extent by four winter cropping patterns, the Cd and Pb contents in brown rice were decreased, and the grain quality and grain yield of later rice were ultimately improved.