| The hilly area of the Loess Plateau is an important grain producing area in China,and it is also the area with the most fragile ecological environment and the most serious soil erosion in China.In order to solve the problems of poor structure and low fertility of the newly cultivated land by the"Gully land consolidation"project on the Loess Plateau,in this study,field experiments were carried out at the Ansai Station Shiyaogou Sichuan Test Site,Institute of Soil and Water Conservation,Ministry of Water Resources,Chinese Academy of Sciences from May to October in 2019 and 2020.A total of 5 treatments were set up:organic fertilizer+chemical fertilizer（ON）,crushed straw+chemical fertilizer（FN）,50%organic fertilizer+50%crushed straw+chemical fertilizer（OFN）,chemical fertilizer（N）and no fertilizer（CK）.I mainly studies the effects of different organic materials on soil aggregates,soil carbon and nitrogen and the growth of spring maize,evaluates and analyzes the soil fertility status of different organic materials returned to the field,and selects the plough layer（0-20 cm）soil maturation and fertilization technology suitable for newly cultivated land in northern Shaanxi.The main conclusions are as follows:（1）Fertilization can reduce the proportion of soil microaggregates,and mainly increase the proportion of>5 mm mechanical aggregates and 0.25～0.5 mm water-stable aggregates in the surface layer.The ON and OFN treatments with the addition of organic fertilizers were more effective than the single application of chemical fertilizers in improving the mechanical aggregates with a fraction of>5 mm and the water-stable aggregates with a fraction of0.25～0.5 mm in the 0-20 cm soil layer.Compared with the single application of chemical fertilizer,the MWD,GMD and R0.25of the soil treated with organic materials were significantly improved,and the ON treatment had the best effect on the improvement of the aggregate stability index.But there was no significant difference between FN and N treatment in improving the stability of soil mechanical aggregates.Secondly,the stability of soil aggregates increased with the increase of soil organic carbon content,and the relevant indicators were all significantly positively correlated with soil organic carbon content.（2）The return of organic materials to the field effectively increased the soil organic carbon（SOC）and total nitrogen（TN）contents in the plough layer.The content of SOC and TN in water-stable aggregates increased with the decrease of aggregates size.Soil SOC was mainly distributed in the aggregates of<0.25 mm size and 0.25～0.5 mm size,and soil TN was most distributed in<0.25 mm size.Compared with the single application of chemical fertilizer,the return of organic materials to the field can significantly increase the SOC content of each size of water-stable aggregates,decreased the SOC contribution rate of the 0-20 cm soil layer<0.25 mm,and significantly increased the 0.25～0.5 mm SOC contribution of the 0-20 cm soil layer.Compared with other treatments,the ON treatment has the best improvement effect.After 80 days of combined application of organic materials,the nitrate nitrogen content in the 0-100 cm soil layer higher than that of the single application of chemical fertilizers.Organic fertilizer can increase soil surface moisture,and ON and OFN treatments significantly increased the soil moisture content in the 0-20 cm soil layer from the three-leaf stage to the six-leaf stage.The addition of straw was beneficial to the accumulation of deep soil moisture,and the soil moisture content of the 60-100 cm soil layer in the FN treatment was higher than that in the N treatment at the tasseling and mature stages.The application of organic materials can increase the soil water storage capacity of 0-100 cm,and the average water storage capacity of the FN treatment during the crop growth period was increased by 2.8%compared with the CK.There was no significant difference in soil water storage between treatments in different periods.（3）Compared with single application of chemical fertilizers,the return of organic materials to the field has no advantages in improving the components of yield,and the return of straw to the field is not conducive to the rapid increase of crop yield.Combined application of organic fertilizer can improve crop yield and WUE,and ON treatment has the best effect of increasing yield and improving crop water use efficiency.The total nitrogen content in grains of single application of chemical fertilizer was higher than that of organic material treatment,but in terms of biomass,it was lower than that of ON treatment.The stem and leaf biomass of OFN treatment increased,but there was no significant difference between total biomass and N treatment.Compared with the CK treatment,the nitrogen accumulation in each part of the fertilization treatment at the mature stage was significantly increased.The ON treatment increased the total nitrogen accumulation of maize by 8.8%compared with the N treatment,and the grain nitrogen accumulation increased by 6.7%compared with the N treatment.However,the FN and OFN treatments Grain nitrogen and total nitrogen accumulation in grains were not as good as those in N treatment.ON treatment significantly increased AEN,REN and PFPN by 20.2%,12.5%??and 12.7%,respectively.There was no significant difference in nitrogen utilization between OFN treatment and N treatment.The value of FN in the nitrogen utilization index was relatively small,in this study,the amount of nitrogen accumulated in crops with straw returning and chemical fertilizer application was not as good as that in organic fertilizer and chemical fertilizer application.In conclusion,with 2 years of input of organic materials,it was finally found that replacing50%of chemical fertilizers with organic fertilizers had the best effect on improving soil carbon and nitrogen,aggregates and yield.Provide technical support for the efficient and sustainable utilization of newly cultivated land in the Loess Plateau and the consolidation of ecological environment construction achievements. |
PDF Full Text Request