MOBILIZATION OF PHOSPHATE IN DIFFERENT SOILS BY RYEGRASS SUPPLIED WITH AMMONIUM OR NITRATE
MOBILIZATION OF PHOSPHATE IN DIFFERENT SOILS BY RYEGRASS SUPPLIED WITH AMMONIUM OR NITRATE
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DOI：
10.1007/bf00010600
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发表时间：
1992-02-01
期刊：
影响因子：
4.9
通讯作者：
JUNGK, A
中科院分区：
文献类型：
--
作者：
GAHOONIA, TS;CLAASSEN, N;JUNGK, A
研究了植物诱导植物根系附近土壤pH值变化对土壤磷的动员作用。黑麦草幼苗生长在小容器中，用30 μ m的尼龙筛网将根与土壤隔开，根毛可以穿透，但不能穿透根。采用两种土壤，一种是主要与钙结合的含磷土壤，另一种是主要与铁和铝结合的含磷土壤。施用氨氮或硝态氮可引起植物引起的土壤pH变化。植株生长10 d后，将土壤切成与屏幕上已发育的根垫平行的薄层，测定土壤pH和残磷。利用根际土壤磷素耗竭剖面评价土壤磷素的动员。在铵态氮的作用下，根表土壤pH值降低了1.6个单位，在硝态氮的作用下，根表土壤pH值升高了0.6个单位。这些变化延伸到离根表面1到4毫米的距离，这取决于土壤类型和施氮的来源和水平。与零氮处理相比，在luvisol处理中，随着nh4诱导的pH降低，P的动员增加，而no3诱导的pH升高没有影响。相反，在草甘醇中，NH4营养引起的pH降低没有影响，而NO3引起的pH升高明显增加了土壤p的动员。由此可见，在草甘醇中，磷酸钙通过酸化溶解，而在草甘醇中，吸附的磷酸盐通过配体交换被动员。
Mobilization of soil P as the result of plant-induced changes of soil pH in the vicinity of plant roots was studied. Seedlings of ryegrass were grown in small containers separating roots from soil by a 30-mu-m meshed nylon screen which root hairs could penetrate but not roots. Two soils were used, a luvisol containing P mainly bound to calcium and an oxisol containing P mainly bound (adsorbed) to iron and aluminum. Plant-induced changes of soil pH were brought about by application of ammonium-or nitrate-nitrogen. After plants had grown for 10 d the soil was sliced in thin layers parallel to the root mat which had developed on the screen, and both soil pH and residual P determined. Mobilization of P was assessed by P-depletion profiles of the rhizosphere soil.Soil pH at the root surface decreased by up to 1.6 units as the result of ammonium N nutrition and it increased by up to 0.6 units as the result of nitrate N nutrition. These changes extended to a distance between 1 and 4 mm from the root surface depending on the type of soil and the source and level of nitrogen applied. In the luvisol, compared to zero-N treatment, P mobilization increased with the NH4-induced decrease in pH, whereas the NO3-induced pH increase had no effect. In contrast, in the oxisol a similar pH decrease caused by NH4 nutrition had no effect, whereas the pH increase caused by NO3 increased markedly the mobilization of soil P. It is concluded that in the luvisol calcium phosphates were dissolved by acidification, whereas in the oxisol adsorbed phosphate was mobilized by ligand exchange.