耕层施磷对土壤剖面深层累积NO3——N运移及后效的影响

 【目的】在华北平原,研究前茬小麦耕层施磷对土壤深层累积NO3--N运移及后效的影响。【方法】采用15N微区注射技术,耕层设3个不同的施磷水平,布置田间微区试验,将15N标记于110 cm土层处。【结果】在该试验条件下,小麦收获后标记15N在土壤中的残留量为P60处理＜P120处理＜P0处理,且发生垂直运移,向上层土壤运移了50 cm,向下移动了70 cm,累积峰出现在120～140 cm土层,较标记位置下移了30 cm。玉米收获后, 15N主要分布在100～180 cm土层,累积峰在小麦季基础上又向下移动了20 cm。玉米能利用前茬残留于土壤深层的15N,P0、P60、P120处理15N的利用率分别为1.2%、2.5%、2.2%。前茬施磷对后作玉米下层根系发育仍有促进作用,增加了80～150 cm土层根长密度和根干重比例,提高了施磷处理对残留15N的利用率。【结论】前茬耕层施磷仍影响土壤深层累积NO3--N后效,促进后作玉米中下层根系发育,提高深层氮素利用率,进而减少其在土壤剖面中的残留。

Effects of Phosphate Fertilizer Applied to Topsoil on the Movement and Residual Effect of Nitrate Accumulated in Deep Soil Profile

Objective] The purpose of this study was to indicate the effects of phosphate fertilizer applied to topsoil on the movement and residual effect of nitrate which was accumulated in deep soil profile in North China Plain. Method] The injection technique of labeled NO_3~--N was adopted in a field micro-plot experiment. Three phosphate fertilizer treatments were desigred at each experimental site. The labeled NO_3~--N was injected in 110 cm soil profile. Result] At this condition, the distribution of residual amount of ~(15)N in each soil profile after wheat harvest was: P60