Land use for England and Wales: evaluation of management options to support 'good ecological status' in surface freshwaters

This paper analyses historic records of agricultural land use and management for England and Wales from 1931 and 1991 and uses export coefficient modelling to hindcast the impact of these practices on the rates of diffuse nitrogen (N) and phosphorus (P) export to water bodies for each of the major geo-climatic regions of England and Wales. Key trends indicate the importance of animal agriculture as a contributor to the total diffuse agricultural nutrient loading on waters, and the need to bring these sources under control if conditions suitable for sustaining 'Good Ecological Status' under the Water Framework Directive are to be generated. The analysis highlights the importance of measuring changes in nutrient loading in relation to the catchment-specific baseline state for different water bodies. The approach is also used to forecast the likely impact of broad regional scale scenarios on nutrient export to waters and highlights the need to take sensitive land out of production, introduce ceilings on fertilizer use and stocking densities, and controls on agricultural practice in higher risk areas where intensive agriculture is combined with a low intrinsic nutrient retention capacity, although the uncertainties associated with the modelling applied at this scale should be taken into account in the interpretation of model output. The paper advocates the need for a two-tiered approach to nutrient management, combining broad regional policies with targeted management in high risk areas at the catchment and farm scale

Forms of phosphorus transfer in hydrological pathways from soil under grazed grassland

Phosphorus (P) from soil can impair the water quality of streams and lakes. We have studied the forms and pathways of its movement from soil to water using 1-ha plot lysimeters, managed as grazed grassland for 12 months in temperate South-west England. The water flow through three pathways, namely (i) surface plus interflow to 30 cm (on undrained soil), (ii) surface plus interflow to 30 cm (on a mole and tile drained soil), and (iii) mole and tile drains (to 85 cm), were gauged. Samples of water from each path were treated with various combinations of 0.45-mu m filtration and sulphuric acid-persulphate digestion and molybdate reaction, to determine the different forms of P. The total P (TP) concentration was greatest in the surface plus interflow to 30 cm paths (means 232 and 152 mu g l(-1)), whereas the mean concentration in the drainage to 85 cm was 132 mu g l(-1). This reflects the substantial enrichment of the Olsen-P extracts from the surface horizons, as extracts from the 0-2 cm layer were 10-fold more than below 45 cm. In all paths, the dissolved P comprised the greatest proportion of the P transferred, with dissolved reactive P being the dominant form. Draining land reduced the transfer of TP by about 30% (approximate to 1 kg(-1) ha(-1) year(-1)), because it can be sorbed as it flows through soil to drains. All these concentrations could cause eutrophication in surface waters