| Focus on the problems of low yield of crops caused by shallow plough layer,uplift of plough bottom and soil nutrient deficiency,the potato and spring wheat were the research objects.Different tillage methods(ploughing 15 cm(C15),ploughing 30 cm(C30),subsoiling 30 cm(S30),subsoiling 40 cm(S40),subsoiling 50 cm(S50)and so on were set up in the dryland area of south Ningxia from April 2019 to July 2020.The effects of different tillage methods on soil nutrient,enzyme activity,microbial biomass carbon and nitrogen content,crop yield and economic benefits were studied in the field experiment,and so as to screen out the soil tillage method of stable yield in dry area,which could provide theoretical reference and technical support for maintaining soil fertility and high yield cultivation of crops in this area.The main results of two-year experiment are as follows:(1)The soil organic matter content in 0-60 cm layer with S30 and S50 was the best in different tillage methods,the soil total nitrogen content with S40 was the best,the soil total phosphorus content with C15 was the best in heading stage of wheat,and soil total phosphorus content with S50 was the best in harvest period.The content of soil total potassium with S30 was best,the content of alkali nitrogen with S40 was best,and the available phosphorus content with S40 and S30 was the best.It could be seen that the subsoiling treatments was better than the ploughing treatment in improving soil fertility,and the S30 and S40 treatments were the best.(2)Subsoiling tillage could increase the enzyme activity of soil enzyme in 0-60 cm layer.The soil urease activity with S30 and S50 was the best in the potato harvest period,the soil sucrase and catalase activities with S40 and S50 were the best,and soil alkaline phosphatase with S30 and S40 was the best.The activities of soil urease,sucrase,catalase,and alkaline phosphatase with S40 was the best in harvest stage of spring wheat.(3)The soil microbial biomass carbon and nitrogen content in 0-60 cm layer during crop harvest period were different under different tillage methods.The soil microbial carbon content in 0-20 cm layer under each treatment in potato field from highest to lowest was:S50>S40>S30>C30>C15.The soil microbial carbon content with S40 in 20-60 cm layer had the maximum value.The soil microbial carbon content in 0-20 cm layer under each treatment in wheat field was S40>S50>S30>C30>C15,while the order of the differences in microbial carbon content at 20-60 cm layer was S30>S40>S50>C30>C15.The soil microbial nitrogen content in 0-20cm layer in potato field from highest to lowest was:C15>C30>S30>S40>S50,and C15>S30>S50>C30>S40 in 20-40 cm layer,and C30>S50>C15>S30>S40 in 40-60 cm layer,respectively.The soil microbial nitrogen content in 0-20 cm layer in wheat field from highest to lowest was C15>S30>S50>C30>S40,and S50>C15>S30>C30>S40 in 20-40 cm layer,and S30>S50>C15>C30>S40 in 40-60 cm layer,respectively.It could be seen that the soil microbial biomass carbon and nitrogen content under subsoiling treatments were significantly higher than that of the ploughing treatment.(4)The yield of potato from highest to lowest was:S40>S50>S30>C30>C15,and the potato yield of S40 treatment was the highest,which was 15.17%higher than that of C15.The net income of S40 treatment was the highest(28424.6 yuan/hm2),and the second was S50 treatment(27526.14 yuan/hm2),which was significantly increased by 18.91%and 15.16%compared with C15 treatment,respectively.The order of the differences in the spring wheat yield was S40>S50>S30>C30>C15,and the S40 treatment significantly increased the yield by 59.25%.The net income of S40 was the highest(10855.5 yuan/hm2),and S30 treatment(10714.4 yuan/hm2)was the second,which was 88.22%and 85.82%higher than that of C15 treatment.It could be seen that the yield and income of potato and wheat could be increased by subsoiling 40 cm.(5)Through the principal component analysis of potato and spring wheat yield and various soil chemical indexes,it was found that the key factors to promote potato yield under different tillage methods were soil available phosphorus,total nitrogen,catalase and microbial biomass carbon,while the key factors to promote spring wheat yield included soil available phosphorus,urease,sucrase,catalase,alkaline phosphatase and microbial biomass carbon.Through principal component analysis,it was found that subsoiling 40 cm had the best yield increasing effect.In conclusion,compared with the traditional ploughing 15cm,subsoiling tillage could improve soil fertility and increase the yield of potato and spring wheat.The best effect was subsoiling 40 cm,which was improved soil fertility and increase crop yield in dryland area of southern Ningxia. |
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