SOIL

Soil is one of factors that makes a locality-associated condition variable. It’s physical, chemical, and biological properties in relation to the environmental factors e.g., climate, management, etc., influence the soil’s productive capacity. A high crop yield is the result of the favorable interactions of soil properties and environmental factors. An unfavorable soil properties such as high or low pH can affect plant growth.

In assessing the crop suitability in an area; texture, pH, and organic matter are usually used indices. These data may not be enough in explaining frequent deviations from broadly accepted principles. For examples, clay soils are suitable for lowland rice because the soil can hold more water; but te are sandy soils which are known to be as productive for rice as clays soil, if not more. It is, therefore, imperative that a more comprehensive characterization of the soil be done for better understanding of result of field experiments.

Physiographical Data

Information on physiography or topography of the land is as important as the soil data themselves. In many instances, very slight gradations in soil properties cannot be detected by ocular observations of the soils alone. Soil surveyors can only delineate soil unite boundaries within certain limits of scales, after which they are not ble to include all the existing variations. Pedologist normally deduce possible changes in the soil properties by looking for changes in slope conditions.

Measurement of the slope gradient, description of the shape of the slope, and the relative position of the experiment on the particular slope can provide considerable information from which interpretation and extrapolation of experimental result could be based. Slope gradient is indicative of external drainage and subsequently, susceptibility to erosion. It can be measured with two meter sticks a plastic tubing (Raymundo, 1978).

The shape of the slope can indicate te relative hydrologic conditions. On convecx slopes, the lowest section of the slope is steepers, and comparatively has less ponding potentials of the paddies than the middle or the top position of the slope. A straight slope has comparatively uniform ponding potential on the lowest sections, and the least in the highest section of the slope. In unplad areas, the lowest section of the convex slope is more subject to erosion while te lowest section in a cancave slope normally becomes a depositional area. Shapes of slopes are readly discernible by ocular evaluation.