## Theme 13: Plant Improvement

#### Description

Cultivars of timothy (*Phleum pratense* L.) with high N and P use efficiencies are required to reduce costs of production and risks of N and P pollution, and to meet the nutrition requirements of high producing animals. This field study aimed at comparing, (under three N rates) the relationship between DM yield, N uptake, and P uptake of 27 timothy half-sib families, plus the cultivar Champ as a control (Dry matter yield), N and P uptake increased with increasing N rates. Genotypes also differed for DM yield, N and P uptake. For a given DM yield, the genotypes had contrasting N uptake. Similarly, for a given N uptake, there was variability in P uptake. Overall, P uptake was highly correlated to N uptake. We conclude that there is genotypic variability in timothy for N use efficiency, and N and P uptake efficiencies. Our results also confirm that P uptake follows, to a large extent, variations in N uptake as an effect of N rates and genotypes.

#### Included in

Variability for Nitrogen and Phosphorus Uptake among Timothy Genotypes

Cultivars of timothy (*Phleum pratense* L.) with high N and P use efficiencies are required to reduce costs of production and risks of N and P pollution, and to meet the nutrition requirements of high producing animals. This field study aimed at comparing, (under three N rates) the relationship between DM yield, N uptake, and P uptake of 27 timothy half-sib families, plus the cultivar Champ as a control (Dry matter yield), N and P uptake increased with increasing N rates. Genotypes also differed for DM yield, N and P uptake. For a given DM yield, the genotypes had contrasting N uptake. Similarly, for a given N uptake, there was variability in P uptake. Overall, P uptake was highly correlated to N uptake. We conclude that there is genotypic variability in timothy for N use efficiency, and N and P uptake efficiencies. Our results also confirm that P uptake follows, to a large extent, variations in N uptake as an effect of N rates and genotypes.