Bioaccessibility of phosphorus in the subsoil (SubsoilP)

植物可能从底土中吸收10%至80%的磷需求，但作物序列管理对底土磷的影响形式和可获得性目前尚不清楚。该项目的目的是（i）量化具有不同生物孔隙系统的中央田间试验（CeFiT）的不同底土隔室中的磷储量和结合形式，（ii）阐明蚯蚓洞穴对底土层磷吸收的贡献，以及（iii）测试土壤和植物磷酸盐的δ 18 O特征作为追溯其起源和停留时间的新工具的可行性。样品取自根际，散装土壤，地下洞穴衬里和前根通道的中央田间试验（CeFiT）和中央微观实验（CeMiX）。磷的形式和浓度的特点是连续的P提取程序，高分辨率元素映射，和31 P-NMR光谱。利用33 P和18 O标记的磷酸盐进行同位素吸收和交换研究，以评估生物孔隙中磷的吸收速率和磷酸盐在土壤中的停留时间。

Plants may take up between 10 and 80 % of their P demand from subsoils, but the forms and accessibility of subsoil P as affected by crop sequence management are currently hardly understood. This project aims at (i) quantifying the P stocks and binding forms in different subsoil compartments of the central field trial (CeFiT) with varying biopore systems, (ii) elucidating the contribution of earthworm burrows to P uptake from subsoil horizons, and (iii) testing the feasibility of the δ18O signature of soil and plant phosphates as a novel tool for tracing back their origin and residence time. Samples are taken from rhizosphere, bulk soil, earthworm burrow linings and former root channels both from the central field trial (CeFiT) and central microcosm experiment (CeMiX). The P forms and concentrations are characterized by sequential P extraction procedures, high-resolution element mapping, and 31P-NMR spectroscopy. Isotope uptake and exchange studies using 33P and 18O labelled phosphate are used to evaluate P uptake rates from biopores and phosphate residence time in soil.