| Soil erosion, Soil hydrothermal regimes, Soil microbiology indexes can be studied for assessing the sustainability of agricultural ecosystems. The experiment was conducted at a typical slope field in Qingshuihe County of Inner Mongolia for a period of 4 years (2005–2008). The objective was to determine the influence of five tillage practices, such as no tillage with low stubble (NL), no tillage with high stubble (NH), no tillage low stubble with residues (NLS), no tillage high stubble with residues (NHS) and conventional tillage (CT) practices, on soil characteristics and crop yield. The results showed that :(1) No tillage with residues and no tillage practices could decrease soil erosion, NS decreased runoff by 21.92%, soil loss by88.34%compared to CT, respectively. Topographic gradient has important influence on soil and water loss. In general, the changing trend is that the soil and water loss aggregates with the increase of gradient, under the same topographic condition, different crops'runoff and soil loss show obvious disparity. We discussed the correlations between rainfall and oil &water loss in three different tillage styles, the fitting models are built and the R square all are over 0.9. The regression equation is y=axb. It benefits No-tillage.(2) There was a significant effect of no tillage with residue on soil temperature and soil temperature followed diurnal variation depending on the season although the magnitude decreased with soil depth. Maximum value of the surface soil layer (0—10 cm) was 17.6—34.0℃; the soil temperature was lowest at 0600 hr, the maximum value at 1500 hr; During whole growth period, soil moisture content of NHS increased by 7.37% , NLS by 5.93% compared to CT: At seeding stage, soil moisture content increased with soil depth up to a depth of 100 cm, at the tillering stage, it was low in 0—20 cm, at flowering stage it was low in 0—40 cm depth, followed by a gradual increase up to 100 cm depth. The moisture content also was affected by season and with the rainfall. Thermal capacity increased as soil organic matter increased and the NHS had a buffering effect on the soil temperature. In rain-fed areas of the Yellow River basin this study will help the farmland management.(3) Conservation tillage treatments had higher soil microbial biomass (carbon, nitrogen and phosphate) than conventional tillage in 0–10 cm soil depth, which was in order of NHS>NLS>NH>NL>CT in 2007 and 2008. Soil organic matter and nutrient content in 0–10 cm soil depth under different tillage were changed in the following order of NHS>NLS>NH.>NL>CT in 2007 and 2008. The maize yield gradually decreased during the first three years but increased for the 4th year. Soil properties have positive correlations with maize yield. Our path analysis indicated that the soil total nitrogen, total phosphorus, available phosphorus and microbial biomass carbon have direct effect on maize yield, especially soil microbial biomass carbon. The results also indicated that no tillage was advantageous to improve soil fertility in rain-fed farmlands of Inner Mongolia.(4) No tillage could raise soil microbial biomass (carbon, nitrogen and phosphate), followed by treatments NHS>NLS>NH>NL>CT. Contents of soil microbial biomass in soil depth layer followed the order: 10cm>20cm>30cm>40cm, but soil microbial biomass carbon in soil 20cm depth layer of CT is higher than other depths. Soil microbial biomass carbon has the same tendency as soil microbial biomass nitrogen and phosphate; it showed contents of soil microbial biomass in July is higher than June and August. Change of Leaf area index (LAI) is unimodal curve, plant height and dry matter accumulation as"S"curve. All of crop indexes followed the order in the treatments: NHS>NLS>NH>NL>CT. Soil microbial biomass have positive correlations with crop indexes, especially the correlations of Soil microbial biomass phosphate with crop indexes. Soil microbial biomass carbon and nitrogen were strongly affected by crop growth in August.(5) We measured alkaline phosphatase, invertase, hydrogen peroxidase and urease, enzyme activities in NHS are enhanced by 57%, 82%, 92% and 25% respectively, over CT. The, phosphatase reached peak in June, while others'peak in July.
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