Comparison Of Crop Productivity And Nutrient Loss In Multiple Cropping Systems And Technological Studies In Conservation Tillage Systems In Danjiangkou Reservoir Area

As the water source of the middle line of South-to-North Water Transfer Project, the ecological safety and water quality in Danjiangkou Reservoir catchment are associated closely with the success of the project implementation. In this study, aimed at the worsening problems of agricultural non-point source pollution and declining water quality in the area, field experiments were conducted to test the differences in runoff amount and its pollutant contents on the farmland of different cropping patterns. While, the nutrient absorption of crops and the changes in soil nutrient contents were also determined. At the same time, some related technologies suitable for conservation tillage modes were studied in maize plantation of wheat-maize rotation cropping system on slope farmland and rice plantation of oilseed rape-rice rotation cropping system. The purpose of the above studies is to provide technological support for controlling agricultural non-point source pollution from source emergence in this area. The main results are as follows:1. The productivity and economic income were higher in oilseed rape plantation than that in wheat plantation in winter cropping season, while, maize plantation got higher economic income than sweet potato plantation in summer cropping season on slope farmland. Increasing fertilizer application could improve significantly crop yield and economic benefit, except for sweet potato plantation, on the basis of current common fertilizing level. Among different cropping systems, oilseed rape-maize is the optimal rotation pattern in economic in the region.2. Runoff amount and soil erosion on the farmland was affected significantly by crop rotation patterns. Under same fertilizing rate, both total amount of runoff and soil erosion were the highest in wheat- sweet potato pattern, while, there was not significant difference between oilseed rape-maize and wheat-maize patterns.3. Under farmer's common fertilizing rate, the amount of total nitrogen (TN), total phosphorus (TP) and dissolved potassium (DTK) losses was the lowest in wheat-maize pattern; TN and TP losses were the highest in wheat-sweet potato pattern, and DTK losses was the highest in oilseed rape-maize pattern. Under high-yielding fertilizing rate, TN, TP and DTK losses were the highest in wheat-sweet potato pattern; TP and DTK losses were the lowest in wheat-maize pattern, and TN loss was the lowest in oilseed rape-maize pattern. In addition, the main form of TN loss was NO3-N, and particle phosphorus (PP) was the main form of TP loss. The preferable environmental friendly cropping rotation system is wheat-maize rotation under the farmer's common fertilizing rate on the slope farmland in this area. However, increasing fertilization on the current common level, the risk of nitrogen loss may rise in wheat-maize pattern, TP loss may rise in oilseed rape-maize pattern, and TP and DTK losses may rise in wheat-sweet potato pattern.4. Under same fertilizing rates, the highest absorption of N, P and K was found in oilseed rape-maize rotation pattern, but less differences were found between wheat-maize and wheat-sweet potato patterns. With increasing fertilizing rate, nutrient absorption showed a significant increase in every pattern.5. Compared between intercropping systems, the economic benefit was higher in wheat//vicia faba and maize//soybean intercropping pattern in winter and summer cropping season, respectively. At the same time, the nutrient absorption of crops were also higher in the two patterns.6. In different multiple intercropping systems under farmer's common fertilizing rate, the runoff amount and soil erosion were the lowest in wheat//pea-maize//soybean system; Phosphorus and potassium losses were the lowest in wheat//vicia faba-maize//soybean system, while, the nitrogen, phosphorus and potassium losses were the highest in wheat-maize system but without significant differences; nitrogen, phosphorus and potassium losses were lowest in wheat//vicia faba-maize//soybean system. Therefore, the preferable environmental friendly plantation pattern is wheat//vicia faba-maize//soybean cropping system for controlling phosphorus outflux from farmland for avoiding eutrophic risk in the reservoir.7. In wheat-maize rotation system on slope farmland, maize yield could be improved to a certain degree by both straw-mulching and applying potassium along with nitrogen application for times, but without significant effect. While, straw-mulching and balanced fertilization were conducive to maintaining soil nutrient and soil micro-environment.8. In the non-tillage relay intercropping system of rice with oilseed rape, the highest rice yield reached amount of 8190.1 kg·hm-2 under the optimum direct sowing density of 52.5 kg·hm-2. Results showed also that, rice yield was mainly determined by the effective panicle number per hectare in this cropping system. Although the higher yield could harvested, the soil available nutrient did not decrease under the suitable sowing density.