| The Water-Fertility and their improving technology (WFI) was studied in Pingshan County Hebei province in the dissertation. The analysis of climate and soil conditions was first carried out to provide the basis for the proceeding of WFI. Then, combined with the climate analysis in trial areas, Water-Fertility of different tree species was studied. In order to efficiently utilize the local precipitation resource, the effect of water-retaining agents and late-model fertilizers on water utilization was discussed and water-fertilizer coupling was primary researched. The main results showed as follow:1. The climate data of trial areas in 1998-2002 was analyzed and was compared with that of trial and perimeter areas in 30yeas (1961-1991). The result showed that atmosphere temperature increased 1°C in last 30 years, the precipitation declined and the evaporation and other climate indices were nearly the same. The comparison of precipitation and the evaporation climate data showed that the arid of study area displays the drop tendency.2. The soil analysis in trial areas with different soil, climate and vegetation conditions implied that the soil in trial areas mainly belongs to drab soil, soil texture belong to light loam and loam soil, soil parent material was mainly granite and gneiss. The chemical character analysis showed that the soil in trial areas is poor, the pH is neutral, macro- and micro-elements contents expressed complex rules in different soil, climate and vegetation conditions. The soil conditions between the reused farmland and rude land were different significantly.3. The relative analysis for the evaporation and ground temperature et al climate indices in 1998～2002 showed that the main factors affecting evaporation were atmosphere pressure and ground temperature. The evaporation in trial areas was corrected by the detection of ground temperature. The water equilibrium formula with different soil, climate and vegetation conditions was utilized to study the water carrying capacity of different tree species by the method of which the water carrying capacity of the tree subtracted that of control.4. The results of water-retaining agents experiments on Acacia showed that reasonable applying water 5. retaining agent (the ratio of deal to soil about 0.1%) can increase the soil water content significantly, facilitate the growth of Acacia and promote the soil construction. The observation for 3 years proved that the root of Acacia absorb the retaining water in water retaining agents.6. The result of late-model fertilizer experiments on different tree species showed that pure fertilizer applying may promote the growth of Walnut. On the basis of pure fertilizer, applying microbe and bacteria manure not only increased the growth of Walnut, Wild pepper, Oriental arborvitae, Tetraploid Black locust, Negundo Chastetree but also alleviated the vice effect of the pure fertilizer. The analysis on the photosynthesis and scope crown showed that reasonable fertilizer applying can increase the photosynthesis and LAI. In addition, microbe manure benefit to the balanced distribution of scope crown.7. The water and fertilizer coupling study on 2-year seedling and 6-year fruited Walnut proved that reasonable water fertilizer controlling facilitated water and fertilizer utilization on the basis of the promote of growth. These results benefit for the proceeding of water and fertilizer alternating design. The season variety of soil humidity, total nitrogen and available nitrogen expressed that reasonable nitrogen applying can efficiently make use of limited precipitation in trial areas. The experiment results of 6-year fruited Walnut were complicated because of artificial interference seriously, but still expressed the trend that nitrogen adjusted the water.
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