Managing Soil Variability
Sources of Variability
Differences in crop growth and yield are attributable to many factors. Soils
develop over geologic time, and are influenced not only by the parent material
from which they are derived, but also by climate, biota, and topography.
Physical characteristics of soils such as soil texture, color, and strength are not
easily modified. Farming practices may have limited effect on soil permeability
and structure. Soil chemical properties such as cation exchange capacity are not
However, management decisions such as cropping patterns, fertilization
history, and irrigation practices can influence residual nutrient levels, pH, and
salinity. Certainly, each of the above factors may contribute to the variability in
crop growth that we observe in the field.
Variable Rate Application
Today’s technology allows us to vary the rate of crop inputs during an
application job. Once the variability of a soil parameter is identified and
mapped, our agronomists prepare a recommendation. The recommendation is
converted to a controller file. The controller file contains the rate information
for specific locations or zones within the field. Paired with a GPS device, the
controller determines the current location of the application rig, identifies the
rate to be applied, and sends a signal to the pump, belt, or auger to distribute
the right amount of product.
Characterizing Soil Variability
Soil sampling and laboratory analysis are an excellent way to identify variability
in soil nutrient levels, soil pH, and salinity. Sampling more intensively increases
the data used to develop the recommended rates of crop inputs. With our grid
sampling service, sample locations are recorded using GPS technology, and soil
samples are usually collected every 2 ½ acres. We offer a variety of analytical
packages to meet your needs. Once the data is returned from the laboratory,
mapping software is utilized to display field variability for each of the measured
soil test parameters. To simplify the interpretation of this field variability, a
second map is displayed which shows the agronomic interpretation of this data.
Please contact your local Crop Production Services' field representative for more information.