Factors influencing herbage yield

Deep soils are more fertile than shallow soils (shallow is defined here as less than 30 cm). 

In Britain the further north the farm is, the colder the annual temperature and the shorter the growing season for grass and clover. 

Crompton (1958) made the point that on the western seaboard of Britain it is only in exceptional years that even the January temperatures fall below 6°C, and some grass growth is therefore possible throughout the year, whereas at the summit of Ben Nevis (1342 m above sea level) even the July mean temperature does not normally rise to 6°C and there is no growing season at all for ordinary plants. 

Hunter and Grant (1971) demonstrated that with some grass cultivars yield declined by approximately 2% for every 30.5 m increase in altitude, and that the development of flowering was delayed by 1.3 days per 30.5 m increase in altitude. 

It is generally accepted that below 6°C grass is unlikely to grow, and this is known as the cardinal temperature. Alberda (1965) stated that at temperatures above 11 °C grass growth is independent of increase in temperature and that under optimal nutritional conditions growth is then determined by light intensity. 

---