Interception of residual nitrate from a calcareous alluvial soil profile on the North China Plain by deep-rooted crops: A ~(15)N tracer study

摘要

~(15)N-labeled nitrate was injected into different depths of an alluvial calcareous soil profile on the North China Plain. Subsequent movement of NO_3~--N and its recovery by deep-rooted maize (Zea mays L.) and shallow-rooted eggplant (Solarium melongena L.) were studied. Under conventional water and nutrient management the mean recoveries of ~(15)N-labeled nitrate from K~(15)NO_3 injected at depths 15, 45, and 75 cm were 22.4, 13.8, and 7.8% by maize and 7.9, 4.9, and 2.7% by eggplant. The recovery rate by maize at each soil depth was significantly higher than by eggplant. The deeper the injection of nitrate the smaller the distance of its downward movement and this corresponded with the movement of soil water during crop growth. Deeper rooting crops with high root length density and high water consumption may therefore be grown to utilize high concentrations of residual nitrate in the subsoil from previous intensive cropping and to protect the environment.