| This research was conducted in the field in Shandong Agricultural University in 2005-2008, which was to explore the changes of nutrition in soil and the response of crops to conservation tillage. Two crop species, wheat and maize, were planted every year in this farming system. Some parameters including physical and chemical characters, microbial properties, and enzyme activities, greenhouse gas of the soil and development of crop growth were examined at different season of each year, and the effects of conservation tillage on these parameters were analyzed. These results can give some suggestions for the application of different tillage patterns in the sysytem of high efficiency and low expending agriculture.The major results were as follows.1.The effects of conservation tillage on soil physical charactersStraw returning could increase the content of water-steadied coacervate in the soil layer between 0-30cm upright levels. Conservation tillage could increase the content of water-steadied coacervate in the soil layer 0-10 cm upright level. The soil decentralization coefficient of the conservation tillage was less than that of conventional tillage. Conservation tillage significantly increased soil capillary hole linear measure, straw returning was propitious to increase soil hole linear measure, but tillage modal decided the non-capillary hole linear measure.When straw was returned to the soil, the using efficiency in PS was the highest. And when same tillage technique was used, the using efficiency was higher in straw returning treatment than no straw returning.2. The effects of conservation tillage on soil chemical charactersStraw returning was helpful to improve organic matter content, and the increase of organic matter conten was greater in conservation tillage than conventional tillage in 0-10cm soil layer. In few and no tillage modals, organic matter content in 0-10 cm soil layer was more in10-20 cm, but it was reverse in conventional tillage treatment.Under no straw returning, subsoiling tillage and harrow tillage modals were benefited to the improvement of total N in surface layer of 0-10cm. But under straw returning treatment, the total N content in rotary tillage and harrow tillage was significantly higher than no straw returning.The total N accumulation of deep scarification treatement was higher than conventional tillage, but those of no tillage, rotary tillage and harrow tillage treatmwnt were lower than conventional tillage.Straw returning avail to increase AN content , available P , available K in the soil. The AN content in few tillage was higher than conventional tillage. The increase of available P conten was the gretest in conventional tillage and straw returning treatement in 0-20cm cultivating soil layer. No tillage with no straw returning could increase available P content in sampling date. In 20-40cm tillage layer, in all cultivating treatment, the highest available K content was found in the harvest season in the process of crop development, and on regularity was found in other seasons.3. Effects of conservation tillage on soil microorganismsThe average numbers of bacteria(except conventional tillage with no straw returning), set bacteria(except conventional tillage with no straw returning) , epiphyte in 0-10 tillage layer were more than 10-20cm . In 10-20cm tillage layer, the numbers of bacteria in conservation tillage were less than conventional tillage. The average numbers of set bacteria in 0-20cm tillage in layer in conventional tillage with straw returning were highest, no tillage were the lowest . The soil microbial biomass C,active microbial biomass,microbial activity and mirobial quotient in 0-10cm in conservation tillage were bigger than in 10-20cm. conservation tillage and straw returning was helpful to improve soil microbial biomass C. conservation tillage conservation was helpful to improve active microbial biomass and microbial activity in 0-10cm.The microbial activity in 10-20 soil layer in no tillage was the lowest. the catalase activity of conservation tillage treatment was higher than conventional tillage,no tillage was the lowest,straw returning than no straw returning. Mirobial quotient in conservation tillage was higher conventional tillage. 4. The effects of conservation tillage on soil enzyme activitiesIn conservation tillage, the urease activity in 0-10cm soil layer was higher than in 10-20cm, but that was reverse in conventional tillage. Straw covertion was benefit to sucrase activity in 10-20cm soil layer. Sucrase activity in conventional tillage with straw returning was highest, and no tillage was lowest . In 0-10cm soil layer, the catalase activity of conservation tillage treatment (except PS) was higher than conventional tillage. In 10-20cm soil layer, soil enzyme activities in PZ was depressed, and soil enzyme activities was improved in PS and C treatment. Straw returning was benefit to improve soil enzyme activities.5. Effects of conservation tillage on greenhouse emission in the fieldThe fields of conservation tillage were the sink of CH4 absorption. Comparing with the field of conventional tillage, CH4 absorption fluxes of conservation tillage field were reduced. A positive correlation was found between CH4 absorption fluxes and temperature in conservation tillage field, and a negative correlation was found that with soil water content. The temperature and soil water content were not related to CH4 absorption fluxes in conventional tillage. A significant negative correlation was existed between CH4 absorption fluxes and NH4+ content in different treatments. The difference of N2O fluxes between conservation tillage field and conventional tillage was significant except no tillage with Straw returning treatment. Comparing with conventional tillage, N2O fluxes of conservation tillage (except NS) were increased significantly. The temperature was the primary factor that influencing N2O emission, N2O emission was enhanced with the increase of temperature.Water content and mineralized N of soil were not related to N2O emission. The CO2 emission fluxes was the highest in PA, and that was the smallest in PZ treatment.Straw returning was availe to emission of CO2 from soil. A positive correlation was found between CO2 emission fluxes and temperature in conservation tillage, and a negative correlation in soil water content. The soil water content was not related to CO2 emission in conventional tillage.The fields of conservation tillage were the sink of CH4 absorption in maize season. The lowest CH4 absorption fluxes were found in seedling stage and the highest was in grouting stage of maize. The order of CH4 absorption fluxes among different tillage models were: conventional tillage with no straw returning (AC) > conventional tillage with straw returning (PC) > subsoiling tillage with straw returning (PS)>harrow tillage with straw returning(PH)>rotary tillage with straw returning (PR)> zero tillage with no straw returning (PZ) The apex value of the N2O emission fluxes was found in seedling period and big-gob period, and the lowest apex value was in gain period. The N2O emission fluxes in conservation tillage were bigger than in conventional tillage. CO2 emission fluxes were the lowest in seedling stage, and the highest level of it was in big-gob stage. CO2 emission fluxes were bigger in conventional tillage than in conservation tillage.The general greenhouse effect was bigger in conventional tillage than in conservation tillage, zero tillage was the lowest in all treatment, and the biggest level of it was found in conventional tillage with straw returning treatment. Greenhouse effect was bigger in corn growth season than in wheat growth season. N2O and CO2 increased greenhouse effect, but CH4 decreased greenhouse effect. CO2 emission is the major factor in greenhouse effect.6. Effects of conservation tillage on the plant development and yieldThe basic seedling of wheat was lower significantly in zero tillage than in conventional tillage.The max winter tillering was slightly different with basic seedling of wheat. Harrow tillage with straw returning and harrow tillage with no straw returning were higher than conventional tillage with no straw returning, zero tillage with no straw returning, subsoil tillage with no straw returning, zero tillage with straw returning and subsoil tillage with straw returning were lower significantly than conventional tillage with no straw returning, but that of harrow tillage with no straw returning was no different with CK. In max spring tillering, no significant difference was found among AS, PH and AC, but that of zero tillage with no straw returning and zero tillage with straw returning were lower significantly than conventional tillage with no straw returning.In wheat growth season, in straw returning treatment, the numberof spike per hm2 was highest in conventional tillage; the weight per 1000 kernels was higher significantly in subsoil tillage than in conventional tillage, and that of zero tillage treatment was lower significantly than in conventional tillage; the grain yield was higher in subsoil tillage than in conventional tillage, and that of zero tillage and rotary tillage treatment was lower than conventional tillage treatment. In no straw returning treatment, the numbers of spike per hm2 was lower significantly in subsoil tillage, zero tillage and rotary tillage than in conventional tillage, and kernel numbers per spike was lower significantly in zero tillage and rotary tillage than in conventional tillage. Weight of per 1000 kernels was higher significnatly in subsoil tillage than in conventional tillage. Grain yield was higher in subsoil tillage than in conventional tillage, and that was lower in zero tillage and rotary tillage than in conventional tillage. In corn growth season, in straw returning treatment, the effects of conservation tillage on corn spike and spike row were significant. Weight of per 1000 kernels was higher in subsoil tillage than in conventional tillage, and that of zero tillage and rotary tillage was lower significantly than conventional tillage. Grain yield were higher in subsoil tillage and harrow tillage treatment than in conventional tillage, and that of zero tillage and rotary tillage were lower than conventional tillage. In same tillage treatment, grain yield were higher in straw returning than in no straw returning.
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