A study of the soils and agronomy of a high country catchment

Abstract

This study was undertaken to research the principles and practices behind increased pasture productivity on Longslip Station, Omarama. A range of landscape - soil - climate - plant systems were identified, then analysed and the legume responses measured. By isolating cause and effect and appreciating the driving variables of each system, lessons learnt could be reliably and objectively transferred to the rest of the farm. Extrapolation to the balance of the property (15,150 ha) permitted immediate large-scale development and engendered confidence to lending institutions, Lands Department, catchment authorities and ourselves. Soil (land) cannot be well managed and conserved unless it is mapped reliably and its characteristics measured and interpreted by skilled observers (Cutler, 1977). Soil resource surveys, and their interpretation, are an essential ingredient of rational resource evaluation and planning. This thesis is a figurative and comparative survey and study of the soil catenary bodies, resident vegetation, legume establishment and pasture production characteristics of a 400 hectare catchment, in relation to, and as influenced by soil landscape unit, slope component, altitude, aspect and time. The inherent diversity in landform, soil properties and vegetation communities in a single catchment in the high country has not previously been fully studied or appreciated. This has lead to blanket recommendations for fertilizer, seed and management regimes both within and between properties and even regions. This study reports on the diversity of, yet predictable change in soil properties with slope position (upper, middle and lower) aspect and altitude in terms of both soil physical properties e.g. soil depth and water holding capacity and soil chemical properties such as pH, BS%, %P, %S, %N and %C. The composition of the resident vegetation and its differential response to oversowing and topdressing and subsequent change through time is reported and discussed. Finally an epilogue gives an insight into the problems and frustrations of farming practices in the high country from a motivation and personal perspective and political point of view that it is essential to come to terms with.