| Danjiangkou reservoir is the water source of the middle line of South-to-North Water Transfer Project, therefore, its water quality relates to the safety of drinking water in Beijing, Tianjing and Hebei in the near future, and is also a determinant for the success of the project. Being aimed at the current situation on the rising eutrophication trend in the reservoir and increasing load of agricultural non-point source pollution in the area, in this paper, we compared the differences in crop produtivity and runoff nutrient loss from slope farmland in different rotation patterns of winter and summer crops under different fertilizer application rates. The purpose is to provide with a trial basis for controlling agricultural non-point source pollution. Meanwhile, a'3414'trial design was adopted to study the appropriate fertilizer application rate and fertilizer use efficiency in relay cropping rice with wheat, in order to promoting the new conservation tillage technology. The main results are as following:1. The productivity and economic income were significantly higher in rape (Brassica napus) plantation than that in wheat (Triticum aestivum) plantation and increasing fertilizer application could improve significantly crop yield and economic benefit on the present level in winter crop plantaion on slope farmland. In summer cropping systems, maize (Zea mays) plantation got the highest economic income. Increasing fertilization could improve significantly the maize yield and its economic benefits in'rape-maize'and'wheat-maize'rotation patterns on the present fertilization level, but could not increase sweet potato (Ipomoea batatas) yield in 'wheat-sweet patato'pattern. The sesame (Sesamum indicum) productivity in'rape-sesame'rotation pattern was slightly higher than that in'wheat-sesame'pattern but without a significant difference. Considering crop productivity and econimic efficiency, the optimal rotation pattern was 'rape-maize'on slope farmland in the region.2. Runoff amount and soil erosion on the farmland was not only affected significantly by precipitation, but also by crop rotation patterns. Under farmer's fertilizing rate, total amount of runoff and soil erosion were highest in'wheat-sesame'pattern, where, they were lowest in'wheat-maize'pattern. Under high-yielding fertilizing rate, the highest runoff and soil erosion was found in'wheat-sweet potato'pattern, but the lowest runoff in'rape-maize'pattern and the lowest soil erosion in'wheat-maize'pattern among the three local traditional rotation patterns. Runoff production and soil erosion were usually higher in the early stage of crop growth, but lower in the late stage. In the whole year of crop plantation, the runoff and soil erosion accounted for more than 70%of total amount during summer cropping season.3. Nutrient loss from runoff on the slope farmland was related closely to the precipitation. It was shown that, nutrient loss increased along with the increasing rainfall, and the loss proportion was larger in the early stage of two season crops. Under farmer's fertilizing rate, the amount of TN loss was the lowest in'wheat-maize'pattern, but the highest in'wheat-sesame'pattern because mainly of increment of NO3N loss ratio; The lowest TP loss was found in'wheat-maize'pattern, but the highest in'rape-sesame' pattern perhaps because mainly of increased loss in particulate adsorptive phosphorus; The lowest DTK loss was found in'wheat-maize'pattern, but the highest in'rape-sesame' pattern. With increasing fertilizing rate, TN loss showed an increasing trend in 'wheat-sweet potato'pattern, TP loss showed an increasing trend in'rape-maize'pattern, and DTK loss showed an increasing trend in 'wheat-sweet potato'pattern.4. Crop nutrient absorption changed significantly in different rotation systems, which might be one of factors that affected nutrient loss on farmland. Under farmer's fertilization rate, the highest nutrient absorption of N, P and K was found in'rape-maize' pattern, and then followed by 'wheat-maize'pattern. Under high-yielding fertilization rate, crop nutrient absorption showed an increasing trends.5. In different crop rotation systems, the contents of soil organic matter and alkali-hydrolyzable nitrogen showed a decreasing trend, but olsen-P and available-K showed an increasing trend after plantation and the trends became more obvious under high-yielding fertilization rate.6. From the consideration on reducing nitrogen and phosphorus loss in Danjiangkou reservoir area, the first preferable crop rotation on slope farmland should be 'wheat-maize'pattern, the second was'rape-maize'pattern. However, increasing fertilization on the current level, the risk of nitrogen loss might rise in 'wheat-maize' pattern, and phosphorus loss might rise in 'rape-maize'pattern.7. Rice yield was mainly detemined by the effective panicle number per hectare and total grains per panicle, and appropriate application of N, P and K fertilizer increased yield significantly and therefore, increasd farmer's economic income in relay cropping rice with wheat. The highest grain yield reached amount of 6889 kg·hm-2 when fertilization rates were 168.0 kgN·hm-2,75.0 kg P2O5·hm-2 and 90.0 kgK2O·hm-2. 8. In relay cropping rice with wheat, among the effects of N, P and K fertilization, the increments of yield production decreased in order of N>K>P. The highest increment rate was 92.8%with an the apparent nutrient efficiency of 52.9%under N application; 8.6%with 13.0%under P application, and 11.3%with 69.8%under K application, respectively. Modelling on fertilization effect showed that, the appropriate application rates of N, P2O5 and K2O were 188.0,30.0 and 85.0 kg·hm-2, respectively.
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