HO-154
YARD AND GARDEN
HORTICULTURE DEPARTMENT COOPERATIVE EXTENSION SERVICE WEST LAFAYETTE, INDIANA 47907
DESIGNING TRICKLE
IRRIGATION SYSTEMS
by Lawrence D. Cammarata, graduate in landscape management, and David F. Hamilton, assistant professor of horticulture
Introduction
Trickle, or drip irrigation, has been traced back to the early Roman aqueduct period where broken clay pipes slowly released water in plant rows. However, it was not until the founding of modern Israel that the concept of putting a small amount of water over the root zone, when needed, and at an exact rate began to be developed commercially. Early systems had many problems: plants close to the water source received too much water while plants at the end of the line wilted; the orifices clogged easily; and elevation changes further accentuated the lack of information in hydraulic engineering. Trickle systems have since proven very efficient, and the use of trickle systems has increased dramatically as nurseries have been faced with rising water costs and scarcity. Today, trickle irrigation systems are becoming an integral part of nursery operations over the world, and many growers have reported very significant increases in production with marked reductions in water and labor requirements.
The idea of trickle irrigation is to water daily but not too much —replacing only the moisture that the plant uses each day, thus preventing water stress (as opposed to correcting water stress using overhead irrigation systems). With trickle irrigation, plants are not subjected to moisture stresses which cause cessation of growth, wilting, and/or death. Given the proper combination of sunlight, air and nutrients in the soil, most plants thrive with only small amounts of water applied daily. Soil moisture can be maintained at a uniform high level throughout the growing period with trickle irrigation- Growth and production potential are greater when plants are not subjected to the wetting and drying cycles occurring with overhead irrigation systems. Compact root systems can be developed in field-grown plants by applying water so that it rewets the same soil area in successive water applications. In one experiment, about 90 percent of the root system was recovered when 4-year old shade trees, each having a 36-inch ball, were dug with 60-inch tree spade (9).
By confining the wetting area to the root zone of the plant, there is a dramatic savings in water, weed growth is reduced, and nutrients are not readily leached from the soil. Another advantage is that since the area is not saturated, the soil temperature is increased — contributing to still greater plant growth.
In this era of high interest rates, it is important for nurserymen to produce plants in the shortest possible time to maintain ample cash flow. Trees produced by trickle irrigation can be sold in 5 to 6 years at the same size as those that were produced by other methods in 7 to 10 years (9). Also, trickle irrigation rescues growers that have to operate
underwater restrictions because of limited water supplies in their areas.
Thus, the investment in trees, planting, and maintenance is discounted over a shorter period of time, which at high interest rates, is desirable. An investment in trickle irrigation could be well worth considering. For nurserymen faced with a water shortage, it is a necessity.