Yield response to soil test phosphorus in Switzerland: Pedoclimatic drivers of critical concentrations for optimal crop yields using multilevel modelling

Juliane Hirte; Walter Richner; Barbara Orth; Frank Liebisch; René Flisch

doi:10.1016/j.scitotenv.2020.143453

Yield response to soil test phosphorus in Switzerland: Pedoclimatic drivers of critical concentrations for optimal crop yields using multilevel modelling

Sci Total Environ. 2021 Feb 10;755(Pt 2):143453. doi: 10.1016/j.scitotenv.2020.143453. Epub 2020 Nov 9.

Authors

Juliane Hirte¹, Walter Richner², Barbara Orth², Frank Liebisch³, René Flisch²

Affiliations

¹ Agroscope, Agroecology and Environment, Water Protection and Substance Flows, 8046 Zurich, Switzerland. Electronic address: juliane.hirte@agroscope.admin.ch.
² Agroscope, Agroecology and Environment, Water Protection and Substance Flows, 8046 Zurich, Switzerland.
³ Agroscope, Agroecology and Environment, Water Protection and Substance Flows, 8046 Zurich, Switzerland; ETH Zurich, Department of Environmental Systems Sciences, Institute of Agricultural Sciences, Crop Science Group, 8001 Zurich, Switzerland.

PMID: 33199000
DOI: 10.1016/j.scitotenv.2020.143453

Abstract

Phosphorus (P) management in agroecosystems is driven by opposing requirements in agronomy, ecology, and environmental protection. The widely used maintenance P fertilization strategy relies on critical concentrations of soil test P (STP), which should cause the lowest possible impact on the environment while still ensuring optimal yield. While both soil P availability and crop yields are fundamentally related to pedoclimatic conditions, little is known about the extent to which soil and climate variables control critical STP. The official P fertilization guidelines for arable crops in Switzerland are based on empirically derived critical concentrations for two soil test methods (H₂O-CO₂ and AAE10). To validate those values and evaluate their relation to pedoclimatic conditions, we established nonlinear multivariate multilevel yield response models fitted to long-term data from six sites. The Mitscherlich function proved most suitable out of three functions and model fit was significantly enhanced by taking the multilevel data structure into account. Yield response to STP was strongest for potato, intermediate for barley, and lowest for wheat and maize. Mean critical STP at 95% maximum yield ranged among crops from 0.15-0.58 mg kg^-1 (H₂O-CO₂) and 0-36 mg kg^-1 (AAE10). However, pedoclimatic conditions such as annual temperature or soil clay content had a large impact on critical STP, entailing changes of up to 0.9 mg kg^-1 (H₂O-CO₂) and 80 mg kg^-1 (AAE10). Critical STP for the AAE10 method was also affected by soil pH. Our findings suggest that the current Swiss fertilization guidelines overestimate actual crop P demand on average and that site conditions account for large parts of the variation in critical STP. We propose that site-specific fertilization recommendations could be improved on the basis of agro-climate classes in addition to soil information, which can help to counteract the accumulation of unutilized soil P by long-term P application.

Keywords: Critical concentrations; Long-term field trials; Mitscherlich function; Multivariate analysis; Nonlinear mixed models; STP.