Irrigation Water Influenced by Soil Texture

Irrigation water quality is always a concern during the summer. Suitability of irrigation water is determined by the electrical conductivity
of the irrigation water (EC_i) and the level of sodium (Na⁺), magnesium (Mg⁺²), and calcium (Ca⁺²) ions.

Electrical conductivity is measured in decisiemens/ m (dS/m). In some instances the value maybe reported in microsiemens/cm (dS/m). The EC threshold for turfgrasses is higher on well drained sandy soils versus a clay soil. For example the threshold for couchgrass (Cynodon dactylon) is two and half times higher on sand than on clay.

Wilt Symptoms Can Be Caused by Several Factors

As summer progresses turf wilt symptoms become quite apparent. There are a couple of causes of "wilt symptoms" besides lack of rainfall or irrigation water.

Localised dry spots (LDS) are a serious problem on sand-based creeping bentgrass or couchgrass putting greens or athletic fields throughout South Africa and Australia. Symptoms appear as circular areas varying from 100 cm to several meters in diameter that progress from a bluish wilt to a whitish brown color. In some instances, symptoms appear more serpentine.

The cause of LDS is due to a hydrophobic soil condition that occurs in the upper 5 cm of the soil profile. Sand particles are partially coated with an organic material that repels water resulting in the wilt/drought like symptoms. The source of the organic material may be a result of soil fungi. Fairy ring is often, but not always associated with LDS.

To determine if LDS is present take a soil core from the suspected site and add water droplets along the soil profile. If the droplet beads and fails to penetrate LDS is present. Usually the water will bead in the upper 2 to 4 cm of the soil profile. Wetting agents are effective in many situations and should be used if LSD is a problem. Reducing the amount of thatch accumulation, and coring on a regular basis may help reduce LSD severity. In some instances where fairy ring is the cause, drenching an appropriate fungicide after coring may help alleviate symptoms.

To determine if LDS is present take a soil core from the suspected site and add water droplets along the soil profile. If the droplet beads and fails to penetrate LDS is present. Usually the water will bead in the upper 2 to 4 cm of the soil profile. Wetting agents are effective in many situations and should be used if LSD is a problem. Reducing the amount of thatch accumulation, and coring on a regular basis may help reduce LSD severity. In some instances where fairy ring is the cause, drenching an appropriate fungicide after coring may help alleviate symptoms. If LDS is not the problem, check for grub damage. A common misdiagnosis for these "wilt symptoms" is the irrigation heads are not working properly. Take a minute to peel pack the turf to check for grub damage.

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