Macro-organic matter (roots and partially decomposed plant debris retained on a 0·25 mm mesh sieve) was measured in soils under various swards. Under a grazed perennial ryegrass/white clover sward, sown on arable land, macro-organic matter in the top 15 cm of soil rose steadily in the first 8 years to 15·8 t/ha, but subsequently declined. Under arable cropping there was great variation with crop and season. Under grass, most of the macro-organic matter accumulated in the top 2 cm of soil, particularly during the first 3 or 4 years. More macro-organic matter was found under perennial ryegrass/white clover than under cocksfoot/white clover swards.

After 3 years under grass macro-organic matter accounted for 10% of the total soil carbon, and represented about half the increase in soil carbon.

Half, or less, of the nitrogen which accumulated in soil under grass was in the macroorganic matter fraction. The differences between swards which received no N fertilizer and those which received 940 kg/ha over 3 years was small, 16–40 kg N/ha respectively for cut and frequently grazed swards. The ratio of C:N in macro-organic matter under different swards averaged 22:1.

Soils and plants can absorb more S than is brought down in rain (Johansson, 1960). Much of the S absorbed from the air by light sandy soils (Mann, 1955) during the autumn, winter and spring is lost by leaching and only that absorbed by soil during crop growth can be used. The crop can also absorb atmospheric S directly through the leaves; the amounts may be larger than soils supply when crops have a leaf-area index larger than 1 (Olsen, 1957; Spedding, 1969).