Subsoils—a sink for excess fertilizer P but a minor contribution to P plant nutrition: evidence from long-term fertilization trials

Abstract Background The phosphorus (P) stocks of arable subsoils not only influence crop production but also fertilizer P sequestration. However, the extent this is largely unknown. This study aimed to (i) determine sequestration with soil depth, (ii) analyze speciation after long-term fertilization, and (iii) compare tests in predicting yields. We analyzed four trials Germany a depth 90 cm. Treatments received either mineral or organic P, combination both, for 16 113 years. determined inorganic pools using sequential extraction, 31 nuclear magnetic resonance (NMR) X-ray absorption near edge structure (XANES) spectroscopy. In addition, we applied three tests, double-lactate (DL), calcium acetate lactate (CAL), diffusive gradients thin films (DGT). Results results suggested that plants are capable mobilizing from deeper layers when there negative budget topsoil. fertilization mostly showed insignificant effects on pools, which were most pronounced topsoil, 1.6- 4.4-fold increase labile (P i ; resin-P, NaHCO 3 –P ) 0- 1.9-fold o , NaOH–P fertilization. differences mainly controlled by site-specific factors, e.g., properties management practice rather than When modeling yield response Mitscherlich equation, obtained highest R 2 ( = 0.61, < 0.001) among topsoil DGT . fit became less incorporating subsoil. Conclusion conclude if has good supply, majority taken up originates method mechanistic surrogate plant uptake. Thus, basis optimization recommendation add as much required sustain yields low necessary prevent harmful leaching excess P.