WATER REQUIREMENTS TRIALS
Ian Smith HortiCulture
Introduction
Most major Australian cities have experienced drought for many years, water reserves are low and
consequently restrictions have been applied to garden and landscape irrigation. Though reference
evapotranspiration is available from the Australian Bureau of Meteorology, it has not been routinely applied to
water scheduling for garden and landscape plantings. Irrigation scheduling based on evapotranspiration, soil
moisture levels etc. has been applied to crops, but very little data is available on the response of ornamental
species to reduced irrigation levels. Landscape plants are valued for their appearance and the concept of
yield is not relevant. It has been reported that some species utilized for landscapes have the ability to
maintain acceptable aesthetic quality under reduced irrigation (Pittenger, et al.
2001). Landscapes are also difficult to characterize because they often consist of small plantings of
numerous species.
Objective
The primary objective of this project was to determine the response of 37 ornamental species to irrigation
treatments based on evapotranspiration and to define estimates of ornamental plant water needs for
acceptable aesthetic appearance.
Based on performance in relation to applied irrigation, develop a classification system for the selected plants
indicating their ability to tolerate dry conditions with low irrigation input. Use this classification system as a
basis for the promotion and sale of ornamental plants with reference to their water requirements during
on-going drought and water restrictions in many areas of Australia.
Null hypothesis
All plants will respond identically to various levels of irrigation based on a percentage of full replacement of
evapotranspiration losses.
Evaluation of the performance of landscape ornamental plants in response to
irrigation treatments based on evapotranspiration
Abstract
The objectives was to determine the
response of 37 ornamental plants to
irrigation treatments with respect to
evapotranspiration and to define estimates of
ornamental plant water needs for acceptable
aesthetic appearance.
Experimental plots were established at
Silvan, Victoria, Australia, consisting of five
100 m2 blocks allowing four irrigation
treatments replicated five times. Single
plants of each of 37 species were planted
into 20 m2 experimental units within the
drip-irrigated blocks.
Irrigation treatments were initiated in
November 2005 and consisted of 1.0, 0.75,
0.50, 0.25 evapotranspiration.
Irrigation scheduling was determined by a
Weathertrak Pro controller utilising
evapotranspiration generated from Bureau
of Meteorology weather data calculated by
the Penmen-Monteith formula and forwarded
daily to the controller through a GPRS
modem connection.
