Development of yield and nutritive value of timothy in primary growth and regrowth in northern growing conditions

The development of the yield and nutritive value of timothy (Phleum pratense L.) both in the primary growth and in the regrowth were studied at MTT Plant Production Research, a unit of MTT Agrifood Research Finland, in Rovaniemi (66 degrees 35'N) in 1999-2001. The dry matter yield and leaf to stem ratio were measured from the crop samples, and the contents of crude protein and organic matter digestibility of both whole plant samples and leaf and stem fractions were analysed. In primary growth, the most rapid increase of dry matter, 220-240 kg ha(-1) per day, was measured around the beginning of the heading stage. There was a very strong positive correlation between the proportion of stems and the amount of dry matter in the primary yield. The daily growth rate of the regrowth was less than half of that of the primary growth. The fastest decrease, 1 percentage unit per day, in crude protein content was measured at the pasture stage (4-5-leaf stage). During the entire sampling period, the average daily decline in crude protein content in the primary growth of timothy was 0.65 percentage units. The main cause for the rapid decline in crude protein content was the high proportion of stems and their low protein content. In the regrowth, during the last four weeks before the harvest, the average daily decline in crude protein content was 0.28 percentage units. The average decline in organic matter digestibility from early pasture stage to late silage stage was 0.9 percentage units per day. The most remarkable change was noticed at the growth stage of timothy when about the half of stems were heading and it was then that the digestibility decreased by more than one percentage unit per day. The rapid decline in organic matter digestibility was due to the low digestibility of stem matter. The daily change in forage digestibility in the regrowth was very small, on average 0.11%.