Soil test phosphorus and cumulative phosphorus budgets in fertilized grassland.

Messiga, A.J., Ziadi, N., Jouany, C., Virkajärvi, P., Suomela, R., Sinaj, S., Bélanger, G., Stroia, C., and Morel, C. (2015). "Soil test phosphorus and cumulative phosphorus budgets in fertilized grassland.", AMBIO, 44(2), pp. 252-262. doi : 10.1007/s13280-015-0628-x  Access to full text

Abstract

We analyzed the linearity of relationships between soil test P (STP) and cumulative phosphorus (P) budget using data from six long-term fertilized grassland sites in four countries: France (Ercé and Gramond), Switzerland (Les Verrières), Canada (Lévis), and Finland (Maaninka and Siikajoki). STP was determined according to existing national guidelines. A linear-plateau model was used to determine the presence of deflection points in the relationships. Deflection points with (x, y) coordinates were observed everywhere but Maaninka. Above the deflection point, a significant linear relationship was obtained (0.33 < r2< 0.72) at four sites, while below the deflection point, the relationship was not significant, with a negligible rate of STP decrease. The relationship was not linear over the range of STP encountered at most sites, suggesting a need for caution when using the P budget approach to predict STP changes in grasslands, particularly in situations of very low P fertilization. Our study provides insights and description of a tool to improve global P strategies aimed at maintaining STP at levels adequate for grassland production while reducing the risk of P pollution of water.

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