Dealing with Drought

What is a Drought?

There are a number of types of drought, with two of these being of particular interest to the turf manager.

1. Meteorological drought; which is a prolonged period of unusually dry weather where some rain might normally be expected. It is usually defined as more than 14 days with no significant precipitation which causes a period of moisture deficiency.

2. Agricultural drought; which is defined as a soil moisture deficit. For turfgrasses a soil moisture deficit figure of 75% might be considered as a drought situation.

Drought Resistance Mechanisms

There are a number of mechanisms by which plants survive drought conditions:

  • Dessication postponement - the ability to maintain adequate levels of water in plant tissue: There are two types - water savers (which conserve water and this would be the first phase for most turfgrasses) or water spenders (these plants consume large quantities of water, depleting the surface layers and exploring the lower layers - these types are not turfgrasses);
  • Dessication tolerance - the ability to function whilst dehydrated (this would be the second stage for most turfgrasses, although the relative amount of functioning would vary between species) and ultimately dormancy;
  • Drought escape (avoidance) - complete a short-term life cycle during the wet / moist season. A typical turfgrass would be annual meadow grass.

Symptoms of Drought

  1. The grass has a sheen to its appearance;
  2. Footprinting occurs. This is where the grass lacks turgidity and is therefore slow to stand back up after being walked on;
  3. There is a reduction in grass clippings;
  4. The turf starts to become less dense and there is a reduction in tillering,
  5. The grass leaf becomes narrower;
  6. There is noticeable drying out of high spots in turf areas, with the grass losing its greenness quickest on these areas;
  7. Root growth occurs in moist soil zones only;
  8. There is a reduction in photosynthesis
  9. The leaf stomata close as the guard cells contract, reducing transpiration;
  10. Root hairs can be damaged as roots shrink. As cells become smaller with less water content, the root hairs are pulled away from the soil particles;
  11. There is a thickening of the root surface layer (hypodermis) which reduces the uptake of water;
  12. The leaf cuticle thickens reducing transpiration even further.

Reducing the Effects of Drought

A number of practical tasks can be undertaken to assist turf in standing up to drought conditions.

  1. Keep the turf appropriately watered to maintain plant life and ability to withstand wear. Be careful not to overwater to produce a lush green sward, as this will reduce the quality of the turf and be wasteful of limited water supplies.
  2. Consider the use of computer controlled irrigation systems instead of just relying on guess work for irrigation requirements. Computer controlled systems can help to reduce the actual amount of water applied to turf by some 30% or so.
  3. Encourage the use of more drought resistant species and cultivars wherever possible.
  4. Look into the possibility of inoculating turf with arbuscular mycorrhizal fungi. Research has indicated that creeping bentgrass turf which had been inoculated with this fungi withstood drought conditions better than turf without the inoculation.
  5. Encourage the practice of irrigating to a suitable depth, for example 150mm, and allow the turf to dry before further irrigation to depth takes place. This will encourage grass roots to explore and move into the lower moist soil zones to extract the available water. Frequent shallow watering will only encourage the grass roots to primarily stay within the surface area. This will significantly reduce the drought resistance of the turf.
  6. Ensure adequate aeration takes place at appropriate times of the year. This will encourage the development of a deeper rooted turf providing it with the resources to better withstand drought conditions.
  7. Raise the height of cut slightly to reduce the level of stress caused to the plant by lower heights of cut.
  8. Reduce the frequency of cut. This will reduce the amount of water use.
  9. Ensure mower blades are sharp to prevent bruising the grass leaves. Bruising and tearing increases the water use rate of plants.
  10. Lightly top-dress the turf to protect the base of the turf from sun and wind, and to reduce the potential of the turf surface from cracking.
  11. Keep the turf to as high a height as practical throughout the whole of the year. This will encourage more root growth than would otherwise have occurred and provide for an improved chance of withstanding drought conditions.
  12. Carefully control and manage the amount of usage taking place. This may not be popular, however, it can ensure a suitable playing surface is available for a longer period of time and the turf will also be in a better position to return to a 'first-class' condition upon resumption of suitable weather.
  13. Avoid excessive amounts of nitrogen when applying a fertiliser. Excessive amounts encourage excess top-growth at the expense of root growth and this will be regretted during dry periods.
  14. Regularly spread wear throughout the year to reduce compaction problems.

 

Monitoring Moisture Conditions

A number of methods can be used to aid the turf manager in deciding when to water and how much to apply:

  1. Observe the grass plant. This is something which should be done anyway, however, take a slightly more active role during dry spells. Especially take note of the colour (and 'sheen') and leaf shape - does it try to fold in on itself (perennial ryegrass, annual meadow grass), or is it very tightly rolled (fescues)? This can be an early sign of the plant starting to wilt.
  2. Make a note of how many boxes of clippings are removed during the growing season. As the number of full boxes decrease then be aware that this might be the consequence of a reduction in the amount of water available in the soil.
  3. Extract and examine soil cores. If the soil is very dusty then little moisture is present. Also if the lower parts of a core fall apart this will also indicate poor moisture content at this depth.
  4. Use a soil tensiometer to measure how difficult it is for turf to extract water from the soil.
  5. Use a moisture meter. The accuracy of some of these can leave much to be desired.
  6. Use a gypsum block embedded within the turf area. Electrical resistance meters are then connected to these for readings to be taken. Effective use of these can help to reduce the actual amount of water applied to turf by providing accurate soil moisture measurements in contrast to theoretical estimates. A saving of greater than 50% in water use has been recorded for one golf course which used this method.
  7. Devise a soil moisture balance sheet to chart the rise and fall of available water.
  8. Install a weather station to record and monitor local weather data. This can then be used to make better informed decisions on irrigation needs.

References and Further Reading

  1. Hanson, A.A. & Juska, F.V. eds, (1968),'Turfgrass Science', American Society of Agronomy, 151-186
  2. Beard, J. (1973), 'Turfgrass Science and Culture', 261-303
  3. Russell, E.W. (1973), 'Soil Conditions and Plant Growth', 448-478
  4. Shildrick, J. (~1984), 'Turfgrass Manual', The Sports Turf Research Institute, 51
  5. Barrie, I. & Hemstock, D. (1992), 'Too Hot to handle', Greenkeeper International, January, 42-43
  6. BTLIA, (1990), 'Deciding when water is needed', Turf Management, May, 24-26
  7. BTLIA, (1990), 'Measuring Available Water Capacity', Turf Management, June, 21
  8. Beard, J. (1991), 'A Manual on Golf Course Construction, Turf Establishment and Cultural Practices', 15-18
  9. Handreck, K. & Black, N. (1991),'Growing Media for Ornamental Plants and Turf', 243-260
  10. Hacker, J. & Harbridge M. (1991), 'Turning on the taps', Greenkeeper International, April, 8-9
  11. Hacker, J. & Harbridge M. (1991), 'Drought', Greenkeeper International, June, 24-28
  12. Sainsbury, C. (1993), 'Accurate Irrigation', Greenkeeper International, August, 37-39
  13. Anon, (1996), 'Computer Irrigation. Can it pay for itself?', Turf Management, April, 30
  14. Tilly, H. (1996), 'Real World Test. Irrigation Equipment', Greenkeeper International, November, 15-20
  15. Park, C. (1997),'The Environment. Principles and Applications', 354-356
  16. Gemm, J.N. et al, (1997), ' Mycorrhizal fungi improve drought resistance in creeping bentgrass', Journal of Turfgrass Science, The Sports Turf Research Institute, 15-29
  17. Anon, (1998), 'Green grow the fairways', Turf Management, April, 29-31
  18. Taiz, L. & Zeiger, E. (2002),'Plant Physiology', 591-623