Publication Date
1989
Description
Previous work has shown that the N content of a sward could be related to the dry matter accumulation during the course of the regrowth by the following equation : N % = a(Wtb, where W is the weight of aboveground biomass and N % the N concentration of dry matter (Salette & Lemaire, 1981). The coefficient a represents the N % for an aerial biomass of I t/ha, and b characterizes the degree of dilution of N during the regrowth. When b = 0, N % remains constant during the regrowth. If b = I, there is an increase in aboveground biomass without any increase in N uptake. The results obtained by Lemaire & Salette (1984 a, b) and by Lemaire & Denoix (1987) have shown that for a given level of nitrogen nutrition it was possible to determine values for a and b corresponding to a specific dilution curve. These authors have also demonstrated that for a non limiting level of N nutrition it was possible to determine a single N dilution curve, whatever the experimental conditions. This relationship has been determined for different grass swards without variability between genotypes (including different species and natural grass swards) : N % = 4.8 (Wt0•32. A similar relationship with approximately the same values for a and b has been found for a lucerne stand (Lemaire et al. 1986). The generality of such a relationship for optimum nitrogen content has been extended to others species, especially to vegetables (Greenwood et al. 1985). Our objective was to determine how this concept of critical ( or optimal) N % could be used in the analysis of the effect of N fertilisation on aerial biomass production of swards.
Citation
Lemaire, G; Gastal, F; and Salette, J, "Analysis of the Effect on N Nutrition on Dry Matter Yield of a Sward by Reference to Potential Yield and Optimum N Content" (2025). IGC Proceedings (1989-2023). 4.
https://uknowledge.uky.edu/igc/1989/session2/4
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Analysis of the Effect on N Nutrition on Dry Matter Yield of a Sward by Reference to Potential Yield and Optimum N Content
Previous work has shown that the N content of a sward could be related to the dry matter accumulation during the course of the regrowth by the following equation : N % = a(Wtb, where W is the weight of aboveground biomass and N % the N concentration of dry matter (Salette & Lemaire, 1981). The coefficient a represents the N % for an aerial biomass of I t/ha, and b characterizes the degree of dilution of N during the regrowth. When b = 0, N % remains constant during the regrowth. If b = I, there is an increase in aboveground biomass without any increase in N uptake. The results obtained by Lemaire & Salette (1984 a, b) and by Lemaire & Denoix (1987) have shown that for a given level of nitrogen nutrition it was possible to determine values for a and b corresponding to a specific dilution curve. These authors have also demonstrated that for a non limiting level of N nutrition it was possible to determine a single N dilution curve, whatever the experimental conditions. This relationship has been determined for different grass swards without variability between genotypes (including different species and natural grass swards) : N % = 4.8 (Wt0•32. A similar relationship with approximately the same values for a and b has been found for a lucerne stand (Lemaire et al. 1986). The generality of such a relationship for optimum nitrogen content has been extended to others species, especially to vegetables (Greenwood et al. 1985). Our objective was to determine how this concept of critical ( or optimal) N % could be used in the analysis of the effect of N fertilisation on aerial biomass production of swards.
