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采用田间试验方法,研究了杨树-苋菜间作系统,即株行距2 m×5 m(L1)和2 m×15 m(L2)在0(N0)、91(N1)、137(N2)和183(N3)kg·hm-2施氮水平下的土壤氮素流失特征.结果表明:不同施氮水平对地表径流量、淋溶量和土壤侵蚀量的控制效果均为L1>L2>L3(单作苋菜);L1、L2地表径流量分别比L3降低65.1%、55.9%;L1、L2距林带0.5 m处淋溶量比L3降低30.0%、28.9%,距林带1.5 m处淋溶量比L3降低25.6%、21.9%;L1、L2土壤侵蚀量分别比L3降低65.0%、55.1%.对地表径流和淋溶损失中TN、NO3--N、NH4+-N流失量的控制效果均为L1>L2>L3;常规施氮(91 kg·hm-2)水平下,L1地表径流中TN、NO3--N、NH4+-N流失量较L3分别降低62.9%、45.1%、69.2%,L2较L3分别降低23.4%、6.9%、46.2%;杨树间作密度越大、距离林带越近,对土壤NO3--N、NH4+-N的淋溶损失削减作用越强.同一间作密度下,随着施氮量的增加,地表径流中NO3--N流失比例减少,NH4+-N流失比例增加;淋溶流失中NO3--N、NH4+-N浓度变化趋势一致,均为N3>N2>N1>N0.
A field experiment was conducted to study the effects of poplar-amaranth intercropping system on the relationships between 0 (N0), 91 (N1), 137 (N2) and 2 × 15 m (L2) The results showed that the control effects of different nitrogen application rates on surface runoff, leaching amount and soil erosion amount were all in the order of L1> L2> L3 (N> 3) kg · hm-2 And the surface runoff of L1 and L2 was reduced by 65.1% and 55.9% respectively than that of L3. The leaching amount at 0.5 m from L1 and L2 was reduced by 30.0% and 28.9% respectively at L3 and L3, L3 decreased by 25.6% and 21.9%, respectively.The soil erosion of L1 and L2 decreased by 65.0% and 55.1% respectively than that of L3.The control effects of TN, NO3 - N and NH4 + -N on surface runoff and leaching loss were all L1 > L2> L3. Compared with L3, the loss of TN, NO3 - N and NH4 + -N in surface runoff decreased by 62.9%, 45.1% and 69.2% respectively under the conventional nitrogen application (91 kg · hm-2) L3 decreased by 23.4%, 6.9% and 46.2%, respectively. The greater the interplanting density was, the closer it was to the forest belt, the stronger the reduction effect on the leaching loss of NO3 - N and NH4 + -N was. With the increase of nitrogen application rate, the proportion of NO3 - N loss in surface runoff decreased and the proportion of NH4 + -N loss increased. The concentrations of NO3 - N and NH4 + -N in the runoff showed the same trend, all of which were N3> N2> N1> N0.