| Agricultural non-point source pollution makes an important contribution to the pollution problems of Dianchi lake, including the unreasonable application of large amount of pesticides and fertilizers, which can not only cause the erosion of nutrients such as nitrogen and phosphorus from the soil, change the soil nitrogen and phosphorus structure itself, but also affect the cycle of nitrogen and phosphorus of biogeochemstry. The study of the effects of fertilizers and pesticides on the change of soil nitrogen and phosphorus storage in Dianchi lake watershed is necessary to provide basic data for the current non-point source pollution control.The different cultivation in the farmlands of Chai river within watershed of Dianchi lake were selected as the study area in order to understanding the basic condition of nitrogen and phosphorus storage and availability while different utlization intensity in different planting patterns. Based on the first-stage field investigation, laboratory analysis and reference farmland comparison, we selected the floriculture greenhouses to conduct the field experimentation. All the experimentation were carried out in three different treatment sets: fertilizer treatment group, pesticide treatment group, pesticide and fertilizer compound treatment group, and non-treantment used as referent group. The effects of fertilizers and pesticides on soil nitrogen and phosphorus storage were supposed to studied in this research. The main results are given as follows:(1) The field investigation showed that the results from open farmland took the least usage of fertilizer, N 45.35 kg/Mu·a, (1Mu= 0.0667 hectare), P2O5 24.3 kg/Mu·a, farmyard manure 320 kg/Mu·a; and pesticides were used for three times, and two kinds of insecticides, three kinds of microbicides, three kinds of herbicide during July to December, 2015. It was floriculture greenhouses that N 100.4 kg/Mu-a, phosphate fertilizer 57 kg/Mu·a, farmyard manure 900 kg/Mu·a were used, and pesticides were used every 4-5 days during growing seasons, and 6 kinds of insecticides,15 kinds of microbicides were utlized. Vegetable greenhouse applied nitrogen 200 kg/Mu·a, phosphate fertilizer,70 kg/Mu·a, farmyard manure 600 kg/Mu·a, and pesticides were used every 7-10 days, which included 3 kinds of insecticides,17 kinds of microbicides,2 kinds of plant growth regulator.(2) In the depth of 0～20 cm soil of open farmland, the average of total nitrogen content was 1207.34 mg/kg, the average of alkali-hydrolyzale nitrogen content was 137.28 mg/kg, the average of total phosphorus content was 816.84 mg/kg, the average of available phosphorus content was 41.83 mg/kg, every indexes content gradually reduce with the increase of depth. In the 0-20 cm soil of floriculture greenhouses, total nitrogen content, alkali-hydrolyzale nitrogen content, total phosphorus content and available phosphorus content were 1648.85 mg/kg,165.18 mg/kg,1430.87 mg/kg,357.49 mg/kg on the average level, all the content gradually reduce with the increase of depth. In the depth of 0-20 cm soil of vegetable greenhouse, the average of total nitrogen content was 2091.42 mg/kg, the average of alkali-hydrolyzale nitrogen content was 171.42 mg/kg, the average of total phosphorus content was 1381.91 mg/kg, the average of available phosphorus content was 307.15 mg/kg, content gradually reduce with the increase of the depth. Overall, the soil nitrogen and phosphorus availability in 0-20 cm and 20-40 cm soil represents obvious differences, the effectiveness of nitrogen shows floriculture greenhouses> outdoor field >vegetable greenhouses, while the effectiveness of phosphorus shows floriculture greenhouses >vegetable greenhouses >open field.(3) The pesticides trentment showed that soil ammonium nitrogen content, available phosphorus content, microbial carbon content, microbial nitrogen content and the ratio of microbial carbon nitrogen were significantly influenced, among which soil ammonium nitrogen content and available phosphorus content, microbial carbon, nitrogen content were significantly decreased, the ratio of microbial carbon and nitrogen increased.(4) The fertilizer treantment represented that soil total nitrogen content, alkali-hydrolyzale nitrogen, nitrate nitrogen, ammonium nitrogen content, total phosphorus content, available phosphorus content, microbial carbon content, the ratio of microbial carbon and nitrogen in the depth of 0 to 40 cm were affected. In this control group, soil total nitrogen content, alkali-hydrolyzale nitrogen, nitrate nitrogen, total phosphorus content, available phosphorus content, microbial carbon content as well as the ratio of microbial carbon and nitrogen were significantly increased, soil ammonium nitrogen content was significantly decreased.(5) The compound treatment of fertilizers and pesticides appeared that ammonium nitrogen content, available phosphorus content, microbial carbon content, microbial nitrogen content,the ratio of microbial carbon and nitrogen were mainly influenced in the depth of 0 to 40 cm soil, and ammonium nitrogen content, microbial carbon content, microbial nitrogen content were significantly decreased, meanwhile, available phosphorus content, the ratio of microbial carbon and nitrogen were significantly increased.In summary, the current fertilizer use patterns had significant effect on soil nitrogen and phosphorus pool, soil nitrogen and phosphorus pool of greenhouse was significantly higher than that of open field, but no significant differences were observed between the different greenhouses; application of chemical fertilizers significantly affected total nitrogen, alkaline hydrolysis nitrogen, nitrate nitrogen, ammonium nitrogen, total phosphorus, available phosphorus, microbial biomass carbon in the soil. Pesticides mainly affected the contents of ammonium nitrogen, available phosphorus, microbial biomass carbon, soil microbial biomass nitrogen in the soil. Meanwhile the interaction of chemical fertilizer and pesticide improved the nitrification rate of soil, increased soil microbial biomass carbon and nitrogen ratio, and the effective state content of nitrogen and phosphorus, so it also increased the risk of erosion nitrogen and phosphorus. |
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