HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Duru, M. Search for Related Content PubMed Articles by Duru, M. Agricola Articles by Duru, M. Related Collections Forage Management Grazing Management Nitrogen

Nitrogen Management

Simplified Nitrogen Assessment of Orchardgrass Swards

UMR INRA-ENSAT ARCHE, Chemin de Borde Rouge, BP27, 31326 Castanet Tolosan, France

^* Corresponding author (mduru{at}toulouse.inra.fr)

Received for publication September 15, 2003. A sward N index (N_i) based on herbage N concentration [N_a in g kg^–1 dry matter (DM)] and sward mass (DM Mg ha^–1) was proposed previously for management of N fertilizer: N_i = 100 x N_a/48DM^–0.32. For the sake of simplification, we developed and evaluated a method based only on the N concentration of approximately the upper 7 cm of sward (N_us). Twenty-one treatments of pure or dominant orchardgrass (Dactylis glomerata L.) swards, covering a wide range of N fertilizer rates, regrowth periods, sites, and years, were used to establish a relationship between conventional (N_i) and simplified (N_us) sward N status. Detailed studies were conducted on a subset of treatments to determine the N distribution along the length of the leaf and down the sward's vertical profile. Analysis of N distribution among leaf segments for orchardgrass swards showed that N_us did not change over time with respect to N_i once there were about three leaves per tiller. Two close linear relationships between N_us and N_i were established, one for samplings made after three leaves had appeared on a tiller [about 500 degree-days (DD) after defoliation of the sward] (r² = 0.92; n = 62; SE = 2.8) and the other before this stage (r² = 0.94; n = 12; SE = 3.3). We concluded that the N_us method is good enough to be used for assessing N sward status for a large range of defoliation regimes, without measurement of standing herbage mass: N_i = 2.94N_us – 20.59 and N_i = 2.28N_us – 12.07, respectively, after and before 500 DD.

Abbreviations: DD, degree-days (0°C base temperature) • DM, dry matter • LAI, leaf area index • N_a, actual sward nitrogen concentration (g N kg^–1 DM) • N_i, sward nitrogen index (varying from 40 to 120) • N_us, nitrogen concentration (g N kg^–1 DM) of approximately the upper 7 cm of sward