Campbell Scientific Sentek TriSCAN® Manual v 1.2a - Manual (Page 26)

TriSCAN Manual Version 1.2a
Copyright © 1991 – 2004 Sentek Pty Ltd All rights reserved Page 19
If different soil types are ignored in terms of their different irrigation scheduling requirements and nutrient
management, crop setbacks or failures may occur. This effect is displayed in the aerial photograph of a
citrus orchard (Photo 1).
Photo 1. Variable growth due to uniform management across variable soil types
Macro zone selection defines the number of zones on a property where the amount and timing of irrigation
and fertilizer applications can be specifically tailored to match soil and crop variability. A macro zone thus
comprises areas with similar crop water and nutrient requirements and salinity characteristics.
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.
Micro zone selection determines the position of access tubes in relation to the crop and irrigation system.
Micro zone selection considers the:
•
areas of root zone and canopy spread
•
water distribution uniformity (sprinkler pattern)
•
moisture patterns of drip irrigation
•
surface, topographic and soil anomalies
The consideration of these factors will help you find the best representative position or site for access tube
placement within the macro and micro zones.
Macro and micro zone selection is described in greater detail in the following pages. If you require further
information, consult your Sentek reseller and/or undertake further reading.
Important factors for macro site selection
Many factors can have an impact on the way the water is stored in the soil and on the way crops use that
water. They affect transpiration and evaporation rates and have a direct impact on irrigation scheduling. In
macro zone selection, it is important to consider the way the following factors influence water use in a
particular area or zone:
•
Climate
•
Soils
•
Crop
•
Cultural management
•
Irrigation system
•
Water quality