Bioaccessibility and bioavailability of subsoil P

在我们目前的研究中，我们发现，磷是丰富的底土生物孔隙系统，但在散装底土生物可及性。后一种结论的证据来自缺失的底土磷酸盐和土壤水之间的同位素平衡。该项目不是为了检验以下假设：（i）磷酸盐的δ 18 O特征表明生物孔壁中的P比散装土壤中的P具有更高的生物可利用性，（ii）底土根可以容易地从矿物中获得P，（iii）植物磷酸盐至少部分地反映了土壤磷酸盐的δ 18 O特征，（iv）当表层土壤养分和水分缺乏时，底土磷吸收的程度增加，并且（v）在R-SWMS中可以实现热点地区更高的磷可及性，允许更精确地估计从底土吸收的P。为了实现这些目标，我们将应用18 O同位素交换实验之间的土壤磷酸盐和水，进行放射性和稳定同位素示踪实验与土壤和三重标记磷灰石（44钙，33磷，18 O），以及养分收购的根的数值模拟。

In our current studies we found that P is enriched in subsoil biopore systems but not bioaccessible in the bulk subsoil. Evidence for the latter conclusions was derived by missing isotope equilibria between subsoil phosphates and soil water. This project was no designed to test the hypotheses that (i) the delta18O signature of phosphates indicate higher bioaccessibility of P in biopore walls than in the bulk soil, (ii) subsoil roots may readily acquire P from minerals, (iii) plant phosphates reflect at least partly the delta18O signature of soil phosphates, (iv) the degree of subsoil P uptake increases when the surface soil is deficient in nutrients and water, and that (v) higher P-accessibility in hotspots can be implemented in R-SWMS, allowing for estimating P uptake from the subsoil more precisely. To achieve these goals we will apply 18O isotope exchange experiments between soil phosphates and water, perform radioactive and stable isotope tracing experiments with soil and triple-labeled apatite (44Ca, 33P, 18O) as well as a numerical modeling of nutrient acquisition by the roots.