Campbell Scientific Sentek EnviroSCAN Access Tube Installation Guide - Manual (Page 6)

Sit e Selection
© Sent ek Pt y Lt d Page 3
Site Selection
The key to effective soil moisture monitoring is to select monitoring sites which truly represent irrigation
management areas. The same basic site selection principles apply to the full range of Sentek soil moisture
monitoring devices. Many variables influence the spatial distribution of water across an area of land. These
variables and their impact on site selection are discussed in more detail below.
What is site selection?
A site is defined here as:
“The location of the access tube within a field or irrigation shift, where soil water readings are taken at
different depth levels within the soil profile.”
Note:
If readings are to be used as a basis for scheduling irrigations over larger defined
areas, it is imperative that monitoring sites are representative of these areas.
Soil moisture data can provide information about the:
• Quality and depth of irrigations
• Levels of soil moisture retention
• Depth of the crop root zone
• Impact of weather and rainfall events on an area
Warning:
Do not select irrigation scheduling sites at random on your property. Poor site
selection will result in soil moisture data that is unrepresentative of soil water
changes and crop water use in that field.
Site selection is carried out in two stages:
• Macro zone selection
• Micro zone selection
Relationship between macro and micro zones in the field
Traditional practice within the field and across the whole farm has been for irrigation to be applied on a
hypothetical “farm average” – in a similar way to traditional broad acre management practices.
Uniform application of irrigation across areas with highly variable soils and different levels of crop water use
causes significant differences in yield and quality, creating commercial losse s and environmental harm
through increasing problems with rising water tables and increasing salinity.
If different soil types are ignored in terms of their different irrigation scheduling requirements, crop setbacks
or failures may occur.
Macro zone selection defines the number of zones on a property where the amount of timing of irrigation
applications can be specifically tailored to match soil and crop variability – a macro zone comprises areas
with similar crop water use.
Crop water use is governed by many factors such as soil properties, water quality, weather patterns and type
of irrigation system. These factors need to be considered when defining the macro zones on your property
and are described in the following pages.