施肥对浙北平原桑园地表径流中氮磷流失的影响

为了研究浙北平原区桑园氮磷径流流失负荷与肥料流失系数，开展了典型桑园原位定位试验，设置了常规施肥区和不施肥区对照处理，通过一个施肥周期（2年）内的径流氮磷流失量监测分析，研究了桑园氮磷养分的径流流失负荷与肥料氮磷流失率。结果表明，桑园年平均降雨径流系数约为0.253，一次施肥周期内常规施肥区TN和TP累积流失总负荷达到36.13 kg·hm^-2和3.49 kg·hm^-2，其中由施肥引起的N、P养分径流流失量分别达到6.415 kg·hm^-2和1.090 kg·hm^-2，肥料N、P径流流失系数分别为0.744%和3.047%。常规施肥区径流氮流失以可溶态为主，其中NO₃-N和NH₄-N分别占比约38.3%和14.4%；而常规施肥区径流液磷的流失以颗粒态为主，占比约为68.9%。施肥后前期的肥料氮磷养分流失较为严重，且磷流失风险比氮更大，施肥周期内桑园由降雨地表径流引起的氮、磷养分累计流失量与产流次数呈幂函数增加（R²>0.95）。

Effects of Fertilization on Surface Runoff Loss of Nitrogen and Phosphorus from Mulberry in the Northern Zhejiang Plain, China

In 2012 and 2013, the situ experimental plots in mulberry under two different kinds of treatment(control fertilization and farmer''s conventional fertilization) were conducted, and the runoff water in each plot were collected and tested in a period of two years to investigate the law of runoff, the regular pattern and the influential factors of nitrogen and phosphorus losses, and to study the coefficient of fertilizer losses from mulberry in northern Zhejiang plain. The results showed that the annual rainfall runoff coefficient was about 0.253 in mulberry field in northern Zhejiang plain. In those two years, TN and TP cumulative loss load in the conventional fertilization area reached 36.13 kg·hm^-2 and 3.49 kg·hm^-2, of which the N, P nutrient losses of fertilizer reached 6.415 kg·hm^-2 and 1.090 kg·hm^-2, respectively. N, P loss coefficients of fertilizer (the difference of nitrogen or phosphorus loss in the conventional fertilization area and the control area was divided by the total amount of fertilizer application) were 0.744% and 3.047%. Nitrogen loss were mainly in soluble form, in which the NO₃-N and NH₄-N, accounting for about 38.3% and 14.4% respectively; while the phosphorus loss were in particulate form, accounting for about 68.9%. The larger amount of nitrogen and phosphorus nutrient loss, were within the first year of the fertilization period, and the P loss was more serious than N. Within a period of fertilization, the cumulative loss of nitrogen and phosphorus caused by rainfall and the occurrence times of runoff increased with power function(R²>0.95).