The RSPB is attempting to establish heathland and acid grassland on 158 ha of arable land at Minsmere, ultimately to benefit two species of rare breeding birds, the stone curlew Burhinus oedicnemus and the woodlark Lullula arborea. An initial study of the arable soils was carried out to assess their suitability for the establishment of Calluna heathland and acid grassland. Selected chemical properties of the arable soils were compared to (1) existing heathland and (2) some old-field successions on former arable land, both adjacent to the arable fields to assess the magnitude of the change required. Three soil factors were identified as potential constraints; the arable soils had a much greater soil pH and higher concentrations of exchangeable calcium and extractable phosphorus than heathland soils, almost certainly from previous lime and fertilizer additions. These factors will almost certainly have to be reduced in order to establish heath or acid grassland communities on the arable soils at Minsmere. In the initial stages the RSPB followed the prescription adopted by MAFF for the re-establishment of heathland on arable soils within the Breckland Environmentally Sensitive Area. This involved an arable cropping regime designed to reduce 'soil fertility'. At Minsmere, linseed, spring and winter barley, and cereal rye were planted, and inorganic nitrogen and potassium fertilizers applied. The aim was to improve crop yield, increase nutrient uptake and hence remove more nutrients from the system. The crops were harvestable in most years, although yields were lower than those found under normal farm management. The cropping removed more nutrients from the system than measured inputs, but there have been no appreciable reductions in soil pH or available nutrients. There was a slight indication that the exchangeable calcium concentrations may be declining after seven years, brit no reduction in soil pH was found. Accordingly, cropping must be viewed as a medium to long-term option (> 7 :years) for impoverishing the arable soils at Minsmere. (C) 1998 Elsevier Science Ltd. All rights reserved.
