Land evaluation studies for grass production systems in the uplands of north-east Scotland

• Main Author: Riley, H. C. F.
• Published: University of Aberdeen 1977
• Subjects: 338.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.470518

Existing systems of land classification in Britain were outlined, and the need for more emphasis on the particular problems of hill areas was established. Previous studies in the Department of Soil Science at Aberdeen have considered many aspects of land capability classification for both forestry and grass production, but, since the majority have dealt with the former use, it was decided to concentrate on grass production in this case. Features of hill land in Britain, and their limiting effects upon the types of farming system sustainable, were described, Ways of increasing hill sheep productivity were reviewed, and the importance of improved grassland at periods of acute nutritional imbalance was stressed, Environmental and management factors affecting grass productivity in hill areas were then reviewed. The applicability of previous workers' findings to the soils of the north-east Highlands as a whole was appraised, and it was considered desirable to obtain information about upland grass productivity over a wider area, particularly in relation to soils recently reclaimed from moorland. Sites were established on good quality grass swards in areas representative of three of the most extensive soil associations in northeast Scotland, according to experimental designs incorporating factors of soil association, altitude, major soil group and NPK fertilizer treatment. Most emphasis was put upon environmental factors in the first season's field design, whilst more attention was subsequently paid to fertilizer treatments. aSoils analysis revealed few differences, in chemical properties between soil associations for members of the same major soil group, but large differences between soils of different major groups, There were, in particular, much higher subsoil reserves of phosphorus and calcium in brown earths than in podzols, though in the surface horizons such differences had been obscured by recent fertilizer treatment, Vegetation analysis during the first season confirmed that most sites were of comparable botanical composition, but prompted the deletion of certain atypical swards from subsequent field designs, The climatic conditions of the experimental seasons were characterised in relation to temperature and rainfall, and were considered to be somewhat atypical of the long-term means in both respects. In view of this the second year's field experiment is being continued for a further season, and it is hoped that the results may serve to test the validity of the present findings in relation to a less favourable season, The results of both years' field experiments showed that, despite the shortness of the growing season, considerable yields of herbage dry matter could be obtained on both soil groups in all areas, together with responses to nitrogen fertilizer that approached those which might be expected under lowland conditions. Nevertheless brown earths were found to consistently outyield podzols, with appreciable amounts of nitrogen fertilizer being required to make up the difference. The overall yield response to nitrogen was linear for both soil groups up to a level of 175 kg/Ha.N. Dry matter responses to phosphorus and potassium fertilizer were either small or absent, though this may have been due in part to the influence of residual fertilizer effects, particularly on the recently reclaimed sites. Recoveries of all fertilizer materials were variable, but within the ranges quoted as typical for lowland areas, Consideration was given to the amounts of phosphorus and potassium fertilizer required to maintain reserves under various management regimes, even in the absence of specific DM responses to their use. The soils' inherent potassium supplying power, in particular, was investigated. Various multivariate techniques were used to investigate the nature of the variables controlling grass productivity within and between major soil groups, including correlation, factor analysis and multiple regression of both individual variables and factor scores derived from factor analysis of soil and site data. A land capability classification was proposed>making use of the productivity information obtained, together with observations about the physical and environmental factors affecting the utilisation of such production. A scheme of capability mapping at a reconnaissance level v/as suggested, and a broad categorisation of present land use was determined for an area ;-of 800 km2 in the north-east Highlands, as a preliminary indication of the areas involved. Finally, an attempt was made, using information derived from many sources, to calculate the secondary store-lamb output which might be possible from given quantities of primary production, assuming two different levels of flock management, Estimates were then made of the proportions of specific land units which would be required to support the higher level of output thus proposed.