| Popis: |
The Palouse region of eastern Washington is characterized by complex rolling hills with high erosion susceptibility. Various aspect and slope classes along with different soil types also create complex patterns in soil fertility and crop productivity. Division of fields into different units and addressing each unit as a separate management zone has been gaining importance in recent years. Landscape modeling is one of the tools that helps define management zones based on the spatial variability of the soil and topographic characteristics. In addition to comprehensive models, there is an increasing demand for simpler techniques to assist planners with field scale, day-to-day land management. The objective of this study was to develop a simple landscape model within a geographical information systems (GIS) framework to evaluate the effects of spatial variability of topographic factors on soil genesis. For this purpose, a commercial wheat farm was chosen as the research site and a digital elevation model (DEM) of the site was prepared. Landscape parameters such as slope, aspect and tangential curvature were calculated. GIS overlay of these values were georeferenced and combined with other data layers such as soil maps and air photos. Soil samples were collected on three different transects and representative pits were opened for further evaluation of soil properties. Depth to E horizon was measured for all sampling locations. Results indicate that spatial distribution of E horizon can be estimated by surface curvature, slope and aspect. Study also shows that contrasting soils that are in close proximity to each other, too close to be separated on conventional soil maps, can be detected with the help of landscape parameters. Big map units that extend over several hillslope positions can be further divided into smaller units to receive separate agricultural management based on soil, water relationships defined by these landscape parameters. |
