Taihu Source Sloping Under Phyllostachys Praecox Stands Soil Nitrogen, Phosphorus Loss Characteristics And Intercept Control Study

The Lei bamboo (Phyllostachys praecox f. Preveynalis) production is the main economic pillar industry in the region of Tiaoxi River. In order to improve the economic profit of Lei bamboo production, a technique of mulching method with a large fertilizer application rate was employed. At the same time, the measures of reclamation and weeding can lead to soil disturbance and erosion that will eventually increase N and P entering Taihu Lake and a risk of eutrophication. Therefore, it is important to control N and P in situ to minimize their loss to rivers and will be benefit for the improvement of water quality of Taihu Lake. In this thesis, a slope Lei bamboo site was selected and 4 runoff interception treatments were set up in the area of Taihu Lake origination. There were 4 buffer strips setup including original bamboo stand, bamboo + bamboo charcoal, ecological grass, ecological grass+ bamboo charcoal to monitor N and P runoff losses and investigate their control effects on N and P runoff from Lei bamboo stands. In addition, the adsorption fate of P on the bamboo charcoal was conducted in lab to better understand the results of the field experiment. The obtained main conclusions are listed as follows:1. During the period from January 2010 to December 2010, the runoff was collected for 23 times in the experiment. The runoff export of nitrogen was 1338g/hm2, while the phosphorus loss was 518.3 g/hm2. Comparatively, both the nitrogen and phosphorus loss in Lei Bamboo stands were not serious. Relatively, P combined readily with soil particles is not easier to be removed from soils than N. In the runoff, N was lost in particle and soluble forms, accounting for 51.73% and 48.27% of the total, however, P was mainly in particular form, accouting for 60.37 % of the total lost P. Compared with runoff loss, the leaching loss of N and P was the dominated loss way from the bamboo stand. The leached ammonium nitrogen, nitrate nitrogen, available phosphorus were 11.35 kg/hm2,36.6 kg/hm2,17.6 kg/hm2, respectively. The long-term fertilization led to nitrogen and phosphorus accumulation in bamboo soils. However, the bamboo soils were thin in layer that resulted easily in nitrogen and phosphorus leaching from the under layer of soils. Therefore, it should be paid much more attentions to N and P leached from the soil layers. The concentration of total soluble N ranged from 0.68 mg/L to 10.62 mg/L, while the total soluble P from 0.16 to 1.47mg/L, those are far higher than the critical concentrations causing the water-body eutrophication. Moreover, the rainfall and fertilization could exert an influence on the N and P concentrations in the runoff. To reduce the risk of N and P entering water, it is necessary to prevent soil nutrients leaching from the agriculture system.2. Ecological grass strip had a significant effect in nutrients control from the Lei Bamboo stands, the least N and P loss throught runoff were 1046.89 g/hm2 and 317 g/hm2. The N and P runoff through the "ecological grass + bamboo charcoal" buffer strip were 1060.83 g/hm2 and 354.36 g/hm2. Those were 1515.03 g/hm2 and 524.34 g/hm2 through the "bamboo + bamboo charcoal" strip. With the control of original bamboo stands, the "ecological grass" treatment could control the nutrients better, however, the bamboo charcoal could not retend the nutrients as efficiently as expected. The use of bamboo charcoal could increase N and P runoff due to the soil disturbance. When using the grass strip, the control efficiency was not high in this study, the interception rate was 29.82% of P and 25.40% of N. The vegetation belt can reduce the runoff significantly through the inteception of particles rather than soluble nutrients. Compared with Cynodon dactylon (N13.49%, P15.33%), ryegrass had a high efficiency in N and P interception (N 28.90%, P 34.06%). However, the ryegrass growth cycle is short, and could only be planted in the first half year. Thus, it is necessary to consider the harvest of ryegrass and continue the sweeding of Cynodon dactylon in cycle. The ecological grass interception effect was the best among the 4 treatments. The untreated bamboo charcoal was used to adsorpt N and P, but it did not show any effect as expected even intensified the runoff of N and P. How to increase the bamboo charcoal in N and P interception in field needs further studies.3. The simulation experiments showed that the amount of P absorbed on the bamboo charcoal increased with the increasing balance P concentration. The absorbed P accounted for a percentage from 40% to 50%. The bamboo charcoal had the largest adsorption rate when the concentration was 10mg/L. Temkin model was best to simulate the isothermal adsorption of P on bamboo charcoal, and Elovich equation was the best to simulate P dynamics adsorption. According to the results of the absorption of P on the bamboo charcoal, the adsorption effect of the bamboo charcoal was not as good as expected. It is very important to clean the bamboo charcoal completely before use or to change the bamboo charcoal for improving the adsorption ability, so that the bamboo charcoal can be used as an effecfient adsorption material in practice.