A Geostatistical Analysis of Cropped and Uncropped Soil from the Jimperding Brook Catchment of Western Australia

Abstract

Soil salinity and soil acidity are major problems in many rural areas of Australia. However, by the time these problems are visible at the soil surface, the remedy is lengthy and costly. Soil samples were taken from two neighbouring fields (one on cropped land and the other on uncropped land) in the Jimperding Brook catchment area in the south-west of Western Australia. Parts of this valley already have an obvious salinity problem, as does Jimperding Brook itself. For each field a number of soil attributes were measured on an 11 x 11 regular grid with 6m grid spacing. In addition, for the uncropped field, a further 24 samples were taken at locations other than the grid nodes. Sequential Gaussian simulation techniques were used to analyse the spatial continuity of the grid data and to obtain a picture of the spatial distribution for these attributes in each of the cropped and uncropped cases. Single simulation maps, together with estimation maps resulting from averaging 100 such simulations, were calculated. The differences between the true and predicted values at the additional sample locations were used later to comment on the accuracy of the method used. This analysis can be regarded as a first step in obtaining a profile of the soil salinity, acidity, and general soil condition with regard to future cropping, in this part of the Jimperding Brook catchment.