Soil Moisture Management on Greens

When I visit golf courses around the world, moisture issues are the number one problem of greens management I see. Overwatering to the point of creating an area that is unsuited for plants to survive is common. Implementing a daily watering protocol can save the golf course so much stress and even a Superintendent’s job.

Whether your course is getting average rainfall or having to supplement the rainfall with irrigation, applying the correct amount of irrigation is one of the most challenging jobs a superintendent has to face.

Do you know the proper moisture reading for your greens? You would be surprised that most turf managers do not.

Turfgrass will grow more roots where moisture and soil conditions are correctly available and when plants are photosynthetically active to generate carbohydrates for storage. If the moisture needed for the plant sits near the surface, the plant’s roots will not go searching deeper for more. Equally, roots will not burrow through dry soils to search for moisture; they will grow deeper if the lower ranges of the root zone hold more moisture than the high ranges. So watering deeper on certain nights or a penetrating surfactant can play a significant factor here.

As the summer heat takes its toll, in dry and unsuitable conditions, some turf can see its root mass seriously depleted – and with it, the ability to utilize soil moisture deeper in the profile. Trials typically show a 20 to 40% reduction in root mass under drought stress but can be as much as 60%.

Overwatering occurs for many reasons, but one of the biggest is the fear of getting too dry, and the tendency is to overwater and keep it too wet.

A great water source and well-drained soils can usually tolerate this more than a course with poor water quality (I.E., effluent or grey water) high in salts can lock up the soil. The downside is that nothing good comes from overwatering golf courses, especially the putting surfaces.

Unless you have the latest and greatest irrigation system that will read rainfall, measure E.T., or have moisture meters in the greens, you must implement a proper moisture management protocol yourself.

A proper water management protocol is not tricky, and you do not need a degree from MIT. The aim is to balance the soil’s water holding capacity and sufficient oxygen for healthy growth. However, that can be compromised by hydrophobic soil particles, which have lost the ability to hold onto the water. That can happen on a microscopic level, with individual particles, or on a grander scale up to a widespread hydrophobic dry patch.

Additionally, it enables the way that water is applied with irrigation to be more efficient. Irrigation little and often, which keeps the surface and top layer moist, could encourage shallow roots in that zone, with less of the beneficial deeper rooting retained. Water near the surface is also more prone to evapotranspiration in the heat, but its nature leads to more changeable playing surface characteristics throughout the day.

Soil moisture can be better retained deeper in the profile by irrigating less often but applying more water at each application. This encourages deeper root retention and enables better utilization of moisture and nutrients, along with consistent surface playability, providing the water has the means to infiltrate the surface quickly.

Saturated soils are lower in oxygen, which is detrimental to developing healthy turfgrass roots and turf grass vigor.

Additionally, saturated soils have a more significant temperature increase under high air temperatures than properly irrigated soils under the same temperatures. From a turf health and management perspective, there is no advantage to having soil moisture levels higher than necessary at any time. In some instances, higher moisture levels are detrimental to turf’s health.

Overwatering also may increase mowing frequency to keep up with increased clipping yield compared to maintaining dryer conditions. As this occurs, you are also flushing out necessary nutrients because they have been leached thru the soil profile, causing an increase in fertility costs.

One of the most significant hidden impacts of overwatering is its effects on playability. Overwatering creates soft playing conditions that most golfers hate.

What is the cost of overwatering your golf course? The cost of overwatering depends on many factors, including turfgrass species, the region of the country you are in, the age of the green, and the cost of purchasing water.

Some of the costs include:

  • Increased use of fungicides to combat disease and algae
  • Labor to do repairs to wet areas from ruts caused by maintenance equipment
  • Extra time and effort to vent or spike the overwatered surface and get oxygen around the root
  • Cost of the irrigation water, if applicable, and the utilities to run the pump station
  • Slowdown of play because of less ball roll and shorter drives
  • Golfer dissatisfaction and the resulting loss of play
  • This can also lead to the reconstruction of the green itself as it starts to break down.

What can you do?

  • Use a moisture meter and soil probe to determine if the turf needs water and only water to the depth of the root zone and to the areas that need it.
  • Keep the course on the drier side, and when you get natural rainfall, the course will be more receptive. Also, using surfactants to manage the water through the profile is very important. Research and find the best product for you.
  • Walk the greens daily, buy a good moisture meter, and only use the irrigation system properly when needed.
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The GrassCast Podcast Episode 7

Agronomist and Golf Course Consultant Lewis Sharp from Tee-2-Green along with Jim Holden from Turf Care, discuss Interseeding and Tee-2-Green products with Colm McCarthy on The GRASSCAST podcast (March 4, 2021).