1998 Iowa Turfgrass Research Report

1998 Iowa Turfgrass Research Report

Effect of Primo on the Establishment of Kentucky Bluegrass in a Mature Grass Stand

Barbara R. Bingaman, Nick E. Christians, and Michael B. Faust

The objective of this study was to determine if application of the growth regulator, Trinexapac-ethyl (Primo), would enhance the incorporation of new cultivars into existing stands of turf. This study was conducted at the Iowa State University Horticulture Research Station. The study was in an established area of 'Park' Kentucky bluegrass that was not fertilized in 1997. The soil in this plot was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.2%, a pH of 7.8, 3 ppm P, and 75 ppm K. It was overseeded with 'Baron' Kentucky bluegrass, a cultivar that has dark green seedlings. The color difference between 'Baron' and 'Park' should enable percentage cover estimations to be made for each cultivar..

Individual plot size was 5 x 5 ft with three replications and 3 ft barrier rows between replications. There were four treatments including an untreated and unseeded control and an untreated and seeded control. Primo was applied at 0.5 fl oz/1000 ft² to overseeded and unseeded plots. Primo applications were made two weeks before overseeding (Table 1). The Primo was mixed with 283 ml of water per plot and was applied at 30 psi using a CO₂ backpack sprayer equipped with TeeJet™ #8006 flat fan nozzles. This rate translates to 3 gal/1000 ft².

Rainfall was quite sporadic following overseeding. Irrigation was used to keep the bluegrass in good growing condition and to enhance germination.

Visual turf quality data were taken weekly beginning on August 21 when the Primo was applied. Data were taken on September 5, September 12, September 18, September 26, October 2, October 9, and October 14 (Table 1). Visual quality was assessed using a 9 to 1 scale: 9 = best, 6 = lowest acceptable, and 1 = worst quality.

Overseeding was performed on September 12. At the time of overseeding, the entire plot was sliced with a vertical mower in three directions. The plot was raked to remove thatch and debris. 'Baron' Kentucky bluegrass was seeded by hand into individual plots at 1.5 lb/1000 ft² and raked into the slits.

On September 12, the plots treated with Primo had less growth and were not as green when compared with the untreated plots. By September 18, the quality differences were gone and there were no further quality differences through October 14 (Table 1).

The plots were monitored weekly for germination after September 12. Seedlings were first observed on September 26 in the overseeded plots. The seedlings were still too small to take % cover data by October 14. On October 9 and October 14, we confirmed that there were young seedlings in both the Primo treated and untreated, overseeded plots. The seedlings were so small that estimations of populations could not be made at this time. The plot was monitored weekly through November 12. At this time, the temperatures were prohibitive for further seedling growth so we ceased monitoring the plot. Percent cover data will be taken for both cultivars in the early spring. The color differences between the 'Baron' and 'Park' should be quite visible at spring greenup.

Table 1. Visual quality of 'Park' Kentucky bluegrass.

	Materials	Rate (fl oz product/1000 ft2)	Overseeded	Sept 5	Sept 12	Sept 18	Sept 26	Oct 2	Oct 9	Oct 14
1	Untreated control	NA	no	6	6	6	6	6	6	6
2	Primo	0.5	no	6	6	6	6	6	6	6
3	Primo	0.5	yes	6	5	6	6	6	6	6
4	Seeded control	NA	yes	6	5	6	6	6	6	6
	LSD0.05			NS	NS	NS	NS	NS	NS	NS

Primo treatments were made on August 21 and the plots were overseeded on September 12, 1997.

NS = means are not significantly different at the 0.05 level.

ISU Horticulture:Publications:1998 Turfgrass Report

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