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Soil, the Natural Irrigation System

Most, if not all, landscaping plants in arid environments require supplemental water to survive and thrive. So, making sure that drip emitters or bubblers are properly located near plants and that the irrigation system functions properly are essential tasks for landscape managers.

But there’s more to it than that.

Delivering water to the area where plants are located is only part of the job. A complete and properly functioning irrigation program must ensure that the water actually arrives at the root zone and is available for uptake by the plant’s roots. This is not as simple as we might think.

Soil is nature’s own unique irrigation system designed to deliver water from the soil surface to the root zone. It does so via large and small pore spaces that, connected together, form networks of tiny “pipes” through the soil matrix.

At least that’s how it’s supposed to work. There are certain factors that determine whether the soil can fulfill its role as a natural irrigation system. Primary among these are soil type and compaction.

Soil type refers to the sizes of the solid particles that make up the soil: sand, silt, and clay. The larger the particle sizes, the larger the spaces –pores—between them. The smaller the particles, the smaller the pore spaces between them.

Compaction is a soil physical condition found in almost all residential, commercial, and municipal properties. Surface traffic of all kinds (construction equipment, vehicles, maintenance equipment, and pedestrian foot traffic) crush the soil particles together, squeezing the spaces between them until the tiny “pipes” collapse and become blocked. When this happens, water dripped onto the soil’s surface infiltrates very slowly or not at all, resulting in ponding, evaporation, or erosion. In some cases, the water we drip on the soil never reaches the roots in sufficient amounts, resulting in wasted water and struggling plants.

Landscape managers responsible for ensuring the effectiveness of irrigation programs must keep in mind that the soil is the second half of every irrigation system. Knowing the soil type and its compacted condition, and hence its capacity to distribute water to the root zone, is vital in order to properly manage this interconnected system.

Article provided by Roger Hartzog of Tree Theory