| In the present study,the paddy fields with moderate cadmium pollution were selected,the early rice variety Lu Liangyou 996 and the Late rice variety H You 518 was used as the test material to explore the effects of bio-char and water management coupling on the related factors of soil cadmium bio-availability and cadmium absorption,migration and accumulation in late rice were studied through field split-plot experiments.Four water management methods including pre-dry and post-flood(W1),pre-flood and post-dry(W2),long-term flood(W3)and conventional water management(W4)were used as the main treatments,and bio-char with four gradients(C1-5t/hm~2,C2-7.5t/hm~2,C3-10t/hm~2,C4-0t/hm~2)was used as the secondary treatment.The results showed that:(1)Under the coupling treatment of biochar and water management,the p H value of soil increased,with the rising range of 0.65-1.37,and the rising range of W3-C3 was the largest,reaching 1.37.Under the same water management condition,the p H value of soil increased with the increase of carbon application,and the p H value tended to be neutral;under the coupling treatment of water and carbon,the content of soil organic matter increased,with the increasing range of 1.3-6.1 g/kg In the same water management mode,different carbon application levels had different effects on soil organic matter,and there was no obvious rule.(2)The effect of water carbon coupling on soil available cadmium content was significant.Under different treatments,soil available cadmium content decreased in the range of 0.01-0.17mg/kg.The treatment with the lowest available cadmium content was W3-C2,which was 42.75%lower than CK(conventional water management+no carbon application).(3)The effect of water carbon coupling on the yield and yield composition of early and late rice was small,and did not show obvious regularity.The difference between the treatments was not obvious.The actual yield of W1-C1 was the highest in early rice,with an increase of 22.42%compared with CK,and it was later The highest yield was W2-C3,which was 42.55%higher than CK.(4)Among the early rice treatments,the W2-C3 brown rice had the lowest cadmium content,followed by W3-C3.Compared with CK,the W2-C3 brown rice cadmium content decreased by 57.78%,and the content was 0.19mg/kg;among the late rice treatments,W3-C3 had the most obvious effect on reducing the cadmium content of brown rice.Compared with CK,the cadmium content in brown rice was reduced by 59.10%,and the content was 0.18mg/kg.In the same main treatment,the content of cadmium in all organs of early and late rice at the mature stage showed a downward trend with the increase of carbon application.(5)Water-carbon coupling has a significant effect on the accumulation of cadmium in various parts of early and late rice during maturity.The accumulation of cadmium in early rice during maturity is significantly reduced,and the lowest accumulation is W1-C3.Compared with CK,the decrease is 57.38%;The accumulation of cadmium in brown rice of late rice during maturity was significantly reduced,and the treatment with the lowest accumulation was W3-C3,which decreased by 53.44%compared with CK.(6)Water-carbon coupling can weaken the transport capacity of cadmium between rice organs,but the effect is not significant.Compared with CK,the treatment of the cadmium absorption of early rice from the root to brown rice,and from the stem to the brown rice decreased the most.It is W4-C2,with a decrease of 45.26%and 37.13%,respectively;the treatments for the transfer coefficient of cadmium absorbed by late rice from roots to brown rice,and from stems and leaves to brown rice decreased the most by W3-C2 and W3-C3,respectively.38.48%,24.31%.In conclusion,long-term flooding coupled with carbon application rate of 10t/hm~2 has a good effect on cadmium reduction,which can effectively inhibit the absorption,migration and accumulation of cadmium in rice.It is a recommended way to reduce cadmium. |
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