The primary problem created by hydrophobic soils in gardens is reduced water/nutrient uptake and vigor in plants. So what can gardeners do to mitigate the condition? First, plants that are associated with higher water repellency can be avoided or removed. These include specimens that contain waxes, resins or aromatic oils high in lipids, such as eucalyptus or conifers. Second, coarse textured soils have demonstrated a greater affinity for water repellency than fine textured. Soils with a considerable content of clay and loam provide a more balanced advantage. Third, good watering methods and application of mulch can help prevent a complete drying of soil.
On a broader scale, hydrophobic soils can create huge problems. Chemical runoff, flooding and erosion can occur in agricultural settings, forests, and additional plant communities. Many publications have been written about the correlation of higher hydrophobicity in areas following fire events, making landscapes particularly prone to flooding and erosion. Changes in drought, fire and rainstorm frequency and intensity make study of hydrophobic soils a priority in order to mitigate environmental damage.
According to an article published in Planet Earth in 2007, “Evidence is mounting that soils can switch rapidly from a wettable to a hydrophobic state once their water content falls below a critical threshold”, and “that even a moderately hydrophobic soil can resist wetting for hours or even days.” It is possible to ease this condition, whether we are growing roses in the backyard or soybeans in the field, with proper horticultural methods.
Many professional and home gardeners have likely encountered an annoying development during the dry, hot periods of summer. While sensibly giving our gardens a thorough watering, we occasionally see water pooling on the soil’s surface, running off in rivulets, and/or failing to penetrate into the root zones of our treasured plants. It seems counterintuitive that when our soils are driest, they resist absorption of water. This condition is called hydrophobicity.
Soil particles are often coated with naturally occurring, water repellent, organic compounds that contain lipids. These compounds can be derived from decaying plant matter, fungi, and microorganisms. During cooler, wetter times of the year, there seems to be an understanding among the soil’s constituents that water will be accepted and utilized. However, when dry spells occur, the lipids may take precedence, and soils may repel water.