Changes Of Soil Available Nitrogen And Microorganism Under Different Cultivation And Management Modes Of Rice Wheat Rotation

The subjects of this experiment are rice and wheat.In the experiment,conventional japonica rice Wuyunjing 24 and indica japonica hybrid rice Yongyou 2640 were used as the test materials.The cultivation methods were as follows:A:nitrogen blank(no application of N fertilizer,the same as conventional fertilization),B:local conventional fertilization(300 n),B:nitrogen reduction(270 N.Nitrogen application amount decreased by 10%compared with conventional fertilization,C:nitrogen reduction and density increase(increased transplanting density by 20%compared with nitrogen reduction treatment),D:precision irrigation(increased precision irrigation compared with nitrogen reduction and density increase),e:increased cake fertilizer(increased cake fertilizer compared with conventional fertilization),F:increased silicon zinc fertilizer(increased silicon zinc fertilizer compared with conventional fertilization),F:deep cultivation(increased soil compared with precision irrigation)The soil turns deep.At different growth stages of rice,soil layers of 0-5cm,5-10cm and 10-20cm were collected and the content of available nitrogen was measured.The distribution of soil total nitrogen,organic matter,alkali hydrolyzed nitrogen,nitrate nitrogen,ammonium nitrogen,available phosphorus,available potassium and microorganism in the 1-meter section of rice at maturity were studied.Yangmai 16 and Yangmai 20 were used as test materials.The cultivation methods were as follows:A:nitrogen blank(0 N),B:local conventional(225 n),B:nitrogen reduction(200 N)N),C:density and nitrogen reduction,D:nitrogen fertilizer synergist,e:cake fertilizer,F:medium and micro fertilizer,F:deep turning of soil.The samples of 0-5cm,5-10cm and 10-20cm were collected in different growth periods of wheat in 2019 to determine the content of soil available nitrogen.The main results are as follows:1.Effect of different cultivation measures on available nitrogen in paddy soil1.Effect of different cultivation measures on available nitrogen in paddy soilIn the 8 cultivation models studied in this experiment,the content of nitrate nitrogen and ammonium nitrogen in different soils treated with blank control were lower,and farmers'conventional fertilization and treatment of increasing silicon zinc fertilizer and deep ploughing cultivation could effectively improve the content of quick nitrogen in soil.In the different growth stages of rice,the content of available nitrogen was relatively high in the early stage of rice growth,while in the late stage of rice growth,the content of nitrate nitrogen in each treatment was relatively low,and there was no significant difference between the treatments.For ammonium nitrogen,there was significant difference between rice tillering stage and other stages.2.Effect of different cultivation measures on soil available nitrogen of WheatFor the nutrient content of available nitrogen in wheat field,the residual amount of ammonium nitrogen in the soil is significantly lower than that of nitrate nitrogen,especially in 0-5cm soil layer.For the change of the nutrient content of the quick effect nitrogen in the same soil layer,the nitrate nutrient content in the soil corresponding to the treatment of micro fertilizer and the treatment of deep ploughing is relatively high,while the change rule of the ammonium nitrogen in each treatment is not obvious,there is a certain amount of nitrogen accumulation in the treatment of micro fertilizer and the treatment of deep ploughing.In the growth period of wheat,for the content of residual nitrate nitrogen in the soil,the nutrient content of each treatment is higher in the overwintering period of wheat,and for the ammonium nitrogen,the nutrient content is higher in the mature period of wheat.3.Effect of different cultivation measures on nutrient content of rice soil profileAccording to the nutrient situation of rice profile,for the content of total nitrogen and available nitrogen,the residual amount of nitrogen blank and nitrogen reduction in the soil was relatively low,and the relative nitrogen nutrient content of cake fertilizer,silicon zinc fertilizer and deep cultivation was relatively high.With the increase of soil depth,except for available phosphorus in 2019,the nutrient content of other treatments decreased with the increase of soil layer,and the nutrient content of surface soil was significantly higher than that of other layers.4.Effect of different cultivation measures on microbial changeFor the heading stage of paddy soil,the bacterial richness in the mature stage will be reduced.In the two periods,Proteobacteria,chloroflexa,acidobacteria and actinobacteria were the most abundant.The number of unique OTUs of soil samples treated in the two periods was similar.The diversity of soil bacterial community was not obviously changed by different cultivation measures,and the anaerolineaceae in treatment B and f accounted for a high proportion of the most important bacterial families in all treatment samples.The improvement of cultivation measures may have a greater impact on the non major bacterial groups in the soil.The correlation analysis did not find that the above-mentioned phylum was related to soil available nitrogen,which might be more affected by other cultivation measures.