| In recent years,due to the adjustment of industrial structure and the decline of cotton prices,the original rape-cotton rotation pattern in Dongting Lake area has gradually decreased,while the rape-summer corn rotation pattern has been increasing.In order to rationalize the use of straw resources and reduce N fertilizer application,trials were conducted in 2019 and 2020 with corn Zhengdan 958 as the material,as well as three straw decomposing inoculant brands screened through the market.In 2019,in Mutangyuan Town,Taoyuan County,Hunan Province,two different N application levels[local conventional N application(N1),20%N reduction(N2)]and different straw decomposing inoculant[no application(T0),“Dahua”straw decomposing inoculant(T1),“Ningliang”straw decomposing inoculant(T2),“Jiuye”straw decomposing inoculant(T3)],and conducted a field trial to study the effects of different treatments on growth and developmental traits and yield,soil physicochemical properties and microbiological characteristics of summer corn.In 2020,we set up four different levels of nitrogen application[local conventional nitrogen application(N1),20%nitrogen reduction(N2),40%nitrogen reduction(N3),20%nitrogen increase(N0)]and applied“Jiuye”straw decomposing inoculant(T3)at the experimental site of Yunyuan experimental base of Hunan Agricultural University to conduct pot trials.The effects of different treatments on the chemical properties and microbiological characteristics of the soil were investigated.The suitable type of straw decomposing inoculant and the appropriate application level of nitrogen fertilizer were screened out.The main findings of this experiment were as follows.(1)Through the field trial in 2019 we can find that the application of straw decomposing inoculant can accelerate the growth and development process of summer corn;the application of rototiller improved the agronomic trait index and increased the leaf area index of summer corn,and the 20%nitrogen reduction had no significant effect on the growth and development index of summer corn,and even The effect of T3 treatment on the advancement of growth and development,the improvement of agronomic traits and leaf area index of summer corn was more significant.(2)In terms of dry matter accumulation and yield of summer corn,the highest dry matter accumulation of summer corn was achieved by N1 level with T2 treatment,which was 14342.89 kg/hm~2;the highest yield was achieved by N2 level with T3 treatment,which was 6922.94 kg/hm~2.Except for the T2 treatment,there was no significant effect of 20%N reduction on the dry matter accumulation of summer corn without straw decomposing inoculant or other straw decomposing inoculant treatments;at the same level of N application,the yields of summer corn in T1,T2 and T3 treatments were higher than those in T0 treatment,and the yields of T3 treatment increased by 4.51%and 10.71%under N1 and N2 treatments,which were the highest values.The application of straw decomposing inoculant was beneficial to improve the protein,soluble sugar and amino acid content of summer corn kernels,and the reasonable nitrogen reduction increased the soluble sugar content of summer corn kernels,but would reduce the protein and free amino acid content and improve the quality of summer corn kernels,of which T2 and T3 straw decomposing inoculant treatments all improved significantly more than T1 straw decomposing inoculant.(3)In terms of soil chemical properties,in the 2019 field trial it was shown that the full amount of oilseed rape straw returned to the field with straw decomposing inoculant could effectively increase soil p H,soil organic matter,total nitrogen,fast-acting phosphorus and fast-acting potassium.The pot experiment in 2020 showed that within a reasonable range of N application,increasing N fertilizer application could improve soil p H,organic matter,total N,alkaline nitrogen,total phosphorus and fast-acting potassium content,but excessive N application would lead to soil nutrient imbalance,resulting in the decrease of each index.The differences between N2 and N1 N application levels were not significant or increased,while N3 application level significantly decreased soil alkaline nitrogen and total phosphorus;therefore,we considered N2 application level as the optimal N application level under this test condition.(4)From the perspective of soil microbiological characteristics,in the 2019 field trial,we found that the full amount of oilseed rape straw returned to the field with straw decomposing inoculant increased soil microbiological carbon and nitrogen contents,and significantly enhanced soil urease,catalase,sucrase and cellulase activities,among which the enhancement of soil microbiological and enzyme activities with T3 straw decomposing inoculant was the most significant;in the 2020 pot trial,the soil microbiological characteristics between N1.Therefore,considering the environmental benefits,the level of N2 application did not reduce most of the indicators of soil microbiological characteristics,but also reduced the amount of N fertilizer application and reduced the surface source pollution of the environment,which is the best level of N application.It can be seen from the two-year trial that the application of straw decomposing inoculant accelerated the decomposition of rape straw under the condition of returning rape straw to the field,which provided nutrients and microorganisms to the soil and accelerated the growth and development process of summer corn,improve the agronomic traits and quality,increase the leaf area index and dry matter accumulation,increase the yield of summer corn,improve the soil p H,increase the soil nutrient content,improve the microbial quantity carbon and nitrogen content,and enhance the soil enzyme activity;the appropriate application level of N can provide A suitable amount of nitrogen application can provide a good growth and development environment for crop growth and development,and can effectively supplement soil nitrogen.Within the reasonable range of nitrogen application,the increase of nitrogen fertilizer application can improve soil fertility,improve soil quality,increase microbial biomass and enhance soil enzyme activity.In conclusion,we can choose the control technology of 20%reduction of nitrogen application(N2)and application of“Jiuye”straw decomposing inoculant(T3)for summer corn production under summer corn-oilseed rape rotation pattern in Dongting Lake area,and this is the optimal combination of rototiller and nitrogen application derived from this experiment. |
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