多年生黑麦草草地矿质氮淋溶与径流流失的关系

以人工放水模拟冲刷试验,研究多年生黑麦草草地土壤矿质氮素淋溶和径流流失的关系。当硝态和铵态氮肥用量分别达到5000kgN/km²,冲刷强度为1mm/min,冲刷时间为50min时,观测氮素径流流失,于48h后检测土壤矿质氮动态。结果表明,坡度为25°、20°、15°、10°和5°土壤,铵态氮径流流失量分别为97.3、87.9、79.0、57.1和50.4kg/km²,分别占施氮量的1.9%、1.8%、1.%、1.1%和1.0%。铵态氮淋溶深度仅达到60cm,其淋溶量占施氮量的55.3%～8.1%,且随着坡度的增大淋溶量逐渐减少。硝态氮随着径流的流失量分别为575.4、330.3、282.6、140.1和91.0kg/km2,分别占施氮量的11.5%、6.6%、5.7%、2.8%和1.8%。硝态氮淋溶与土壤水分入渗同步,随着坡度的降低淋溶深度则逐渐增加,硝态氮主要在0～0cm土层累积,其累积量介于209～3433kg/km2之间,占施肥量的41.9%～8.7%,而在0～105cm土层累积量则介于723～2521kg/km²之间,占施氮量的14.5%～50.3%。

The Relationship of Mineral Nitrogen Leaching in Perennial Ryegrass Land with Its Runoff Loss

The soils fertilized by 5000kgN/km2 ammonium and nitrate fertilizers,are scoured by water with lmm/min flux,after water-scoured 48 hours,the available N in soil profile are surveyed.The water-scoured result shows as fellows.The ammonium fertilizer losses in runoff,loss amounts in 25°，20°，15°，10°and 5° slope land,are 97.3,87.9,79.0,57.1 and 50.4 kg/km2 respectively, which account as 1.9%,1.8%,1.6%,1.1% and 1.0% of ammonium fertilizer.The ammonium fertilizer infiltrating amounts in 60cm depth of soil profile account as 55.3%～86.1%.The nitrate losses in runoff,the loss amounts in different slope gradients are 575.4,330.3,282.6,140.1 and 91.0 kg/km2 respectively,which account as 11.6%,6.6%,5.7%,2.8% and 1.8% of nitrate fertilizer.The nitrate infiltrating depth is same as water within 48 hours.The accumulation amounts of nitrate fertilizer in 0～60cm and 60～105cm soil profiles are 2096～3433,723～2521 kg/km2 respectively,accounting for 41.9%～68.7% and 14.5%～50.3% of nitrate fertilizer.