不同施肥对雷竹林径流及渗漏水中氮形态流失的影响

Effects of fertilization on nitrogen loss with different forms via runoff and seepage under Phyllostachy praecox stands

雷竹经营过程中化肥的大量施用,是产区水体污染的主要原因之一,养分管理技术可有效控制面源污染。为了探明减量施肥和有机肥施用对雷竹不同氮形态流失的影响,2012年在浙江省临安市雷竹产区设置了4种施肥处理:对照(CK);常规施肥(CF);减量无机(DI);减量有机无机(DOI),试验于5月18日、9月7日、11月9日分别施用肥料总量的40%,30%和30%,施肥后均进行浅翻,深度5 cm左右。通过建立径流场和土壤渗漏水收集装置,同时在试验田附近布置量雨筒,观察2012年不同氮形态浓度及流失负荷随降雨量的动态变化。研究结果表明:不同施肥处理径流水硝态氮、水溶性有机氮(WSON)以及颗粒态氮的浓度分别在3.82—6.82 mg/L、0.89—1.85 mg/L和0.89—1.83 mg/L,其占总氮的百分比分别为60.9%—68.2%、16.0%—18.1%和15.1%—21.6%。不同施肥处理渗漏水中硝态氮、铵态氮及WSON的浓度分别在26.2—92.5 mg/L、0.50—6.42 mg/L和6.57—12.6 mg/L,其占总氮的百分比分别为75.8%—82.9%、1.50%—6.36%和11.2%—20.6%。不同施肥处理径流水的氮总流失负荷,减量无机和减量有机无机相对于常规施肥来说减少了46.9%和23.1%;不同施肥处理的渗漏水的氮总流失负荷,减量无机和减量有机无机相对于常规施肥来说减少了19.1%和52.1%,可见减量施肥和减量有机无机减少氮流失的效果显著。

Heavy winter mulching to increase soil temperature and winter fertilization are widely used techniques for intensive management of Phyllostachys praecox forests to increase bamboo shoot production and economic return for landowners in subtropical China. The application of excessive mineral fertilizer has resulted in serious water pollution.The object of this study was to ascertain effects of reducing inorganic fertilizer rate or applying organic fertilizer on reducing the loss loads of different forms of nitrogen under Phyllostachy praecox stands by conducting a field experiment in main production area of Lin＇an city, Zhejiang province.Four treatments were respective 1 ） control with zero fertilizer （CK）, 2） conventional fertilizer （CF） at the rate of N ＋ P2O5 ＋ K20 = 850 ＋ 337.5 ＋ 337.5 kg/hm2 provided with 2250 kg/hm2 of compound fertilizer and 1110 kg/hm2 of urea, 3 ） decreasing inorganic fertilizer （DI） at the rate of N ＋P2 O5 ＋ K20 = 510 ＋ 337.5 ＋337.5 kg/hm2 provided with 2250 kg/hm2 of compound fertilizer and 376 kg/hm2 of urea, and 4） decreasing organic and inorganic fertilizer （DOI） at the rate of N＋P2Os＋K20=510＋259.8＋165.4 kg/hm2 provided with 554 kg/hm2 of urea and 46400 kg/hm2 of pig manure. Fertilizer were separately applied in May 18th, September 7th and November 9th with respective 40% ,30% and 30% of total amount of fertilizer, and then plowed into soil at the depth of 5 cm.Water samples from runoff and leaching water were collected by special devices, totally 16 runoff water samples and 10 seepage water samples were collected around the year 2012. It was shown that the concentrations of different forms of nitrogen actuallyaffected by rainfall, especially for particulate nitrogen （PN） in the runoff water. The concentrations of nitrate nitrogen （NO^-N）, water-soluble organic nitrogen （WSON） and PN in the runoff water were at the range of 3.82-6.82 mg/L, 0. 89-1.85 rag/L, and 0.89-1.83 mg/L, respectively, which accounting for 60.9%-68.2%, 16.0%-18. 1%, and 15.1%-21.6% of total N loss, respectively.The concentrations of NO3-N, ammonium nitrogen （NH4-N） , and WSON in the seepage water were 26.2-92.5 mg/L, 0.50-6.42 mg/L and 6.57-12.6 mg/L, respectively, which accounting for 75.8%-82.9%,1.50%-6.36% and 11.2%-20.6% of total N loss, respectively.Nitrate N was among the largest loss both in runoff water and seepage water.The loss loads of total N in the runoff water respectively decreased by 46.9% and 23. 1% for DI and DOI treatments compared with CF, and the corresponding data for seepage water were 19. 1% and 52. 1%.In conclusion, decreasing inorganic fertilizer or decreasing organic and inorganic fertilizer play a remarkable role on reducing the loss loads of different forms of N under Phyllostachy praecox stands suggesting that reducing inorganic fertilizer rate and applying organic fertilizer was the useful practice to decrease the N loss.