The fate of N from dairy cow urine under pasture receiving different rates of N fertiliser

Issue		Agron. Sustain. Dev. Volume 23, Number 7, November 2003


Page(s)		609 - 616
DOI		10.1051/agro:2003038

Agronomie 23 (2003) 609-616
DOI: 10.1051/agro:2003038

The fate of $^{\sf\sl {15}}$ N from dairy cow urine under pasture receiving different rates of N fertiliser

Philippe Leterme, Camille Barre and Françoise Vertes

UMR INRA-ENSAR Sol Agronomie Spatialisation, 65 rue de St Brieuc, 35042 Rennes Cedex, France

(Received 4 July 2001; accepted 1 April 2003)

Abstract - ¹⁵N-labelled urine was used to study the fate of N applied as urine in spring, summer and autumn on ryegrass receiving two different fertiliser rates (100 and 300 kg N $\cdot$ ha^-1 $\cdot$ yr^-1) in Brittany (France). Ammonia volatilisation of labelled urine N was less than 4% and immobilised urine N represented 21-31% of the applied ¹⁵N. Recovery of labelled N in plants ranged from 30 to 65% of N input as urine, showing a decrease in autumn for the highest fertiliser nitrogen treatment. The plant recovery of urine N was relatively high in autumn (49%) when urine was deposited on ryegrass receiving a fertiliser rate of 100 kg N $\cdot$ ha^-1 $\cdot$ yr^-1. Lower N fertiliser regimes can therefore lower the leaching potential of urine N in pastures.

Résumé - Devenir de l'azote des pissats de vache émis sur une prairie recevant différents niveaux de fertilisants azotés. De l'urine de vache laitière marquée au ¹⁵N a été utilisée pour étudier le devenir de l'azote urinaire apporté au printemps, en été et à l'automne sur un ray-grass anglais fertilisé à 2 doses d'azote (100 et 300 kg N $\cdot$ ha^-1 $\cdot$ an^-1). La volatilisation d'ammoniac est toujours inférieure à 4 % de l'azote apporté et l'azote immobilisé dans le sol sous forme organique représente 21 à 31 % de l'apport. Le coefficient réel d'utilisation de l'azote par les plantes varie de 30 à 65 %, diminuant à l'automne pour le traitement 300. Le CRU de l'apport d'automne demeure cependant relativement élevé pour la prairie ne recevant que 100 kg N $\cdot$ ha^-1 $\cdot$ an^-1 (49 %). Cela peut conduire à un risque de lessivage de l'azote urinaire plus faible dans les régimes de fertilisation modérée.

Key words: urine / grassland / fertiliser rate / leaching / ¹⁵N

Mots clés : pissat / prairie pâturée / fertilisation / lessivage / ¹⁵N

Corresponding author: Philippe Leterme leterme@agrorennes.educagri.fr

Communicated by Gérard Guyot (Avignon, France)

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