
Study: More water less often for more, deeper roots
A study by researchers at the University of Maryland has shed more light on the benefits of deep, infrequent irrigation with light, frequent watering practices in bentgrass putting greens.
According to the two-year research project, bentgrass subjected to deep and infrequent irrigation resulted in more and longer roots at a variety of soil depths than plots treated with light, frequent irrigation. The findings were consistent with previous research studies indicating that soil drying results in improved rooting in bentgrass.
When averaged over four soil depth ranges between 0 and 24 cm, plots that were treated with deep, infrequent irrigation also exhibited higher total root count, total root length and total root surface area than plots subjected to light, frequent irrigation.
The research, entitled Creeping Bentgrass Putting Green Turf Responses to Two Summer Irrigation Practices: Rooting and Soil Temperature, was conducted in 2006 and 2007 by Peter Dernoeden, Ph.D., and Jinmin Fu on a USGA-spec green at the University of Maryland Turfgrass Research Facility in College Park, Md. The objective of the study was to evaluate the affects of light, frequent irrigation and deep, infrequent irrigation on rooting of bentgrass on a sand-based rootzone.
The researchers’ findings were published in the May-June edition of Crop Science.
The research green, seeded with Providence creeping bentgrass in 2005, was subjected to two irrigation regimes throughout both years of the study. Light, frequent irrigation included daily watering to replace moisture lost to evapotranspiration. Deep, infrequent irrigation was applied at the first sign of leaf wilt, which ranged between three and seven days. A total of 50 liters of water was applied during each application to each plot, measuring 1.8 meters by 2.4 meters.
Data was collected detailing average root diameter, total root count, total root length and total root surface area over intervals of 6 cm soil depths as well as the entire 0 cm to 24 cm profile depth. Measurements were recorded over three dates from May through September in 2006 and June through September in year two.
Soil moisture was an average of 9 percent higher in the light, frequent plots in both years of the study in the top 6 cm of the profile and 6 percent higher in the top 15 cm.
Total root count was higher in the deep, infrequent program when averaged over the 0 cm to 24 cm rootzone in both years of the study. Total root length also was greater in plots subjected to deep, infrequent irrigation in both years of the study when data was averaged over the entire 0 cm to 24 cm profile. Likewise, a similar relationship was detected when averaging data for total root surface area. Root diameter, however, was smaller in plots subjected to deep, infrequent irrigation.
Total root count, total root length, total root surface area and root diameter were, when averaged over the entire 0 cm to 24 cm profile, were greater in the first year of the study, a phenomenon the researchers said might be attributable to higher levels of nitrogen in 2006 and increased levels of organic matter.
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