Pulse Irrigation

Salt affected turfgrass sites present irrigation challenges. During droughty periods or restricted water use, salts can accumulate in the rootzone impacting turfgrass growth by moving into the rootzone through the processes of evapotranspiration and capillary rise. Capillary rise occurs when irrigation or rainfall is insufficient during both the growing season or when turfgrass growth is slow (winter). Thus, controlling salts requires a year round program.

Surface and subsurface cultivation is essential to effective salt leaching. When sodic (sodium) conditions are present a good rule of thumb is that the effects from cultivation last ½ the time as on non-sodic soils.

Irrigation practices need to focus on keeping total soluble salts (TSS) moving downward. For this reason light frequent irrigation is not recommended because surface salt buildup is rapid, capillary action can cause salts to rise from the subsurface into the rootzone, and cool season grasses are very susceptible to salt injury in the summer. If light frequent irrigation is needed due to shallow root system, frequent leaching will be required. In the case of USGA constructed greens or athletic fields flushing the perched water table may be needed.

Continuous slow irrigation through cycles (pulse irrigation) is better than ponding or periodic heavy leaching to remove TSS from the rootzone. Pulse irrigation as a general rule means applying 0.5 to 1 cm of water per application with an interval of 2 to 4 hours for loams and 3 to 6 for clays. The principle behind pulse irrigation is to have water flow through the soil as unsaturated flow, which moves in a more uniform downward motion and occurs through the micropores. Ponding or heavy continuous watering is saturated flow, which occurs mainly through larger macropores resulting in inadequate leaching of the micropores.

When initiating a pulse irrigation program try to time with a rain event, and instigate traffic restrictions to the turf to minimize compaction and wear injury. Routine continuous leaching to keep TSS in the acceptable range should be the goal.


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