Benefits from long-term ecological research; some examples from Rothamsted.

Field experiments began at Rothamsted, Hertfordshire, in the 1840s, with eight of the original experiments today still examining which elements present in farmyard manure are essential for plant growth, and in what quantity. Data from these and other long-term experiments are reported, with sections on: soil acidification (changes in soil pH over 100 yr, and acidfying inputs); effect of soil pH on soil properties of (P fixation, release of cations, and effects of liming); effect of soil pH on flora; other inputs to soil (temporal changes in cadmium content, temporal changes in polynuclear aromatic hydrocarbons, and sulphur cycling); and the effects on soils of changing land use. The prerequisites and merits of long-term ecosystem research are summarised. Such research has been essential in this case to estimate small but consistent long-term changes in soil composition and their effects on crop growth and composition. -P.J.Jarvis