磷对小麦利用土壤深层累积硝态氮的影响

 【目的】在粮食主产区华北平原，研究磷对小麦利用土壤深层累积硝态氮的影响。【方法】采用15N微区注射技术，布置田间微区试验，将15N标记于110 cm土层处。【结果】在本试验条件下，小麦能够利用注射并扩散于100～120 cm土壤层次的标记硝态氮，3种磷水平的利用率分别为6.8%、16.4%和11.2%;耕层施用磷肥有利于小麦地下部根系发育，根长密度及根干重较不施磷均有增加，提高了小麦对深层硝态氮的利用，耕层适量供磷有利于小麦对土壤剖面深层标记硝态氮的吸收利用。【结论】磷促进小麦根系发育，提高小麦对土壤深层累积硝态氮的利用，过量施磷起抑制作用。

Effects of Phosphorus Fertilizer on the Utilization Ratio of Nitrate Accumulated in Deep Soil Profile by Wheat

【Objective】 The purpose of this study was to indicate the effects of phosphorus application on utilization ratio of nitrate accumulated in deep soil profile by wheat in north China. 【Method】 Field micro-plot experiments and the injection technique of labeled NO3--N were adopted. 【Result】The results showed that, 15N which was injected in 100-120 cm soil profile and diffused in the near layers could be absorbed by wheat with the utilization ratio of nitrate 6.8%, 16.4%, 11.2% in three P levels of P0, P60, P120. The phosphorus applied in the topsoil made the roots grow better with more root length density and dry root weight in it than without phosphorus, by which more deep soil nitrate could be assimilated by wheat and then improved the utilization ratio of nitrate by wheat. 【Conclusion】 Phosphorus application promoted the growth of roots in the deep layers which accelerated the absorption of nitrate accumulated in deep soil profile by wheat, while too much phosphorus fertilizer inhibited the growth of roots of wheat.