Meta‐analysis of grass ley response to phosphorus fertilization in Finland

Abstract

AbstractStudies have shown that yield responses of grass leys to phosphorus (P) fertilization vary considerably and initial soil test P (STP) does not always predict such variation. To identify the sources of variation in dry‐matter (DM) yield responses to P, we used a meta‐analysis to review quantitatively 38 Finnish field experiments on various soil types and growth conditions and to develop yield‐response models. The major sources of variation in the yield responses to annually applied P were soil type, soil acidity (for organic soils), initial STP and control yields fertilized with nitrogen (N) and potassium (K). According to Mitscherlich‐type exponential models, the maximum yield increases due to P fertilization in the low‐STP class were 18% over the control on mineral soils and 28% on organic soils. However, only about 40% of the variation in yield could be attributed to annual fertilizer P applications. Control yields explained about 25% of variation in yield responses to P fertilization, and P addition became less efficient with increasing control yields, which were associated with rising N rates. While applied P leads to infrequent or small yield responses on mineral soils, other practices to increase grass yields should be prioritized, including optimal N fertilization. On moderately acidic organic soils that show clearly lower P responses than do similar but less acidic soils, liming should be the first step to increase yields. Moreover, the models derived in this work indicate that revising P fertilizer recommendations in Finland would avoid unnecessary application at non‐responsive STP levels.