Water running off the surface of the soil when it rains is not going to be available to crops in drier times. It also takes with it soil and nutrients that would be better left in the field and cause problems once they get into streams and rivers.
We know from our previous research that both woodland and pasture have less impct on water quality than does arable land. This may be linked to the biology of soils in the three land use types. Cranfield University students, Michael Weeks and David Stella have looked at earthworm biomass, microbial biomass and soil organic matter across the three land uses in our 'School Farm' demonstration catchment. Their results are presented below and clearly show that each of these measures is lowest for arable land.
Increasing earthworm numbers, microbial biomass and organic matter is likely to improve the capacity of the cropped area to take up water when it rains, but will also improve the functioning of the soil to the benefit of the crops we are growing for food. We are currently exploring the means of achieving this by reducing tillage intensity and retaining crop residue.
|Earthworm biomass, microbial biomass and organic carbon in arable, pasture and woodland soils in the School Farm catchment. I have converted the three measures to a common index in order to get them all on the same graph.|