Soil and Agricultural Land Classification in County Londonderry

Abstract

An assessment of the value of a conventionally prepared soil series map as the physical basis of agricultural land classification is made for part of County Londonderry in Northern Ireland. An original soil map was made on a field scale of i :io 560, and seven selected soil series were shown to be significantly different in six of the eight soil properties measured on sub-soil samples. The field area was chosen because the soil series were representative of much of Northern Ireland and it was hoped that 'bench-mark' relationships might be established between soil properties of these series and the gross margins from agricultural enterprises. These were calculated for oats, barley, potatoes and livestock production, as well as for a composite 40'5 hectare (ioo acre) farm unit, and the soil series were again shown to have significantly different gross margins for all enterprises except oats. Five stepwise multiple regressions were carried out on the gross margins from these enterprises against the values of the eight soil properties of sub-soil samples from each farm. The soil properties accounted for a considerable proportion of the variation in gross margins, up to 43 per cent in the case of the composite farm unit, and all eight soil properties were limiting on one or more of the enterprises. The influence of soil on agricultural profitability was notable, but the spatial variation of the relation- ship did not conform with the boundaries of the soil series units. The latter had been proved not significantly different in two soil properties which were limiting on gross margins. The disadvantages, therefore, of using soil series maps for agricultural land classification are recognized. LAND classification defines the value or quality of land for any one type of use. One aim in preparing maps and schemes of land classification is to enable land-use planners to allocate land among its various possible uses for the maximum satisfaction of the whole community. This paper is concerned only with the agricultural use of land and does not attempt to consider competition from forestry, or from recreational, water conservational, urban or industrial uses. In particular, an attempt is made to evaluate the effects of several soil variables on the profitability, and indirectly on the current value, of agricultural land in the