Agriculture Reference
In-Depth Information
Chapter 2
Heterogeneity in Fields: Basics of Analyses
Hermann J. Heege
Abstract
Sustainable and economical farming needs precise adaptation to the
varying soil- and plant properties within fields. Consequently, farming operations
have to be adjusted to this in a site-specific way.
An important question is, on which spatial resolution or cell size within a field
these adjustments should be based. It is reasonable to expect that this depends on the
spatial variations of the respective soil- or crop properties. Consequently, it is shown
how the cell sizes needed can be derived from semivariances and its complement
functions, the covariances.
Once thus suitable cell sizes are known, they should not be exceeded on any site-
specific stage, whether this is sampling, mapping or the operations of the farm
machinery.
Keywords
Cell-sizes • Kriging • Resolution • Semivariance • Semivariogram
2.1
Variation and Resolution
A traveller attentive to agricultural land will notice that uniform fields are not the
rule (Fig.
2.1
). This becomes especially obvious to farming experts, who look more
closely at soils and crops.
Many soil- and crop properties can vary within fields, such as
e.g.
•
texture (content of sand, silt, loam or clay) and pH of topsoil and subsoil
•
soil content of organic matter, of water and of various minerals
•
slope and orbital orientation of the soil
