| Soil is an important part of the farmland ecosystem,and it is also an essential and important resource for agricultural production.The level of soil fertility will inevitably affect the growth and yield of crops,straw mulching to the field and rational fertilization are important ways to maintain and increase soil fertility.However,the improper utilization of straw and nitrogen fertilizer in the Guanzhong region is still widespread.In the long run,the soil fertility will inevitably be reduced.Therefore,it is of great significance to explore the scientific and rational straw mulching and nitrogen application methods to improve soil physical and chemical properties,maintain soil nutrient balance,and ensure the sustainable development of land productivity.Based on the current agricultural production status in Guanzhong region,this paper selects the wheat-maize planting system as the research object.Through the long-term positioning and re-split zone test,the main area is set with three straw returning levels(straw mulching: S,half straw mulching: HS,no straw mulching: NS),three nitrogen application levels were set in the subzone(full nitrogen application: F1,80% application of nitrogen: F0.8,no application of nitrogen: F0),and NSF0 was treated with CK.Through continuous multi-year positioning experiments,the effects of straw return and nitrogen application on the soil physical and chemical properties of five-year crops under the wheat-maize multiple cropping system in Guanzhong area of Shaanxi Province were analyzed,and the crop yield and economic benefits were selected to be suitable for Guanzhong.The best straw returning and fertilization combination model in the region lays the theoretical foundation for the rational use of agricultural waste,scientific fertility,and sustainable agricultural development.The main conclusions are as follows:(1)Straw mulching with nitrogen fertilizer is beneficial to the improvement of soil physical properties.Among them,the soil bulk density in the 0-10 cm soil layer of the five-season crops showed a decreasing trend with the increase of the straw returning amount.Under the condition that the straw returning amount was certain,the nitrogen application amount had no significant effect on the soil bulk density.The interaction between straw returning and nitrogen application can cause changes in soil bulk density.Soil bulk density of 0-10 cm and 10-20 cm soil layers under SF1 treatment in the five season crops was lower than that of CK.In the same treatment(SF1),the soil bulk density of 0-10 cm soil was smaller than that of the first season in the second season,while the soil density of the other 20-40 cm soil layer was larger than that of the first season in the second season,and the soil bulk density was changed during different years.The law is not obvious.In addition,the soil water content in crops during different growth periods differs greatly.With the increase of straw return and nitrogen application,the increase in average water content during the whole growth period of crops is also increasing.The average water content in the whole growth period of the five seasons crops showed that under the same nitrogen application level,the soil water content increased with the increase of straw returning amount.At the same level of straw return,the increase in soil water content increases with the increase of nitrogen application rate.(2)The application of nitrogen fertilizer with straw mulching can increase soil nutrient content and reserves.The application of straw and nitrogen fertilizer can significantly affect the content of soil organic carbon and available nutrients in wheat and corn.In 2016,the highest organic carbon content in 0-20 cm soil layers of wheat and corn was HSF1,which was 45.36% higher than CK and 57.89% higher than CK respectively.The rest was highest under SF1 treatment,which was 45.52% higher than CK(0-20 cm in 2015 corn).63.21%(2015 corn 20-40cm),63.97%(2016 wheat 20-40cm),65.14%(2016 corn 20-40cm),57.14%(2017 wheat 0-20cm)(2017 wheat 20-40cm),55.72%(2017 corn 0-20cm),117.84%(2017 corn 20-40cm);SF1 treatment is the highest in alkaline dissolved nitrogen,available phosphorus and available potassium.Organic carbon stocks,except 2016,had the highest HSF0.8 and the 2016 corn had the highest HSF1 treatment.All the other crops showed the highest SF1 treatment.The total nitrogen stocks were the highest in 2016 except that of wheat.The rest of the season crops showed the highest SF1 treatment;the total phosphorus reserves except the HSF0.8 of 2016 wheat and the SF0.8 of 2017 wheat were the highest among the other season crops.Soil fertility ratio(0-20cm/20-40cm)was the lowest under S×F interaction.(3)Straw mulching can reduce the pH of the soil when it is not returned to the straw,and nitrogen can also reduce the pH of the soil.At the beginning of the experiment(2015),SF1 and HSF1 were lower in 0-20 cm soil than in NSF1,SF1 and SF0.8 are lower than SF0,and SF1 is 4.19% lower than NSF0;In the 20-40 cm soil layer,SF1 and HSF1 were lower than NSF1,and HSF0.8 and NSF0.8 were lower than NSF0.At the end of the trial(2017),SF1 and HSF1 were lower in 0-20 cm soil layer than in NSF1,SF1 and SF0.8 are lower than SF0.SF1 and HSF1 in 20-40 cm soil layer are lower than NSF1,and NSF0.8 and SF0 are lower than NSF0.In addition,under the SF1 treatment,soil pH was also the same in 2017(0-20cm)in 2017,0.12%(20-40cm)lower in 2017 than in 2015,and 0.12(0-20cm)lower in 2017 than in 2015 under SF0.8 treatment.And 0.98%(20-40cm),we can see from the beginning of the experiment to the end of the test the same soil in the same soil pH the same or little difference,indicating that straw returning and nitrogen can adjust the p H of the soil to keep it in a certain range.(4)The application of straw mulching and nitrogen fertilizer can increase soil enzyme activity.The activity of soil catalase was the highest in 0-20 cm maize in 2016,and the rest was SF1 had the highest activity.Soil Alkaline Phosphatase Activity In addition to the 20-40 cm soil layer in 2016,the HSF1 treatment activity was the strongest,and the rest was the highest in SF1 treatment activity.Soil urease activity was highest except HSF1,which was the 20-40 cm wheat activity in 2016.The rest was SF1 with the highest activity.Soil invertase activity was the highest in SF1 treatment activity.(5)The maximum yield was obtained when the total amount of straw was applied to the field and the total amount of nitrogen fertilizer was applied,and the maximum benefit was obtained when the total amount of straw was returned to the field and 80% of nitrogen fertilizer was applied.Among them,the highest economic benefit for the 2016 and 2017 years was SF0.8,which was 60.86% and 67.83% higher than that of the control group NSF0.The comprehensive scores of different treatment factors in the winter wheat-summer corn multiple cropping system showed that wheat and corn had the highest comprehensive score under the treatment of straw total amount and total nitrogen fertilizer(SF1),indicating that the soil physicochemical properties were the best under this treatment,but From the perspective of economic benefits and green agriculture,the treatment of total straw and 80% nitrogen fertilizer is suitable for increasing the popularity of wheat-corn planting in the Guanzhong region. |
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