William C. Kreuser

Evidence, Regulation, and Consequences of Nitrogen-Driven Nutrient Demand by Turfgrass

Nutrient uptake is strongly influenced by plant growth rate. Accelerated growth leads to nutrient levels incapable of sustaining the optimal growth rate, resulting in shoot to root signaling for increased nutrient absorption. The factors controlling nutrient demand in turfgrass and its consequences have not been investigated. The objectives of this research were to verify that turfgrass exhibits the principal characteristics of demand-driven nutrient uptake and to identify the primary factor controlling nutrient demand via regulation of growth rates. Kentucky bluegrass clipping production increased linearly up to annual fertilizer N rates of 600 kg ha−1 and to 1000 kg N ha−1 for creeping bentgrass. At the typical annual N fertilization rates of 150 to 300 kg ha−1 for the two grasses, N supply was the primary determinant of turfgrass growth rate, plant nutrient demand, and nutrient uptake. Nitrogen uptake accounted for over 88% of uptake of all other nutrients. Uptake of P and K were strongly related to tissue N content irrespective of soil test levels. Variations in turfgrass species and cultivar nutrient requirements and nutrient use efficiencies were found to be directly related to differences in growth rates and, by inference, to differences in nutrient demand.

Turfgrass Winterkill Observations from the Upper Great Plains: Desiccation and Cold Temperature

T HE winter of 2013–2014 was atypically harsh for many plants across the Great Plains region of the United States. Above average winds, large temperature swings, and minimal precipitation resulted in desiccation injury on many plants including many turfgrass stands. Lack of snow cover resulted in severe winterkill. Damage occurred throughout much of the state of Nebraska and southern South Dakota. Cool-season grasses such as creeping bentgrass (Agrostis stolonifera L.) and roughstalk bluegrass (Poa trivialis L.) were severely impacted despite being considered two of the most cold tolerant turfgrass species (Beard, 1973). Turf on golf course tees, fairways, and putting greens was especially susceptible to injury. Precipitation from 1 Dec. 2013 to 31 Mar. 2014 was below the 30-year average for most of central and eastern Nebraska, southern South Dakota, and western Iowa. here were only six precipitation events greater than 0.05 inches and one occasion with more than 0.25 inches of precipitation at the Lincoln Airport in Lincoln, NE (Fig. 1). Total precipitation at that location was 1.21 inches compared to average precipitation of 2.50 inches during that same period. Wind speeds were also above average during that time period with 14 days of peak wind gusts greater than 40 miles per hour (MPH) and 7 days with peak wind gusts exceeding 50 MPH (Fig. 1). Air temperatures luctuated greatly during that winter. It was common for daily maximum air temperatures to be near 50 and 60°F before air temperatures declined sharply within 24 to 48 h (Fig. 1). January 2014 was particularly severe with less than 0.20 inches of precipitation, generally clear skies, strong winds, and air temperatures ranging from -8 to 66°F in Lincoln, NE. he excessively dry conditions caused large cracks to form in ine textured soils. Cracks were visible in some USGA sand-based putting greens, likely caused by contraction of the surrounding soil. Perennial ryegrass (Lolium perenne L.) and annual bluegrass (Poa annua L.) are known to be intolerant of cold temperatures and were killed during the winter of 2013–2014. Winterkill of perennial ryegrass and annual bluegrass was Published in Applied Turfgrass Science DOI 10.2134/ATS-2014-0053-BR

Civitas Increases Clipping Yield on a Cool-Season Putting Green

C IVITAS (Suncor Energy, Calgary, AB, Canada) is an isoparain horticultural oil marketed to enhance plant defense and is certiied by the Organic Materials Review Institute (www.omri.org). It triggers induced systemic resistance to diseases leading to reduced pesticide requirements for turfgrass (Cortes-Barco et al., 2010). To mask phytotoxicity, Civitas is mixed with a copper phlalocyanate-based pigment called Harmonizer (Suncor Energy, Calgary, AB, Canada). Civitas and Harmonizer can be mixed on site (called the Two-Pack) or premixed at the factory (called Civitas One). here are anecdotal reports of increased clipping yield and reduced ball roll distance following application of the Two-Pack to putting greens of cool-season grasses, but these claims have not been substantiated scientiically. Increased clipping yield or reduced ball roll distance may limit the use of Civitas. Our objective was to determine the efect of Civitas, Harmonizer, and their combination on the clipping yield of cool-season grasses maintained as a putting green. his study was conducted in 2011 and 2012 on a mature stand of 60% creeping bentgrass (Agrostis stolonifera Hud. ‘Penncross’) and 40% perennial biotype annual bluegrass (Poa annua var. reptans) putting green at the Cornell University Bluegrass Lane Turf and Landscape Research Center in Ithaca, NY. he green was constructed approximately 15 years ago from the on-site Arkport ine sandy loam soil with a 3-inch layer of sand from monthly topdressing applications. Plots were mowed daily at 0.12 inches with a Toro Greensmaster 1000 (Toro Co., Bloomington, MN), fertilized weekly from May until October with urea at 0.1 lbs N/1000 t, and irrigated to prevent drought stress. he experiment was a randomized complete block design with four replicates of 8 by 4 t plots. Treatments included an untreated control, the high labeled rate of Civitas oil applied alone (16 l oz/1000t), Harmonizer pigment alone (1 l oz/1000t), and Civitas and Harmonizer mixed on-site (TwoPack; 16 and 1 l oz/1000t, respectively) and Civitas One Published in Applied Turfgrass Science DOI 10.2134/ATS-2014-0012-BR