Effects of temperature and nitrogen supply on the growth of timothy (Phleutn pratense L.)

Timothy was grown in controlled environments with day/night temperatures of 18.5/10° C. and 29.5/21° C, with and without extra nitrogen. High temperatures hastened all stages of development after inflorescence initiation. Anthesis occurred after 48 days when N was added and after 52 days without N. Anthesis did not occur until after 68 days at the lower temperatures, with or without N. Largest yields of leaves, stems and stubble were produced at all growth stages at the lower temperatures with N. This treatment gave the highest crop growth rate, which increased almost linearly with time. The lower temperatures with N gave many more and longer stems and more inflorescences than any other treatment. With N and high temperatures, there was no increase in crop growth rate after inflorescence emergence. Temperature had little effect on growth when no N was provided. With no added N, crop growth rate was retarded and increased very little after inflorescence initiation. Herbage produced at high temperatures had the lower percentages of water-soluble carbohydrates and digestible dry matter, but had the higher percentages of most minerals. N increased the percentage content of most minerals. Weights of stubble and of water-soluble carbohydrates in the stubble, and the numbers of stem bases and tillers, were larger at the lower temperatures, and were usually larger with added N in both temperature regimes. Nitrogen decreased the percentage content of carbohydrates in the stubble. Large haplocorms were produced at the low temperatures, but none developed at the high temperatures, indicating less carbohydrate storage. The results partly explain the vigorous growth of timothy in the cool, temperate regions of Europe and North America, and the small dry matter production, lower nutritional value of the herbage, and lack of persistence in the warm southern regions where rainfall is adequate.