Abstract
Optimizing phosphorus (P) application to agricultural soils is fundamental to crop production and water quality protection. We sought to relate soil P tests and P sorption characteristics to both crop yield response to P application and environmentally critical soil P status. Barley (Hordeum vulgare L.) was grown in pot experiments with 45 soils of different P status. Half the pots were fertilized at 20kg P ha-1 , and half received no P. Soils were extracted with ammonium lactate, sodium bicarbonate (Olsen P), dilute salt (0.0025M CaCl2 ), and diffusive gradient in thin films. Soil adsorption coefficients were determined using the Freundlich isotherm equation, and the degree of P saturation was determined from both oxalate and ammonium lactate extracted Fe, Al, and P. All soil P analyses showed a nonlinear and significant relationship with yield response to P application, and all analyses manifested a threshold value above which no P response was observed. For the commonly used ammonium lactate test, inclusion of Al and Fe improved prediction of plant-available soil P. The threshold for yield response coincided with the environmentally critical values determined from the degree of P saturation. Results support the conclusion that soil P levels for which no P application is needed also have elevated risk of P loss to runoff.
Highlights
Phosphorus (P) fertilizer is required for optimal crop yield, but there can be conflicting aims between promoting high crop yields and preventing runoff of bioavailable P (Smith, Tilman, & Nekola, 1999)
The objectives of the present study were (a) to relate relative yield response to P application to a range of soil P tests, P sorption characteristics, and P sorption parameters; (b) to determine the environmentally critical soil P status based on soil P tests and P sorption characteristics; and (c) to examine whether certain soil characteristics used in combination with P-ammonium acetate lactate (AL) can improve the precision of P fertilizer recommendations and the estimation of the risk of P runoff
The degree of soil P saturation varied widely: 16–73% for degree of P saturation (DPS) measured in ammonium oxalate extracts (DPS-ox) and 4–59% for DPS measured in ammonium acetate lactate extracts (DPS-AL)
Summary
Phosphorus (P) fertilizer is required for optimal crop yield, but there can be conflicting aims between promoting high crop yields and preventing runoff of bioavailable P (Smith, Tilman, & Nekola, 1999). Have matured and soil P levels have increased, fertilizer P application has decreased. The surpluses in the soil P balance in European countries have substantially decreased since 1990, but more P is still applied than removed with the crops. In Norway, the average P surplus was 26 kg P ha−1 in 1985 (OECD, 2017), but it had decreased to 9 kg P ha−1 in 2014 (Eurostat, 2017). In EU-15 area countries, the average P surplus was only 2 kg P ha−1 in 2014. Efforts to minimize P application rates begin and end with soil testing. Soil testing may be used to predict dissolved P concentrations in runoff (Quinton et al, 2003; Randall et al, 2005; Vadas, Kleinman, Sharpley, & Turner, 2005).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
