Saline Irrigation Water in Urban Areas Poses Problems for Vegetation Management

By Marco Neftali Minor*

Explorations: The Texas A&M Undergraduate Journal

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Soil salinization is often associated with water scarcity, an increasing problem affecting people around the world. Unpredictable rainfall and increasing urbanization are predicted to impact our state simultaneously. Sodium concentration in aquifer water is also expected to increase with the need to explore deeper water sources in the future. The application of highly saline water to any soil degrades its quality. Reversing the effects of high sodium irrigation water requires the application of clean water that washes the sodium from the soil. The adoption of alternative irrigation techniques to reduce soil sodium content at a large scale could assist in maintaining urban ecosystems and help urban trees in Texas.

An investigation of irrigation water chemistry and its effects on urban soil was performed around prominent live oak trees and trees around campus. Soil pH and electrical conductivity were compared between July 2013 and February 2014. Results indicated high levels of sodium in the soil and high soil pH during summer months. It was concluded that these levels were due to extensive irrigation in drought conditions of 2013. Electrical conductivity and pH fell with increasing distance from sprinkler heads during winter months with more typical rainfall patterns.

Adoption of rainwater harvesting systems (RHS) offer an engineering solution that would mitigate the effects of long term usage of highly saline waters on irrigated soils. Using a framework as described by William Hall Saour’s Undergraduate Research Scholar Senior Scholars Thesis, RHS will reduce injury of urban trees and plants, improve the soil environment, and reduce groundwater consumption. Technical guidance, descriptions of legal compliance, and descriptions of further benefits for RHS management are readily provided by the EPA.

How do we prevent sodium build up in soils when watering is necessary during drought and periods of high temperatures? One possible solution is to minimize the amount of saline irrigation water that is directed towards the base of trees. Irrigation methods that are designed for maintenance of turfgrass are nearly always excessive relative to the amount needed to support nearby trees. Adjusting irrigation heads so that water is directed away from tree trunks is a simple method of reducing salt buildup in a rooting zone.

By increasing the cooling effectiveness of shade trees by improving crown quality, tree-care and tree-replacement costs are reduced. Irrigation with sodium laden ground water is causing urban soils to accumulate sodium and become increasingly unsuitable for vegetation. It is critical that Texans adapt and apply creative water usage techniques for conservation purposes.

 *Marco Neftali Minor earned a Baccalaureate Degree in Ecological Restoration from the Department of Ecosystem Science and Management, spring of 2014. He conducted this research in collaboration with Eboni Hall, graduate student in ESSM, and Dr. Jason G. Vogel. Drs. Jacqui Aitkenhead-Peterson (Crop and Soil Sciences) provided soil analyses.  

 More info:     Contact Marco Minor