Trinexapac-ethyl and nitrogen rates to increase turf coverage of Kentucky bluegrass during summer season
2024
Lee, S.K.
The summer decline is a symptom that causes turf to deteriorate in hot and dry weather. During summer, cool-season turfgrasses are subjected to drought and heat stress leading to severe decline in turf quality. Plant growth regulators (PGRs) are organic compounds synthesized within plants or applied as substance which can either increase or decrease turf growth. One of the most widely used PGRs is trinexapac-ethyl (TE) which plays a role in cell elongation and inhibiting gibberellic acid synthesis. TE has been widely used in turfgrass management to reduce clipping, increase tolerance to physiological stress, and improve turf quality. The objective of this study is to evaluate the effects of TE and nitrogen (N) rates to increase turf coverage of Kentucky bluegrass during summer. Three TE levels were 0.08, 0.16, 0.32 ml m⁻² as low, medium, and high levels, respectively. Five nitrogen (N) rates were 0, 3, 6, 9, and 12 g N m⁻², respectively. At high temperatures, the low TE level and 6 g N m⁻² treatment produced the greatest turf coverage. As TE level increase, negative effects were produced on turf coverage. When the air temperature range was appropriate for cool-season grasses, the low TE level and 9 g N m⁻² treatment resulted in the greatest turf coverage. The application of PGRs and N rates can minimize and recover the injuries from summer decline. However, attention should be taken to apply high PGR level and high N rates when the air temperature is above the optimum temperature for Kentucky bluegrass.
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