模拟降雨下不同农作措施紫色土坡耕地氮磷流失特征

Response of nitrogen and phosphorus losses to different farming treatments in purple sloping farmland under simulated rainfall

为明确不同农作措施下坡耕地氮(N)、磷(P)流失的变化特征,在15°紫色土坡耕地径流小区(长8 m×宽4 m)中,采用60、90和120 mm/h的降雨强度开展模拟降雨试验,对比分析顺坡耕作单施化肥(T1,对照)、顺坡耕作化肥配施有机肥(T2)、横坡垄作单施化肥(T3)3种农作措施小区的N、P流失过程。结果表明:N流失量随产流时间表现为先增大,在达到峰值后保持一定的波动性;P流失量则主要表现为先增大,在达到峰值之后开始下降。在90 mm/h降雨强度条件下,不同农作措施对紫色土坡耕地径流系数的影响不显著(P>0.05),其他处理下各农作措施对径流系数、产沙量及N、P流失量的影响均达到显著水平(P<0.05)。与T1相比,T2、T3均显著减少径流中的N、P流失量,在小降雨强度条件下效果更为明显;T2的N、P削减比例分别为19.36%~62.19%和20.03%~58.01%,T3分别为47.09%~78.45%和50.97%~82.27%。径流系数、产沙量与N、P流失量间均存在极显著的幂函数正相关(R^(2)为0.787~0.893)。研究结果可为优化紫色土坡耕地农作管理提供理论依据。

[Background]Soil erosion has been the most serious environmental problem around the world,which leads to the losses of soil nitrogen(N)and phosphorus(P)in sloping farmland,resulting in dramatically non-point source pollution.Purple soil is widely distributed in southwestern China and is easily eroded owing to its relatively fast weathering rate of purplish parent materials.Sloping farmland is an important grain planting strategy in purple soil area,which usually experiences cross ridge and combined application of organic fertilizer and other agricultural measures to control soil erosion.This work is to determine the effects of different farming treatments on N and P losses in purple sloping farmland.[Methods]Three rainfall intensities(60,90 and 120 mm/h)were adopted to conduct the rainfall simulations on runoff plots(length 8 m×width 4 m)located in a 15°purple sloping farmland.The changed processes of runoff and sediment yield and the characteristics of nitrogen and phosphorus losses were analyzed with three farming treatments including longitudinal ridge with single application of chemical fertilizer(T1,control),longitudinal ridge with chemical fertilizer and organic fertilizer(T2),and cross ridge with single application of chemical fertilizer(T3).One-way ANOVA and regression analysis were used to analyze the relationship between indicators.[Results]1)The losses of N tended to be first increase and then maintained a certain volatility after reaching the peak,while the losses of P increased first and then declined after reaching the peak.2)The different farming treatments showed statistically significant effects on runoff coefficient,sediment yield,and N and P losses under most conditions(P<0.05),except for the runoff coefficient(P>0.05)under the 90 mm/h intensity.3)T2 and T3 significantly reduced the losses of N and P in comparison to T1 under different rainfall intensities,especially in lower rainfall intensity.The N and P reduction ratio were 19.36%-62.19%and 20.03%-58.01%for T2,and were 47.09%-78.45%and 50.97%-82.27%for T3,respectively.4)Both N and P losses showed significantly positive power correlation with runoff coefficient and sediment yield(R^(2) is 0.787-0.893).[Conculsions]The longitudinal ridge with chemical fertilizer and organic fertilizer on the cross ridge with single application of chemical fertilizer can effectively reduce soil erosion and N and P losses in purple sloping farmland.These measures have significant effects on the prevention and control of non-point source pollution in purple sloping farming,and effectiveness of the cross ridge with single application of chemical fertilizer is more stable than the longitudinal ridge with chemical fertilizer and organic fertilizer.