| At present,the amount of fertilizer used by farmers is large,and the amount of organic fertilizer and straw returned to the field is small,the paddy water mixing process increases soil bulk density,and reduces soil fertility.In response to the above problems,this study set up a pot experiment(R0: conventional fertilization+ dry and wet alternate;R: conventional fertilization + straw returning + dry and wet alternate;RP: conventional fertilization + straw returning + alkaline fertilizer + dry and wet alternae;RI: Conventional fertilization + straw returning + long-term flooding)and field trials(control: only applying chemical fertilizer + water agitating pulp;conventional fertilization: straw returning to field + water agitating pulp;OPT1: straw returning to field + horizontally OPT 2: Straw buried deep into the field + flat ground;OPT 3: Reduce the amount of spike nitrogen fertilizer 10 kg·hm-2 based on OPT1,and apply alkaline fertilizer.Determine the content of soil reducing substances,plant dry matter and nutrient accumulation,soil fertility,rice yield and partial factor productivity of applied nitrogen,to clarify the effects of different tillage and fertilization modes on soil reductive material accumulation,soil fertility and rice yield,in order to provide technical support for the fertilization of rice fields in cold fields.The main results of the test are as follows:1.The fertilization model based on straw returning with fertilizers significantly increased the content of reducing substances in the soil,inhibited the growth of rice in the early stage,and reduced the accumulation of reducing substances in the field.When the rice was transplanted for 27 days,the straw was in the period of rapid decomposing,and the accumulation of reducing substances was the highest.Compared with R0 treatment,the total amount of soil reducing substances under R,RP and RI treatment increased significantl y by 91.76%,105.64% and 130.57%.The ferrous ion content increased significantly by 8.64 %,6.78 %and 19.49%;divalent manganese ion content increased significantly by 9.32 %,12.62% and 22.76%.At 42 days after transplanting,the total amount of reducing substances,ferrous ion content and divalent manganese ion content decreased by 58.64%-71.70%,37.70%-51.14% and 39.96%-45.99%,respectively,compared with 27 d when transplanted.At 42 days after transplanting,the total amount of reducing substances,ferrous ion content and divalent manganese ion content decreased by 58.64%-71.70%,37.70%-51.14% and 39.96%-45.99%,respectively,compared with 27 d when transplanted.At 42d-87 d after transplanting,the accumulation of reducing substances in R0 、 R and RP treatmentswas similar,RI treatment was still significantly higher than other treatments.The amount of reduced substance accumulated in the RP treatment was not significantly reduced.In the early stage of straw decomposing,the accumulation of reducing substances in the soil was higher,.The dry matter accumulation of rice decreased by 19.65%-43.51%,but the dry matter accumulation of rice in each treatment stage during the mature period.2.The effect of straw returning to the field with fertilizer application for fertilization for one year has little effect on soil physical and chemical properties.Treatment for two years can improve soil fertility.Compared with the R0 F treatment,the horizontal combination of straw returning to the field reduced the soil bulk density by an average of 4.92%.The soil organic matter content of straw returning and chemical fertilizer application treatment increased significantly by 5.16%-8.12%,.Compared with the initial value of soil organic matter content,the average annual increase of straw returning and chemical fertilizer applicat ion treatment increased by 1.37 g·kg-1.The initial available phosphorus content of R0 F treatment soil was higher than other treatments,but after two years of experimentation,the gap between soil available phosphorus content and R0 F treatment was reduced,.The content of available potassium in so il treated with straw returning and fertilizer application was 4.55%-11.47% higher than that of R0 F treatment.Compared with the initial available potassium content of soil,the average available potassium content of R0 F treatment decreased by 3.71 mg·kg-1 per year,and the average annual increase of straw returning and chemical fertilizer application was 14.26 mg·kg-1.3.For two consecutive years,the combination of chemical fertilizer and straw can promote the absorption of rice nutrients and increase t he accumulation of dry matter and yield..In 2017,there was no significant difference in nutrient uptake 、dry matter accumulation and yield between every treatments;In the 2018 rice maturity period,compared with ROF,the dry matter accumulation of OPT2 and OPT3 treatment increased by 7.40% and 3.53%,respectively;the nitrogen accumulation increased significantly by 32.87% and 14.48%;the potassium accumulation increased significantly by 8.25% and 8.82.%;the yield increased significantly by 0.43 and 0.49 t·hm-2;the nitrogen partial productivity increased significantly by 4.75% and 16.53%.In summary,the cultivation method of flat burying combined with straw returning and chemical fertilizer can ensure a good soil structure,and the application of cal cium-magnesium-phosphorus fertilizer in straw returning can improve soil fertility and rice yield.After the straw is returned to the field,the dry-wet alternate irrigation method can alleviate the inhibitory effect of reducing substances on rice growth. |
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