In the last regional update by Todd Lowe, some of the impacts of limited rainfall during the previous several months were discussed. However, subsequently, tropical waves have begun to move northward, and now typical afternoon thunderstorms have been boiling up around the state. These thunderstorms are definitely welcome and have brought much needed relief to many golf courses where pronounced year-to-date rainfall deficits were experienced. In spite of more frequent and, at times, very heavy rainfall, lake and groundwater levels are still low in many areas and more time will be required to fully recover. Even the most sophisticated state-of-the-art irrigation system is, at best, a supplement and not a replacement for rainfall. Thus, astute irrigation management still needs to be practiced to maintain consistent, healthy turf growth and appropriate course conditioning.
The ultradwarf bermudagrasses (Champion, Mini-Verde and TifEagle) have now been in use in Florida for eight to ten years, and, as to be expected, fine tuning of best management programs and practices continues to occur. This is especially the case with irrigation management. Earlier in the year and before the onset of constant high temperatures and humidity, good results were enjoyed at many courses with a basic irrigation regime of heavy applications conducted on a five to seven day interval. With this regime, and allowing the rootzone to dry down, it was possible to produce and maintain increased root system development. Heavier, infrequent irrigation cycles has long been considered the best regime for promoting maximum root system development, but it is also very important to not allow the top 1 to 2 inches of the rootzone to completely dry out. Thus an early morning shot of water or hand watering to prevent the onset of drought stress is still needed in-between the heavier applications.
With the Florida summer rainy season, management of supplemental irrigation of putting greens can become more of a challenge. This is just the opposite of what is generally assumed by most golfers. With the occurrence of frequent and, at times, heavy rainfall, it is difficult to effectively manage rootzone moisture and oxygen content. When the upper 1 to 2 inches of the rootzone stays saturated for extended periods of time, necessary soil oxygen content is displaced and the root system of the turf begins to suffocate and die. Reduced root system development is very common beginning in June and continuing until October or even November. With the development of this situation, general stress tolerance of the turf is reduced and drought stress in particular can develop very quickly. This is why it is not possible to discontinue irrigation of putting greens for more than a day or two following several days of rainfall.
While the ultradwarf bermudagrasses are a warm season turf species, deterioration in turf health and quality due to heat stress can be experienced. Problems tend to be exacerbated the first one to two weeks following routine core aeration operations when very rapid drying of the rootzone occurs around the aeration holes. Thus, similar to northern bentgrass based putting greens, ultradwarf bermudagrass putting surfaces need to be closely monitored for signs of heat and drought stress, and syringing or hand watering of hot spots.
The ultradwarfs have raised the bar as far as putting green quality and conditioning. Quality comparable to northern bentgrass based putting greens is routinely provided at Florida courses and across the Southeast. Yet, along with this has come the necessity to adopt many of the same management practices, and in particular, irrigation management during periods of intense environmental stress.
Source: John Foy, jfoy@usga.org
