Timothy grass (Phleum pratense) is a perennial grass originally from northern Europe. It is a tall grass species which can grow up to 1.5 m at the reproductive stage. It performs well in heavy, poor sandy soils, and is resistant to cold weather and dry conditions. As other grass species it requires adequate soil nitrogen for optimal growth.
Timothy and other cool season grasses generally respond well to nitrogen fertilization, with 20 to 25 kg of herbage dry matter produced yearly per kg of nitrogen/hectare. Response is related to the original nitrogen availability in the soil, with a greater response in more deficient areas.
The timeline of the nitrogen application also affects the quality of the sward. When applied later into the growing season it leads to more vegetative growth compared to tall, more hardened stems earlier in the season. This is an important consideration depending on the region since vegetative growth is desirable for quality, although it may also lead to more winter damage.
It is important then to optimize fertilization rates such that they not only increase herbage dry matter production, but also result in forage that withstands the cold season while still maintains adequate quality. As with other grasses, nitrogen fertilization increases not only the crude protein content of the plant but also its concentration in nitrates, which could be potentially toxic to ruminants.