土壤供氮能力测试方法的研究——Ⅳ 土壤剖面中的起始NO_3^- —N——可靠的土壤氮素有效性指标

Studies on Methods Determing Soil Nitrogen-supplying Capacities Ⅳ A Reliable Soil N Availability Index: Initial NO_3^--N in Soil Profile

对作物吸氮量直接贡献较大的起始NO^-_3—N,旱区位于30～60cm土层,灌区位于60～100cm土层。播种前0～60cm和0～100cm的起始NO^-_3—N分别是旱区和灌区土壤对冬小麦供氮的可靠指标。不仅如此,一定深度土壤的起始NO^-_3—N还决定了作物吸收氮素的多少。而各种方法测定的可矿化氮反映了土壤潜在的供氮水平。依据一定深度的起始NO^-_3—N划分的土壤氮肥力等级,与两地生产水平相一致。

Initial NO_3^- -N having direct contribution to nitrogen uptake by plants is in 30～60 cm layer in area with no irrigation and 60～100 cm layer in area with irrigation. Initial NO_3^- -N at 0～60cm and 0～100cm depth before seeding are reliable son N availability indeces on drylandsand irrigated lands, respectively. Moreover, the amounts of plant uptake nitrogen are determinedby initial NO_3^- -N at a certain depth. Mineralized nitrogen measured by the other methods can re-flect soil nitrogen-supplying potentials. The soil nitorgen fertility degrees classified by the initialNO_3^- -N levels at a certain depth are in agreement with productive potentials in these two re-gions.