Relationship between climatic factors and the dry matter production of swards of different composition at two altitudes

The growth of a timothy sward, a timothy/white clover mixture and a multi‐grass/white clover mixture were compared and related to climatic factors at two sites of different altitudes. Temperature and radiation had a greater effect on sward growth than did species composition or management. If the reproductive and vegetative growth periods were studied separately, then more than 90% of the variation in yield could be explained by temperature and radiation. During spring reproductive growth, yields per unit increment of temperature or radiation were 2–3 times higher than during summer vegetative growth. Spring growth was affected more by temperature than by radiation and the lower yields at the higher altitude were also related to lower temperatures.