| Soil and water loss is a severe problem in the gully region of the south Loess Plateau where precipitation is rather deficient. Therefore, better water and nutrition management in the region is a major approach to improve the productivity of farmland. In this study, soil water, soil nutrition and winter wheat growth on farmland were investigated under different gradients and lengths, and fertilizations on the tableland in Changwu Agro-ecological Experimental Station on Loess Plateau, Chinese Academy of Science. The main results were reported as follows:1. Significant effects of different slope gradients and slope lengths on the water characteristics on the tableland. For the slope length of 50m, volume of runoff under different surface conditions was different. Landuse, in terms of volume of runoff, ranked in the descent order of winter leisure-seeding, maize leisure-seeding and bare land. For the slope length of 20m and the slope gradients of 0.5°, 1°and 3°, volume of runoff correlated positively with slope gradients. Slope gradients, in terms of soil water content, ranked in the descent order of 0.5°, 3°and 1°, before seeding winter wheat.Because precipitation increased after winter wheat harvest, soil water content was enhanced with the increased depth of soil, and was in a positive balance. Evapotranspiration(ET) in the 1°treatment was maximal, being 14% higher than that in the 0.5°treatment and 30% higher than that in the 3°treatment. For 0.5°slope gradient and 20m and 50m slope lengths, soil water content increased as slope length increased. During the growth period after leisure-harvest of winter wheat, ET in field with the treatment of 20m slope length exceeded precipitation, whereas ET in field with the treatment of 50m slope length was slightly below precipitation.2. The effects of different slope gradients of the tableland on nitrogen (N), phosphorus (P) and organic matter. For the treatments of 20 m slope length and 0.5°, 1°and 3°of slope gradients. Slope gradients, in terms of contents of total N, NO3-1-N, total P, effective P and organic matter after harvest of winter wheat ranked in the descent order of 0.5°, 3°and 1°. NH4+-N in soil decreased as gradient increased.3. The effects of slope gradient of the tableland on winter wheat growth. Leaf weight and straw weight of winter wheat in the treatments of 20m slope length and 1°and 3o slope gradients were significantly different. However, differences in weight in the treatments of 1°and 3°slope gradients were not significant compared with that in the 0.5°treatment. Differences of ground biomass, seed production, index of harvest, thousand-grain weight, ET and water use efficiency (WUE) in the treatments of 0.5°, 1°and 3°of slope gradients were not significant, of which WUE was 8.9kg·m-3. 4. Significant effects of different fertilizer applications on water characteristics. Soil water content decreased with winter wheat growing for different treatments of fertilizer application. After booting stage, soil water content in CK treatment increased more rapidly than that in other treatments, and soil water content in N180P60, N180P120, N180P120K90 treatments increased slowly. Compared with CK treatment, application of N could significantly increase ET, and difference in field ET resulted from application of P at the level of N90 treatments was not significant. However, ET at the level of N180 treatment was significantly different. ET in N180P120 treatment was 61% higher than N180P60, and 50% higher than N180P120K90.5. Effects of different fertilizer applications on soil nutrition. N, P and organic matter in soil were enhanced as fertilizer increased. NO3-1-N, effective P and organic matter in N180P60, N180P120 and N180P120K90 treatments were significantly higher than those in N90P60 and N906120 treatments. NO3-1-N in N180P60, N180P120, N180P120K90 treatments suffered from serious eluviations.6. Compared with CK treatment, application of N influenced leaf area index during booting and anthesis, but did not significantly influenced photosynthetic rate (Pn). Application of N affected transpiration rate (Tr) mainly before booting stage, and could significantly enlarge the leaves'weight, yield, thousand-grain weight and biomass. Application of P significantly influenced Pn and WUE at leaves level during anthesis, Tr and WUE at leaves level during wintering, and the effect occurred after the booting stage. Effect of N interactions with P on photosynthetic character was not significant, but the effect was significant on ET. Fertilizer application can improve photosynthetic character, increase ET and enhance yield and WUE. In the gully region of the Loess Plateau, the optimal amounts of N and P applications for winter wheat growth were found to be 180kg·hm-2 and 60 kg·hm-2, respectively...
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