The Effect Of Hedgerows On Slope Farmland Ecology In The Purple Hilly Agricultural Area

Though choosing Medicago sativa, Vetiveria zizanioldes, Amorpha fruticosa, Coronilla varia and Eulaliopsis binata as the central materials, soil erosion quantity of different forage dedgerow pattens, the space redistribution law of soil nutrient in the system, the interaction and energy utilization relationship of various components in dedgerow cropping system, diversity change rules of farmland arthropod and microorganism were deeply studied by the method of long-term(eight-year) located, it provided theoretical basis for optimizing and innovating dedgerow agricultural pattern. The results were as follows:1.The amounts of runoff and sediment were decreased significantly after planting hedgerows, the effect of controlling soil erosion was good and quick. The energy out-input ratio of whole system was improved by hedgerow, it was a effective measure of improving agricultural energy efficiency in Sichuan hilly area. Leguminosae forage hedgerows provided favorable evacuee shelter for ground-dwelling spiders, whose activity density was significantly improved than in the bare soil strips during the winter wheat season, and the diversity was also enriched. The amounts of soil bacteria, actinomycetes, fungi of the VH and AH treatments, microbial biomass carbon and ammonification activity were increased by hedgerows. So the farmland ecology of purple soil was significantly improved by hedgerows, forage hedgerow system was one of surstainable farming methods in the purple soil area of Sichuan province.2. Using the standard soil erosion monitoring plot and the SW 40 diary water level recorder to monitor the effect of different hedgerows against the control treatment on soil erosion and fertility. Results showed that, the amounts of runoff and sediment were decreased significantly after planting hedgerows,165.4-242.8 t/hm2 sediments were totally reduced in 8 years, the amounts of runoff and sediment were reduced by 63.0%-70.8% and 79.1%-85.7% in the following year of planting hedgerows, the effect of controlling soil erosion was good and quick. The soil grade significantly eliminated after planting hedgerows, the slope gradient of two plots respectively decreased from 20°,13°to 16°28' and 17°11',10°28'and 11°5'. There was obvious sediment deposition in the upper part of hedgerows, the average clay contents of Vetiveria zizaniode, Medicago sativa, Eulaliopsis binata's soil zone above the hedgerows were 29.6%,28.9%,33.1%,6.6% and 6.5%,5.9% and 9.3%,7.0% and 15.0% respectively more than middle zone and zone below the hedgerows(Relative difference), clay particles tended to accumulate above the hedgerows and to be eroded downward below the hedgerows along contour lines across the field. Distribution of soil organic matter and all plant nutrients except K showed the same pattern as the clay particles. Potassium (K), however, was evenly distributed in the field without any noticeable influence from the hedgerows. Since the fixed experiment started, soil P has kept accumulating, the average total P contents of Vetiveria zizaniodes, Amsopha fruticosa, Medicago sativa and Eulaliopsis binata hedgerows were respectively up to 0.105%, 0.098%,0.096%,0.090%, increased by 54.1%,44.1%,35.2%,26.8% more than that of total P content of initial soil. While soil organic matter and K were in depletion, the organic matter content of all treatments decreased compared to the beginning of experiment, the organic matter content of control treatment and Vetiveria zizaniodes, Amsopha fruticosa hedgerows were decreased by 34.3%,25.8%,21.8% in field no.1, the organic matter content of control treatment and Medicago sativa, Eulaliopsis binata hedgerows were decreased by 25%,21.9%,30.2% in field no.2, K content had the similar statement.3. The energy flow characteristics of "crop-hedgerow" system, such as the structure and efficiency on slopping land(8-20°) had been studied for 2 years. There were 3 main conclusions.①The quantity and structure change of output and input energy of "crop-hedgerow" system was mainly affected by the type of hedgerow subsystem, in comparison with the traditional crop production system on large area sloping land, for instance, wheat/peanut(or corn)/sweet potato system:there was difference between hedgerows (including fruit tree, herb etc.) and crop in shape and space distribution of crown and root so that the natural resources of light, heat, water and soil were continuously utilized in time and space, which enhanced light energy utilization efficiency, input labour energy utilization efficiency and total output energy per unit area. The light energy utilization of Vetiveria zizaniodes, Amsopha fruticosa and intercropping pear and yellow flower pattens were increased by 24.62%,14.78% and 15.60% respectively, the increased range of "crop-herb" hedgerow system's input labor energy utilization efficiency was up to 67.88%-102.32%, the steeper the sloping land, the higher the relative amplitude, the increase amplitude of field no.1 was 9.8%-25.62%, and which of no.2 and no.3 was 1.2%-15.61%. Compared to control treatment, all the input inorganic energy was reduced significantly through planting hedgerows, the reduction amplitude was up to 30.0%-41.0%, the quantity of chemical fertilizer and pesticide can be reduced, resulting environment protection.②The total input energy (including organic energy) of "crop-fruit" hedgerow system was increased, which of "crop-jujube", "crop-pear/yellow flower", "crop-loquat/yellow flower"system were increased by 21.6% and 69.8%,43.7% and 46.1%, 43.5% and 146.2% respectively. It was useful for improving input energy structure and ecosystem, and enhancing intensive agriculture development.③Choosing Vetiveria zizaniodes, Amsopha fruticosa, Coronilla varia and Medicago sativa as the hedgerow of "crop-herb" hedgerow system, the input artifical supplementary energy was greatly decreased, the fewer demand of input energy and the low level of organic and inorganic energy resulted in increasing the input labour energy utilization efficiency and biomass, energy out-input ratio of inter-planted crops, the increase amplitude of four hedgerows' energy out-input ratio were 40.93%,8.21%,39.38%,42.91% respectively, hence the energy out-input ratio of whole system was improved to 64.15%,45.03%,41.50%,40.79%. It conserves water and soil, play an important role in agricultural reform in vast mountainous and hilly area in Sichuan.4. We investigated the effects of four hedgerow plant species, which served as undisturbed and permanent semi-natural habitats, on ground-dwelling spider activity density (a parameter of population density and relative activity) by using pitfall trapping methord. Samples were collected over two winter wheat and two summer maize growing seasons during 2005-2007 in trial field 1 (slope gradient of 20%) and field 2 (slope gradient of 13%). The hedgerow species evaluated were Amorpha fruticosa (field 1), Vetiveria zizanioides (field 1), Eulaliopsis binata (field 2) and Medicago sativa (field 2). The results showed that:activity density of ground-dwelling spiders was significantly higher in the hedgerow strips than in the bare soil strips during the winter wheat season. Activity density of ground-dwelling spiders was also higher in the hedgerow strips than in the bare soil strips during the summer maize season, however, only the Eulaliopsis and Medicago strips had significantly higher activity densities of ground-dwelling spiders than the bare soil strips. Activity density of ground-dwelling spiders in the crop fields did not differ significantly between hedgerow and control plots during the winter wheat or summer maize seasons.5. Though determining soil microbial quantity, microbial biomass carbon and nitrogen, soil ammonifying capacity, soil nitrifying capacity and soil Nitrosation capacity of different treatments, studying genetic diversity separated from different plant hedgerow treatments of soil ammonifying bacteria and rhizobia by using BOXAIR-PCR and 16S rDNA PCR-RFLP methods, then squencing analysis representative strain, the effect of different plant hedgerow on population characteristics of ammonifying bacteria and rhizobia was revealed.The results showed that, compared with CK, the amounts of soil bacteria, actinomycetes and fungi of the VH and AH treatments were increased by 63.43% and 36.63%,47.87% and 71.89%,74.60% and 43.65%; MBC was increased by 90.02% and 24.97%; MBN was increased by 83.32% and 45.04%; ammonification activity was increased by 73.28% and 75.65%; however, nitrosification and nitrification activity was decreased by 26.97% and 52.96%,6.46% and 22.19%, respectively. The 16S rDNA PCR-RFLP analysis results of bacteria and rhizobia showed that, genetic types separated from Vetiveria zizaniodes and Amsopha fruticosa treatments of soil ammonifying bacteria and rhizobia were more than CK. The squencing results of representative strain showed abundant genetic diversity.