| The decomposition process of straw after returning to the field is prone to produce reducing substances causing toxicity and affecting rice growth.Previous studies have focused on the southern dry and water rotation areas,while studies related to the effects of rice straw return to the field on soil reducing substances and rice growth in northern rice fields are relatively limited.pot trials were conducted in 2021-2022 on sandy loam(S1)and chalky loam(S2)soils,simulating four straw return amounts,with full straw return under no straw return(R0),low(RL)medium(RM)and high(RH)yields A total of 8 treatments were used.The total amount of soil reducing substances,Eh,ferrous ions,manganese ions and ammonium nitrogen content,rice root length,root dry weight,root vigor,tillering,dry matter accumulation,yield and composition,soil fertility at maturity,and soil bacterial community diversity were measured to study the formation of reducing substances and its relationship with rice growth after rice straw was returned to the field under different soils,in order to provide a theoretical basis for the scientific return of rice straw to the field.The main results are as follows The main research results are as follows:(1)The Eh of the soil was significantly reduced and the amount of reducing substances increased after straw return,and the reducing substances of S2 were higher than those of S1.Compared with the control,the total reducing substances,Fe and Mn of the straw return treatment on S1 soil increased by 8.36%-199.64%,1.43%-160.03%and 8.43%-57.68%by 035,0-35 and 0-45 days after transplanting,respectively,and the corresponding indicators on S2 soil increased by 2.95%-163.61%,0.77%-19.74%and 3.28%by 0-56,0-35 and 0-45 days after transplanting.57.68%,while the corresponding indicators for S2 soil increased by 2.95%-163.61%,0.77%-19.74%and 3.28%-64.96%until 0-56,0-35 and 0-45 days after transplanting.There was an increasing trend of total reducing substances,Fe and Mn with increasing amount of straw returned to the field.(2)The soil ammonium nitrogen content increased with increasing amount of return,significantly increasing the soil ammonium nitrogen content by 10.79%-351.53%from 0-56 days after transplanting.Straw return significantly reduced soil pH,and straw return significantly reduced the pH of S1 and S2 soils by 0.11-0.12 and 0.11-0.13 units,respectively.The effect of straw return to the field on soil alkaline soluble nitrogen and fast-acting phosphorus was not significant,soil alkaline soluble nitrogen was significantly higher under S2 soil than S1,and fast-acting phosphorus was higher in S1 than S2 in 2021.straw return to the field significantly increased soil fast-acting potassium by 5.53%-76.11%,and straw return to the field significantly increased soil organic matter by 2.13%-5.39%,with the increase of straw return to the field,soil fast-acting potassium in RH treatment and organic matter content of the RH treatment was 16.40%-61.93%and 1.27%-3.09%higher than that of the RL treatment,respectively.(3)Straw return favored the enrichment of Proteobacteria,Acidobacteria,and Chloroflexi,and promoted soil nitrogen cycling.Straw return increased the diversity of both soil bacterial communities,but not significantly,and RH treatment increased the enrichment of soil bacterial communities,and this effect was more pronounced on chalk loam soils.(4)Tillering stage and jointing stage decreased root dry weight by 15.06%to 45.80%.Tillering stage and jointing stage decreased root activity significantly under S1 soil,RL and RM increased root activity at jointing stage and RH decreased root activity on S2 soil.The number of tillers and dry matter accumulation decreased by 7.23%-48.44%and 3.59%-43.57%during the rice growth period after straw returning.RL and RM treatments did not significantly reduce rice yield in the second year,while RH treatments significantly reduced rice yield.Straw return significantly reduced nitrogen accumulation at the nodulation stage of rice under both soils by 12.43%-35.12%and increased nitrogen accumulation at the tasseling stage of rice under S1 soil by 6.74%-16.14%.Straw return significantly reduced the accumulation of phosphorus at the nodulation stage of rice under both soils by 16.22%47.13%,the RH treatment at the maturity stage of rice under S1 soil was significantly lower than the other treatments by 7.26%-17.48%,and the straw return treatment at the maturity stage of rice under S2 soil was significantly lower than the control by 3.57%-16.14%.Straw return significantly reduced the potassium accumulation in rice at nodulation under both soils in the first year by 19.67%-34.19%,and the straw return treatment at maturity under S2 soil significantly reduced the potassium accumulation in rice under 7.20%-22.23%. |
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