| Based on the 7-year long term experiment at fixed site field, the farmland in the typical arid and semi-arid farming-pastoral zone was selected to study spatial variation characteristics of soil water content, temperature, bulk density, nutrient, soil microorganism and enzyme activity under different tillage methods, and based on this,(1) water utilization ratio under different tillage methods was analyzed;(2) optimum regression model of soil nutrient, soil enzyme and soil microorganism was established through the method of stepwise regression;(3) soil fertility quality under different tillage methods was evaluated by the method of factor analysis, and evaluation results were verified by corn yields;(4) economic benefits under different tillage method were analyzed. The results showed that:(1) In the 0～25cm soils, soil temperature of topsoil was the highest in the film mulching treatment in May and Jun, soil temperature was higher in the no-tillage and straw mulching treatments than that in the film mulching and plowing treatments in Jul, August and September.(2) In the 0～40cm soils, film mulching, no tillage and straw mulching treatments had obvious characteristics of water holding and water balance controlling. In the whole growth period of corn, soil water content changed smoothly with the variance range of 14.63%~17.87%, 9.81%~19.67% and 9.22%~14.91% respectively. Traditional plowing changed sharply with variance range of 10.69%~36.95%.Output and biomass water utilization ratio in the no-tillage, film mulching and straw mulching treatments were higher than that in the plowing treatment, which increased by 13.1%, 23.8% and 4.4%, 37.9%, 33.9% and 26.5% respectively.(3) Organic content after harvest in the no-tillage, straw mulching, film mulching and plowing treatments was higher by 18.83%, 5.78%, 12.53% and 5.97% respectively than that before sowing in the 0～20cm soils; In the 20～40cm soils, organic content after harvest was slightly lower than that before sowing in the straw mulching treatment, whereas other treatments were contrary. Soil total N before sowing in the no-tillage, straw mulching, film mulching and plowing treatments was higher by 16.86%, 8.82%, 36.60% and 23.18% in the 0～20cm soils respectively and 61.14%, 55.81%, 22.02% and 30.31% in the 20～40cm soils respectively than that after harvest; soil total P after harvest in the no-tillage, straw mulching, film mulching and plowing treatments was higher by 27.08%, 10.28%, 10.31% and 13.79% in the 0～20cm soils respectively than that before sowing; soil available N before sowing in the no-tillage, straw mulching, film mulching and plowing treatments was lower by 40.02%, 33.11%, 22.45% and 30.58% respectively than that after harvest; soil available P before sowing in the no-tillage, straw mulching, film mulching and plowing treatments was higher by 10.88%, 14.77%, 27.18% and 42.00% in the 0～20cm soils respectively than that after harvest; Not much changed for soil available K in all treatments before sowing and after harvest.N fertilizer utilization ratio was 1.38 and 1.67 higher in the no-tillage and film mulching treatments than that in the plowing treatment, but was very similar between the straw mulching treatment and the plowing treatment, and P fertilizer utilization ratio was 1.41 higher in the no-tillage treatment than that in the plowing treatment, yet was 1.13 and 1.6 lower in the film mulching and straw mulching treatments than that in the plowing treatment.(4) Under different tillage methods, the activity of phosphatase was significant higher in the SM and NT treatments than that in the CT and FM treatments in the 0～20cm soils; the activity of phosphatase was lowest in the SM treatment; the activity of sucrase was significant higher in the SM treatment than that in other treatments; the activity of phosphatase, urea and sucrase of 0～20cm soils were higher in the NT treatment; Enzyme activity of 40～60cm soils changed little in all treatments.The activity of catalase decreased in the SM treatment as depth increased in soil profiles, a tendency of firstly increase and then decrease in the NT treatment, almost unanimous under the CT and FM treatments in the 0～20cm and 20～40cm soils, and the activity of catalase in the CT treatment was greater below 40cm than that in the 0～40cm soils; Other enzyme activity decreased as depth increased, and delaminating was obvious in the NT and SM treatments but not obvious in the CT and FM treatments.(5) Under different tillage methods, the cont of all bacterial in the 0～20cm soils was significant higher in the CT and FM treatments than that in the CT and FM treatments, and no significant change among all bacterial seemed in the 20～40cm soils under different tillage methods, and there was almost no change in the 40～60cm soils. Three types of bacterial decreased as soil depth increased, and significant changes of microorganism of soil levels in the SM and NT treatments appeared, yet not in the CT and FM treatments.(6) Soil enzyme and fungus had a positive correlation with water content, yet a negative correlation with bulk density; the activity of phosphatase, urea and sucrase had a significant positive correlation with soil organic matter, total N, total P, nitrite N and available P; soil microorganism had a significant correlation with organic matter, yet not significant with other nutrients, catalase on the whole had a negative correlation with fungus; there was a positive correlation among the activity of phosphatase, urea activity and sucrase.(7) The no-tillage treatment had the strong potential ability of nutrient supply and higher organic content; organic and enzyme activity in the film mulching treatment was higher; organic content was lower in the plowing treatment so that it was not conductive to improve soil; disadvantages about the potential ability of nutrient supply, organic content and enzyme activity occurred in the straw mulching treatment. Considering soil fertility quality, the film mulching treatment was the best, and the straw mulching treatment was the worst, which suggested evaluation results were accordant to the output results.(8) The mean increased income ratio of output in the film mulching, no-tillage and straw mulching treatments was higher by 17.53%, 8.78% and 0.34% respectively than that in the traditional plowing treatment. However, as the labor costs increase with years, the film mulching treatment tends toward to be eliminated, and the no-tillage treatment will gradually become the first tillage measure for local people. |
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