Use of Drip Irrigation in Orchards

Abstract

The use of drip irrigation in orchards is increasing worldwide. Water shortage, prevention of ground water contamination, and improved production are the main reasons for this increase. The combination of partial wetting of the soil and control of the water penetration depth considerably increases the efficiency of irrigation. Recent technological improvements permit maintenance of a constant volume of irrigated soil in which gradients of soil water matric potentials and mineral concentrations exist from the irrigation point to the margins of the wetted zone. Because water and mineral uptake is a function of soil matric potential and mineral concentration, respectively, optimal uptake rates by certain portions of the root system always exist along these gradients for any given environmental conditions. Gradients of air concentration act similarly and permit maintenance of high water availability without any interference with root aeration. Due to the relative ability of the roots to exchange water, minerals, and, possibly, oxygen, the entire root system functions more efficiently compared to root systems under conventional irrigation methods. Physiological root restriction effects induce the formation of a large number of small roots with frequent branching. Consequently, the relative surface area for water and mineral absorption is increased several-fold, and the increased number of root tips that are known to be involved in production of hormones (such as gibberelins and cytokinins) is significant. Evidence for enhanced fruit bud formation under conditions of root restriction is presented here. Water treatment and filtration technology has improved, and clogging of surface or buried drip systems now can be minimized, which also increases the suitable range of water quality for use in drip systems.