| Chinese scientists have been carrying out a mass of research work about conservation tillage since that was introduced into China in 1960's. But most of the research work and demonstrations were done in arid or semiarid area in north China. And the main purpose of the work was to reduce wind-water erosion or ensure the normal yield of field crops. But there seldom was research in sub-humid area which was aim to increase the yield of field crops in condition of normal irrigation or decrease the irrigation. The rule of spatial and temporal distribution of soil nutrition and the response of crops was also lacked. So we carried out experiments from 2004 to 2006 in the agronomy research base of Shandong agricultural university. The experiment was conducted to explore the rule of nutrition changing in soil and the response of crops which was managed by conservation tillage in wheat-maize two crops one year farming system. After that, we evaluated the field ecosystem service of different conservation tillage by the way of ecological economics on the basis of data from experiments. So that we could choose a better one from all the treatments and make a more effective use of natural resource. At the same time, we wanted to provide scientific evidence to governments. The main results were as follows:1 In the farming system of wheat-maize two crops one year, rotary tillage or harrow tillage can be adopted as the substitute of conventional tillage in two or there years in which the aftereffect of conventional tillage can last. Sub soil tillage can also be used as an efficient management to break the plough sole. As soon as these three soil managements were applied, the straw of wheat and maize should be returned to the soil in order to promote the condition of soil health.The result showed that the soil bulk density in 0-20cm layer of harrow tillage or conventional tillage which was applied for two cycle of wheat-maize was less than 1.5 g/cm~3. Crops could grow properly. But the soil bulk density in 0-20cm layer of harrow tillage or conventional tillage is over 1.6g/cm3. Further more, the value directed to a higher one. Especially the bulk density of 10-20cm layer of zero tillage was over 1.5g/cm3 and presented an obvious direction to a higher value at which the root of crop could not growth well. On the contrary , the bulk density of subsoil tillage in different soil layer was under 1.55 g/cm3. Its value didn't change obviousely.2 In proper time, the soil in the treatment of rotary tillage, harrow tillage, subsoil tillage with straw present had sane pore structure and higher content of OM, TN, TP, microbial biomass carbon and active microbial biomass. But the conservation tillage practices stratified the soil nutrition. The nutrition index of deep soil layer was lower than that in conventional tillage. Although no harm was done to crop yield, the value of soil nutrition accumulation was decreased.Straw returning was helpful to create a moderate massiness of soil and decrease the range of soil bulk density increase. It was able to modify the condition of soil moisture and save more water in soil. Because straw returning had the ability of decreasing the evapotranspiration, the content of soil moisture and pondage was much higher that CK. The yield of was increased in this condition. Further more, straw returning could affect the temperature of surface soil layer. Straw returning could enhance the temperature of surface soil layer in the winter. But when the air temperature rises up in the stage of wheat regreening, the temperature of soil in straw returning treatment was lower than CK. From the anthesis to the stage of filling up, when the air temperature was high, the soil temperature of zero tillage is higher than any other treatment. The possible reason may be related to the over-small colony and lower utilization of PAR.In proper time of conservation tillage, Rotary tillage, harrow tillage, subsoil tillage combined with straw returning could increase the grain yield by average of .6%,10.6%,8.2% in two years. On the contrary, the grain yield of zero tillage was obviously lower than CK by an average of 7.1% in two years.Rotary tillage, harrow tillage, subsoil tillage combined with straw returning was helpful to enhance the rate of dry matter accumulation and prolong the time of active accumulation stage. That establishs the basis of high yield. The leaf area index and content of chlorophyll in flag leaf was kept at a high level, so that the wheat had higher photosynthesis and photochemistry efficiency. That was helpful to accumulation of photosynthate and enhancing the grain filling rate. It's an efficient way to increase the weight of grain. Because of the over-high bulk density of soil in zero tillage treatment, wheat in this treatment was obviously premature. So almost all of the testing indexes of zero tillage were at a lower level.The working quality of rotary tillage, harrow tillage and subsoil tillage was little lower than the demand of agricultural seedling. The field population was suitable. And the grain yield of the three treatments was higher than CK because of more grain per spike and higher weight of per 1000 kernels. But the field seedling emergence rate of zero tillage was only 60.2%. Yield of winter-wheat was significantly lower than CK because of deficient population.Through the analysis of affecting force, we can conclude that independent effect of soil tillage was the most important resource of variation. The basic seedling, Max winter tillering, Max spring tillering, spike per hm2, kernel per spike, weight per 1000 kernels and grain yield were significantly affected by independent effect of soil tillage. The affecting force of straw management was lower than that of soil tillage. The Max winter tillering and kernel per spike were also significantly affected by the interaction of soil tillage and straw returning. The affecting force of that was 6.17% and 28.87%.3 The response of maize to the increase of soil bulk density was not sensitive. The yield of maize was enhanced significantly by the compound of wheat straw mulching and aftereffect of zero-tillage, rotary-tillage, harrow-tillage, and subsoil-tillage. The yield of maize in the four conservation tillage was higher than conventional tillage by 5.3%, 6.5%, 6.3% and 3.4%.Allelopathic compounds in the rain extracts of wheat straw led to significant effect on maize seedling emergence rate. The seedling emergence rate of treatment with wheat straw covering is significantly lower than that of treatment without wheat straw. The degressive range reached 7.37% in 2005 and 6.05% in 2006. By the comparison of different tillage, the highest seedling emergence rate was in conventional tillage and another extremity was in zero tillage. The discrepancy of them was 6.2% and 9.2% in the two years. So a higher sowing norm should be adopted in order to ensure an adequate population of maize in the field of wheat straw covering. The result showed that the dry matter accumulation rate was enhanced and that the active accumulation stage was prolong in the treatments of 4 conservation tillage with wheat straw covering. The similar was the rule of kernel filling. It's advantageous to the plumpness of maize kernel and augment of kernel weight.The analysis of affecting force on yield and yield components of maize indicated that the independent effect of soil tillage was superior to that of straw and their interaction. The yield of maize in 2005 was significantly affected by the affecting force of soil tillage. The value of that reached 48.8%.4 Through compositive value analyse, the conservation tillage increase ecosystem services value significantly compared with the conventional tillage. The compositive value of PH and PS was higher than that of CK by 7270.9$/hm2,5587.9$/hm2. Among all the treatments, PH and PS were better to be spread, which had higher economic and ecological value.The evaluation of agri-ecosystem service in 10 treatments showed that the primary products value and value of carbon fixation and oxygen release were very important in the compositive evaluation. It's helpful to enhance the primary products value of conservation tillage that the mechanical cost was saved because of less working procedure. Organism yield in straw returning treatment of rotary tillage, harrow tillage and subsoil tillage was higher than CK. So was the value of air modulation. Conservation tillage with straw returning could increase the pondage of soil. So the value of reserving water was higher than CK. As far as the independent effect of straw returning was concerned, it could increase 108.6$/ hm~2 in average. The value of zero tillage, rotary tillage, harrow tillage and subsoil tillage was 204.7$/hm~2,169.1$/hm~2,117.2$/hm2,87.2$/hm2 higher than that of CK.
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