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Phosphorus−nitrogen relationships of forage grasses in response to mineral phosphorus fertilization

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Bélanger G., Ziadi N., Lajeunesse J., Jouany C., Virkajarvid P., Nyiraneza J., Sinaj S
Project Improving the knowledge-base and infrastructure to enhance the efficiency of nutrient use in agriculture and to reduce the negative impact of agriculture on the environment
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Original article (peer-reviewed)

Journal Field Crop Research
Volume (Issue) 204
Page(s) 31 - 41
Title of proceedings Field Crop Research


The sustainable P management of grassland ecosystems require a better understanding of the effect of Pfertilization on the growth of grassland swards and the relationship between shoot P and N concentra-tions with the overall goal of developing improved methods of predicting P requirements of grasslandswards. Our objectives were to determine the importance of P supply during the primary growth inspring, to analyze the optimal relationship between shoot P and N concentrations for timothy (Phleumpratense L.) and multi-species swards under a wide range of P nutrition, and conditions of soil and cli-mate, and to confirm for grassland swards the decrease in the N:P ratio during crop growth previouslyreported for annual crops. Experiments with varying rates of P fertilization were conducted for two tofive consecutive years at sites with timothy swards in Canada (Lévis, Normandin, Charlottetown, andQuebec) and Finland (Maaninka), and at sites with multi-species swards from long-term P fertilizationexperiments in Switzerland (Les Verrières) and France (Ercé). Dry matter (DM) yield, and N and P con-centrations were measured on four dates with one-week intervals from the vegetative to late headingstages of development during primary growth. Our results (i) indicate that a P deficiency mostly affectsthe early season growth of grassland swards corresponding to shoot biomass less than approximatively1 Mg DM ha−1, (ii) confirm the optimal relationship between shoot P and N concentrations for timothyand multi-species swards but with variations of the relationship with the level of N nutrition and betweentimothy and multi-species swards, and (iii) confirm for grassland swards the decrease in the N:P ratioduring the primary growth and the close relationship of the N:P ratio to shoot biomass.