Diversity of Soil Characteristics in Field and Its Relation with Landform Spatial Pattern at Agrotechnopark Koleberes, Cianjur

Abstract

Soil mapping in detail scale needs a high intensity of observation and costly. To decrease the cost, the mapping usually done using an approach of delineation of soil forming factors into homogeneous sets. This approach is based on an assumption that if soil forming factors are homogeneous then the soil characteristics will also homogeneous. However various survey experiences indicated that at sloping areas, soil characteristics still vary although soil forming factors show a high homogeneity. The aim of this research is to study soil characteristics observed from boring with a high observation intensity and to search for a spatial relation between soil characteristics and classification with spatial distribution of landform at a slopping areas. Materials of this research comprised contour map, geology map, existing soil map and soil data covering profile description and its of physic and chemical data. GIS software (Arc View GIS 3.3) was used for spatial analysis of landform. In this research, landform are delineated based on an 1:1000 contour map considering the concept of “Model Diagram of Nine Land Surface” of Dalrymple et. al. (1968; in Darmawan, 1987). Field characteristics of soil were obtained from borings taken at the close distances along slope transects. Observation conducted at some slope transects across various landforms. Soils on research location formed from parent material which is relatively homogeneous under the influence of the same climate, organism and times. Meanwhile relief/ topography shows a high heterogeneity, with differences that even happened at a narrow space. This heterogeneity is reflected by existence of various landform i.e. convex-rather flat-upper slope, straight-flat to rather steep middle slope, concave-rather steep lower slope, etc. Soil field characteristics obtained from boring observation at close distances show very high variations as shown by variation in composition and depth of horizon A and B, soil colour, texture and consistency. This phenomenon could affect the soil classification at family and series level. Toposequently, from upper slope (convex) through the mid slope (straight), to the lower slope (concave) had a tendency to have more complex horizon composition. This phenomenon was due to the dominant process of erosion at the upper slope, and deposition at the lower slope.