Spring Greenup of dormant bermudagrass would be desirable from a use and/or aesthetic standpoint if low cost amendments could be incorporated into early season management. Four fertilizers, activated charcoal and lawn paint were applied 1 March, 2001 to a fully dormant Tifway (419) bermudagrass turf. Activated charcoal and lawn paint treatments increased turf growth, visual quality and early season turf color compared to fertilizer treatments. All fertilizer treatments generally produced greater growth than the non-treated control, while Dune liquid fertilizer produced significantly greater clippings than the other fertilizer sources tested. Visual quality was enhanced 27 days after treatment by charcoal and paint treatments. Increased canopy and soil temperatures realized from the physical amendments (charcoal or paint) were enough to induce enhanced growth, turf quality and color over chemical (fertilizer) applications.
Abstract A field study assessed the accuracy and consistency of crop water stress index (CWSI) estimates determined by two empirical models and one theoretical model for evaluation of bermudagrass [ Cynodon dactylon (L.) Pers. cv. Midiron] water status. The simplest empirical model, describing canopy temperature minus air temperature ( T c — T a ) of well‐watered turf as a linear function of air vapor pressure deficit, was inadequate for estimating CWSI, since seasonal averages of CWSI for well‐watered, moderately stressed, and stressed turf had corresponding coefficients of variation of 1170, 160, and 86, respectively. The CWSI values were also highly influenced by net radiation, as indicated by coefficients of determination for regressions of calculated CWSI on net radiation of 0.68, 0.76, and 0.33 for the three levels of irrigation treatments, respectively. The second empirical model included net radiation in the regression analysis of of T c — T a . The inclusion of net radiation in the equation for the unstressed baseline increased the coefficient of determination from 0.76 to 0.90 as compared with Model 1. The coefficient of determination for the upper baseline (which included net radiation) was 0.872, indicating a strong dependency of CWSI on net radiation. The theoretical CWSI model yielded the most accurate estimates of turfgrass water stress, as indicated by coefficients of variation for seasonal averages of CWSI for well‐watered, moderately stressed, and stressed turf of 76, 3, and 86, respectively. Midday estimates of CWSI were related to percent available extractable water, with coefficients of determination for a regression of midday CWSI on percent available extractable water of 0.988, 0.989, and 0.991 for the empirical, modified empirical, and theoretical models, respectively. The theoretical CWSI appears to be the most promising approach for a turfgrass crop water stress index for irrigation scheduling.
Almost all sports and golf facilities in the southwestern desert areas overseed bermudagrass in the late summer/early fall in order to provide a green year round season play surface. This is necessary since bermudagrass growth and winter dormancy can severely limit performance of sports fields and golf course turfs for six months or longer, which often occurs in high use periods. In the last fifteen years, the natural conversion of ryegrass back to bermudagrass has become problematic due to any single or combination of the following: (1) widespread use of ryegrass cultivars which now tolerate high temperature stress, close mowing and produce high tiller densities, (2) clientele demand for high quality turf on a year round basis, and (3) inadequate response of newer ryegrasses to standard typical cultural management practices for transition. These issues often create a condition whereby transition from the overseed to bermudagrass produces an unacceptable turf surface. A number of scenarios arise where any of the following is possible: (1) ryegrass persists for an unacceptable length of time, (2) bermudagrass is weak and thin, or (3) ryegrass persists and then fails abruptly leaving a dead straw turf mat, often without bermudagrass regrowth.
Creeping bentgrass is seasonally stressed from high summer temperatures and high humidity conditions in the desert southwest from June to mid-September. Golf greens typically show decreased stand density and poor performance by the end of this time. A preventative fungicide application program was evaluated for the prevention of summer stress typical under summer conditions. Four tank mixes composed of Alliete Signature mixed with either Chipco 26019, EXP10790A, EXP10702B, or Daconil Ultrex fungicides were applied every fourteen days from June 10 to September 17, 1997, on a >Penncross= creeping bentgrass green maintained at 5/32. The Daconil Ultrex tank mix caused some initial injury and in general, the lightest turfgrass color and the lowest turfgrass quality. EXP10702B treated turf produced, on average, the darkest turf with the leading rank score for quality. The Chipco 26019 tank mix produced the largest seasonal clipping totals, which was greater than the check. No diseases occurred on treated or untreated turf. Root dry weights in mid-October varied as much as 40% among treatments, but was not statistically significant.
Several items need consideration when products are evaluated for use as transition agents. These are (1) efficacy of ryegrass removal [rate of ryegrass decline and appearance of turf during transition], (2) tolerance and performance of incoming bermudagrass and (3) application safety for next season’s repeat overseed operations. This test was designed to evaluate application safety for the next overseeding which occurs in the early fall. Therefore, AEF was applied in the summer to bermudagrass turf prior to overseed operations. Most responses of the perennial ryegrass (overseed) turf to previous treatments of AEF 130360 occurred immediately after overseeding, from mid-October to early November. AEF 130360 applied 2 weeks before overseeding caused a significant decrease in seedling vigor, percent plot ryegrass cover, and percent bermudagrass plot straw present. Both AEF treatments applied closest to overseeding (2 weeks prior) had the least amount of initial ryegrass, the greatest amount of green bermudagrass, and later in the season, the most amount of straw (dormant) bermudagrass. Differences in turfgrass quality were not significant due to treatments at any time throughout the test, and most treatments ranked higher than the control in overall quality. Under the conditions of this test, application of AEF 130360 at either 0.64 or 1.28 ounces/product/M made one month before actual oversseding did not cause detrimental effects to ryegrass emergence, ryegrass cover, turfgrass color or overall quality.
Dimension herbicide (dithiopyr) was applied to common bermudagrass turf at 90, 60, and 45 days before fall overseeding to measure the efficacy for turf safety and for control of fall germinating POA Annua (PA). Applications were made at 0.25, 0.375, and 0.50 lbs. AI/A on each date. One half of each plot was overseeded, while the other half was not. Percent plot (PA) infestation and percent weed control was more greatly affected by the process of overseeding, than that of the herbicide applications alone. When not overseeded, the bermudagrass turf had a maximum of 45% PA control in November, which decreased dramatically to little or no control from January to March 2000. With the inclusion of ryegrass overseed, the high rate (0.50 lbs. AI/A) applied closest to the overseeding (45 DBOS) provided between 79-82% PA control over the length of the test. Actual infestation levels among non-chemical receiving control plots showed a 3X increased level in PA suppression due to overseeding, when compared to the non-overseeded, non-chemical controls. Dimension herbicide alone had little effect for PA control. When combined with overseeding, the 0.50 lb. AI/A rate, applied at 60 or 45 DBOS provided the greatest levels of PA control. The performance of Dimension on non-overseeded bermudagrass does not support the anticipated use of this chemical for PA control.
