Campbell Scientific Sentek EasyAG Installation Guide v 3.0 - Manual (Page 10)

Site Selection
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Mulch can improve the infiltration rate of the soil, reduce water run-off, encourage root growth near the soil
surface and increase the soil water holding capacity over time, through the accumulation of soil organic
matter, and reduce soil temperature.
Oil spraying
Oily substances on leaves reduce water use by temporarily closing stomata. An example of this is mite
control in citrus.
Fertilizer management
In order to ensure that no nutrients are deficient, fertilizer applications are normally based on soil and/or leaf
sample analyses. The degree of precision varies from a rough averaging approach to precision farming
where sample points are matched to requirements using satellite tracking technology. Healthy crops require
more water and have different nutrient dynamics to crops that have been stunted or diseased through
inefficient fertilizer management.
Pest/disease management
Good pest/disease management keeps the crop protected and in good health, sustaining its potential growth
and transpiration rates. Infestations can result in lower than normal water uptake.
Irrigation System
The effectiveness of an irrigation system to deliver water affects crop water use. Variations in irrigation
sy stem pressure, flow and water distribution uniformity cause variations in irrigation application. This affects
root zone wetting patterns and therefore crop water use.
The preceding crop water use factors should be taken into account when matching your irrigations to areas
of similar crop water use. These areas are then represented by soil water monitoring sites and the data
collected at these sites is used for irrigation scheduling purposes.
Water Quality
The source and constituents of irrigation water impact on osmotic potential and hence plant water uptake.
Water quality can vary both within and between seasons and between water sources. Sodic waters can also
affect soil structural properties, reducing water infiltration rates.
A general view of macro scale zone selection
Macro zone selection is used to identify the total number of required zones and their locations on your
property. A macro zone comprises areas of similar crop water use. The aim of good site selection is to
select a monitoring site that reflects changes in soil water content and crop water use trends.
The representative data gained from monitoring sites is used to schedule irrigations over a larger defined
area. This area (or macro zone) may be an entire field, or a sub-section of a field, where irrigation is applied
during a watering shift.
As an irrigator, you want to replenish the soil water used by plants for growth and transpiration. So, it is
important to understand the many factors which affect crop water use or transpiration and how these factors
may vary on your farm.
A primary goal of good irrigation management is to match irrigations to areas with similar crop water use,
within the limits of your irrigation system flexibility. This consideration will ultimately determine how many
monitoring sites you will need and where you should locate them.
The diagrams on the following pages show an example of how ‘factors that affect crop water use’ can be
used to determine macro zones. Consult your local soil specialist for further information on the soils at your
site.