Study On The Correlationship Between Straw Returning Modes And Soil Reductibility And Fertility In Paddy Fields

Straw returning can improve soil fertility and reduce environmental pollution,whereas the accumulation of reducing substances in rice fields under the condition of straw returning can also be toxic to rice growth.Hence,research on ways to exert the positive effect of straw returning and reduce its negative effect is of great significance.In view of that,pot experiments have been conducted during the 2021-2022 period to study the effects of straw returning and no pulping on soil reducing substances,soil fertility and rice yield,so as to provide theoretical basis and technical support for scientific and effective straw returning.In the experiments,comparison soil samples,paddy soil(SR0)without straws returned to the field and paddy soil with straw returning for four consecutive years(SR4)were selected and treated respectively in three returning modes,namely,non straw returning(CF),straw returning without stirring slurry(RF)and straw returning with stirring slurry(RFT).The main research findings are as follows:After straw returned to the field,the reductive substances in the soil were significantly increased.The alternative dry and wet irrigation with no pudding could reduce the soil redox potential,also the production of reductive substances.In SR0 and SR4 soil,there was no significant difference in the total amount of reductive substances and redox potential(p>0.05),and the soil returned for many years had no cumulative effect on the content of reducing substances.The total amount of reducing substances in RF and RFT treatment in 2021 was 6.82%-76.65% and 8.57%-176.57% higher than that in CF treatment,respectively,and 11.02%-106.72% and 25.15%-186.23% higher than that in 2022,respectively.The RF treatment had a lower reduced iron content than the RFT treatment,and the RF treatment had a 2.9%-11.6% lower reduced manganese content than the RFT treatment.The alternate dry and wet treatment is beneficial in reducing the reduced manganese ions.The soil fertility was improved after straw returned.The content of organic matter,available P,available K,and bacterial community in the SR4 soil was higher than in the SR0 soil without straw returning.The organic matter,alkali hydrolyzable nitrogen,available P,and available K of RF treatment were 0.64%-0.65%,2.71%-7.19%,2.64%-3.10%,and 15.60%-19.10% higher than those of CF treatment respectively.The relative abundance of Bacteroides and Chloroflexi in SR4 soil was higher than in SR0 soil.The comprehensive fertility index of SR4 soil was 14.23% higher than that of SR0 soil.Under the condition of straw returning,the fertility index of RF treatment was0.69%-2.87% higher than that of RFT treatment.Returned straw inhibited rice root growth at tillering stage.At the jointing stage,the root length,average diameter,root tip number and root oxidation capacity of straw returning to the field were significantly increased(p<0.05).The rice yield of the RF treatment was higher than that of RFT treatment.The rice yield of RF treatment was3.90%-5.40% higher than that of RFT treatment in 2021,and 8.09%-9.59% higher in2022.In summary,straw return to the field increased reducing substance,alternate wet and dry irrigation and RF treatment reduced soil reducing substance compared to RFT treatment,and soil returned to the field for many years increased soil organic matter,available P and available K content,improved soil fertility index and promoted rice field productivity.At the same time there was no increase in the total amount of soil reducing substances,and the positive effect of continuous years of straw return to the soil was significant,while the negative effect was not increase.