[Effects of poplar-amaranth intercropping system on the soil nitrogen loss under different nitrogen applying levels].

Characteristics of soil nitrogen loss were investigated based on field experiments in two types of poplar-amaranth intercropping systems( spacing: L12 m×5 m,L22 m×15 m) with four N application rates,i.e.,0( N1),91( N2),137( N3) and 183( N4) kg·hm-2. The regulation effects on the soil surface runoff,leaching loss and soil erosion were different among the different types of intercropping systems: L1 L2 L3( amaranth monocropping). Compared with the amaranth monocropping,the soil surface runoff rates of L1 and L2decreased by 65.1% and 55.9%,the soil leaching rates of L1 and L2with a distance of 0.5 m from the poplar tree row decreased by30.0% and 28.9%,the rates with a distance of 1.5 m decreased by 25.6% and 21.9%,and the soil erosion rates decreased by 65.0% and 55.1%,respectively. The control effects of two intercropping systems on TN,NO3--N and NH4+-N in soil runoff and leaching loss were in the order of L1L2L3. Compared with the amaranth monocropping,TN,NO3--N and NH4+-N loss rates in soil runoff of L1 decreased by 62.9%,45.1% and 69.2%,while the loss rates of L2 decreased by 23.4%,6.9% and 46.2% under N1( 91 kg·hm-2),respectively. Higher tree-planting density and closer positions to the polar tree row were more effective on controlling the loss rates of NO3--N and NH4+-N caused by soil leaching. The loss proportion of NO3--N in soil runoff decreased with the increasing nitrogen rate under the same tree-planting density,while that of NH4+-N increased. Leaching loss of NO3--N had a similar trend with that of NH4+-N,i.e.,N3N2N1N0.