Campbell Scientific Sentek TriSCAN® Manual v 1.2a - Manual (Page 25)

TriSCAN Manual Version 1.2a
Copyright © 1991 – 2004 Sentek Pty Ltd All rights reserved Page 18
Site Selection
The key to effective soil water and soil volumetric ion content (VIC) monitoring is to select sites which truly
represent irrigation management areas. The same basic site selection principles apply to the full range of
Sentek soil moisture and salinity monitoring devices.
In addition, when monitoring soil solution VIC, consideration of VIC variability in relation to the irrigation
emitter needs to be taken into account.
Many variables influence the spatial distribution of soil water and VIC 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 and soil volumetric ion
content (VIC) readings are taken at different depth levels within the soil profile.”
Note:
If readings are to be used as a basis for scheduling irrigation; managing fertilizer applications or
monitoring salinity, 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
Soil VIC data can provide information about the:
•
Movement of ions within the profile
•
Uptake of ions by the plant or loss to the atmosphere
•
Leaching of salts below the root zone
•
Excessive build-up of salts within the root zone to detrimental levels
Warning:
Do not position TriSCAN sensors at random on your property. Poor site selection will result in
unrepresentative soil moisture and salinity data.
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 is for irrigation and fertilizer to be applied on a
hypothetical “farm average” – similar to traditional broad acre management practices.
Uniform application of irrigation and fertilizer across areas with highly variable soils, nutrient levels and
different levels of crop water use causes significant differences in yield and quality. This creates commercial
losses and environmental harm through increasing problems with rising water tables and increasing salinity.