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Neil L. Heckman, Roch E. Gaussoin and Garald L. Horst

Sod heating during storage can limit the distance sod may be shipped. Two experiments were conducted to determine the effect of multiple preharvest applications of trinexapac-ethyl [4-cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid methyl ester] at 0.23 kg·ha-1 (0.21 lb/acre) on kentucky bluegrass (Poa pratensis) sod temperatures during the first 24 h of storage. Experimental design was completely randomized with three replications and a 2 (trinexapac-ethyl verses control) × 3 (8-h storage intervals) factorial arrangement of treatments. Trinexapac-ethyl treatments were applied 6 and 2 weeks before harvest in the first experiment and 10, 6, and 2 weeks before harvest in the second experiment. Two and three applications of trinexapac-ethyl reduced sod storage temperatures. The reduction in rate of heating in treated sod became significantly different than untreated sod within 4 h after harvest. Mean sod temperatures in both experiments were 3 °C (6 °F) cooler in treated sod after 12 h of storage than untreated sod. These results suggest that trinexapac-ethyl could be used by sod growers to extend storage times and increase shipping and market areas. A multiple application program can enable sod growers to maximize the enhancement effects of trinexapacethyl on sod storage life.

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Neil L. Heckman, Garald L. Horst and Roch E. Gaussoin

Buffalograss [Buchloë dactyloides (Nutt.) Engelm.] is a warm-season perennial grass native to the North American Great Plains region and has been used as a low-maintenance turfgrass. Turf-type buffalograsses are available and are commonly used on nonirrigated land. Our objectives were to determine the deepest planting depth of burrs that would allow acceptable emergence, and to evaluate planting depth effects on buffalograss seedling morphology. Two greenhouse experiments were conducted in Fall 2000. Experimental design was a randomized complete block with 4 replications and a 3 (cultivar) × 6 (planting depth) factorial treatment arrangement. Results showed that buffalograss emergence decreased as planting depth increased. All cultivars had <10% total emergence at planting depths >50 mm. Emergence rate indices were greatest when planting depth was 13 mm and were significantly lower at planting depths of 51 and 76 mm. Average coleoptile length was 11 mm. Coleoptile length was similar between all planting depths except for the 13 mm depth which resulted in 9-mm-long coleoptile. Subcoleoptile internode length increased with planting depth up to 38 mm. Planting depths deeper than 38 mm did not significantly increase subcoleoptile internode length.

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Amy L. Neigebauer, Greg L. Davis, Garald L. Horst and Donald H. Steinegger

Field-grown wildflower sod has been in production for several years, but as with any crop management system, the reasoning behind the methods is not always known. One characteristic of wildflower sod production that has been debated is the height at which the plant is maintained. The above-ground shoot growth is managed to reduce the damage to plants when undercut and to allow for ease of shipping. Growers typically use a height of 7.6 cm because this is the highest height allowed by many mowers. Also, root production is the key to forming a sod that will hold together well and withstand the rigors of undercutting, lifting, storage, and transplanting. The purpose of this study was to determine the influence of cutting height on the plant's ability to produce a sod. Rudbeckia hirta L. was used as a model wildflower species and was seeded into polyvinyl chloride (PVC) tubes 10.2 cm in diameter with a depth of 60 cm to simulate a field situation. To characterize shoot and root growth, during a period of 12 weeks plants either received no clipping or continuous clipping at heights of 5.1, 7.6, and 10.2 cm. Root dry weights were measured at depths of 0-2.54, 2.54-21.7, 21.7-40.8, and 40.8--60.0 cm. Leaf area measurements of the clippings were recorded to determine productivity. Results indicated that clipping the shoots of Rudbeckia hirta caused a decrease in root biomass.

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Amy L. Neigebauer, Garald L. Horst, Donald H. Steinegger and Greg L. Davis

Significant research has been conducted on wildflower sod, but the reasoning behind the production system methods is not clear. The purpose of this research was to determine the influence of mowing height on the subsequent leaf growth and root biomass distribution in a wildflower sod production system. Rudbeckia hirta was grown in sand in polyvinyl chloride (PVC) tubes in simulating field conditions. Plants were either not mowed (control) or hand-clipped to 5.1, 7.6, or 10.2 cm to simulate mowing. After the initial mowing, plants were mowed at ≈7-day intervals. Total root depth, number of root axes in the top 2.5 cm, root: shoot ratio, total root dry weight, and root dry weight at depths of 0.0-2.5, 2.5-21.7, 21.7-40.8, and 40.8-60.0 cm were measured at the end of the study. Comparing the total root dry weight of all segments indicates that mowing significantly reduces root biomass. As mowing height increased, the depth of longest root increased linearly. Plants not mowed or plants mowed to 10.2 cm produced significantly more root axes in the top 2.5 cm of sand than did mowing heights of 5.1 or 7.6 cm. Root dry weight in the top 2.5 cm was considerably greater in nonmowed plants. Increased root axes in sod with higher mowing heights indicated a greater root density, which may also increase wildflower sod stability.

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Neil L. Heckman, Garald L. Horst, Roch E. Gaussoin and Linda J. Young

Heat accumulation during storage of sod may reach lethal temperatures within 4 days, decreasing sod quality. Treatment with trinexapac-ethyl reduces heat accumulation during sod storage. However, heat tolerance of grasses treated with trinexapacethyl has not been documented. Our objectives were to: 1) determine the lethal temperatures for Kentucky bluegrass (Poa pratensis L.); and 2) identify the effect of a single application of trinexapac-ethyl on heat tolerance. Experimental design was a randomized complete block with three replications and a two (trinexapac-ethyl vs. control) × two (cultivars) factorial arrangement of treatments. Ten days after chemical treatment, Kentucky bluegrass sprigs were exposed to heat stress for 4 days in a temperature gradient block under low vapor pressure deficit. Treatment with trinexapac-ethyl at 0.23 kg·ha-1 reduced heat tolerance. Temperature needed to kill 50% of the population was 35.5 °C for treated vs. 36.1 °C for nontreated grass. Trinexapac-ethyl is in the same chemical family as the cyclohexanedione herbicides that interfere with lipid syntheses in grasses. This may be a reason for the slight decrease in heat tolerance. The practical value of trinexapac-ethyl treatment in reducing heat accumulation during storage of sod may be partially negated by a decrease in heat tolerance. Chemical name used: [(4-cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid methyl ester] (trinexapac-ethyl).

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Catherine A. Paul, Greg L. Davis, Garald L. Horst and Steven N. Rodie

Water conservation in a landscape is an important issue because periodic water shortages are common in many regions of the world. This increases the importance of specifying landscape plants that require less water and matching the plant to site microclimates. Our objectives were to establish water-use rates for three herbaceous landscape plants and to determine the level of water reduction these plants can tolerate while maintaining both visual and landscape quality. Water use rates were determined for Schizachyrium scoparium (Little bluestem), Hosta spp. (Hosta) and Festuca cinerea `Dwarf' (Dwarf blue fescue) in studies using pot lysimeters at the Univ. of Nebraska Horticulture Research Greenhouse facility. Each lysimeter was watered to saturation, allowed to drain to field capacity, and weighed. The lysimeters were weighed again 24 h later, and the process was repeated to determine daily evapotranspiration. Results indicated that hosta used less water than dwarf blue fescue and little bluestem. In a subsequent study to compare the relative effects of withholding irrigation among these species, seven groups of five replicates of each species were grown in 1 peat: 0.33 vermiculite: 0.66 soil: 1 sand (by volume) in 7.6-L containers. Each container was watered to saturation, allowed to drain for 24 h to reach field capacity, and allowed to dry down in 10-day increments. Results of the dry-down study indicated that little bluestem maintained the best visual quality for the longest duration of drought, followed by dwarf blue fescue and hosta in decreasing order of visual quality.

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Richard A. Wit, Garald L. Horst, Donald H. Steinegger and Blaine L. Blad

Depletion and contamination of traditional water supplies and population pressures are straining the water resources of the United States. This has placed increased emphasis on the need for water conservation through all phases of the use cycle. Objectives of this research were to: 1) Determine water use in residential, commercial, and institutional landscapes; 2) Evaluate landscape irrigation system performance; and 3) Evaluate feasibility of landscape irrigation scheduling. Beginning in 1991, water meters on 18 test sites in Lincoln, NE were read on a weekly basis. Water meter readings during the winter were used to develop a baseline on non-landscape water use. The “can test” method was used to evaluate landscape irrigation system precipitation rate and distribution efficiency. Four recording weather stations were used to estimate daily potential evapotranspiration (ETp). Lysimeters (20 cm dia. × 31 cm deep) were installed in two Kentucky bluegrass and one tall fescue landscape to estimate water use coefficients for calculating landscape evapotranspiration. Irrigation system Christiansen coefficients of uniformity ranged from .43 to .87 with scheduling coefficients ranging from 1.31 to over 15.14. Poor irrigation system performance characteristics made it difficult to schedule irrigation on estimated water use.

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Neil L. Heckman, Garald L. Horst, Roch E. Gaussoin and Kevin W. Frank

Internal heating during sod storage can lead to plant deterioration and is a limiting factor in sod transportation. Storage practices such as the use of refrigeration and vacuum packaging have increased storage time; however, these are usually not practical or economical. Experiments were conducted to develop a feasible growth regulator management technique, using trinexapac-ethyl, to increase the storage life of Kentucky bluegrass (Poa pratensis L.) sod. Experimental setup for all experiments was a completely randomized design with a 2 (trinexapac-ethyl vs. control) × 3 (storage times) factorial treatment arrangement with 3 replications. Trinexapac-ethyl was applied at 0.23 kg·ha-1 to Kentucky bluegrass 2 weeks prior to harvesting. Results showed that sod treated with trinexapac-ethyl was as much as 10 °C cooler than the controls in the center of the sod stacks after 48 hours of storage. The reduced sod temperatures led to a 30% greater tensile strength and 17% better quality ratings in treated sod after 24 hours of storage. A preharvest application of trinexapac-ethyl appears to increase storage times of Kentucky bluegrass sod, which may improve sod market quality. Chemical name used: [4(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] (trinexapac-ethyl).

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Kenton W. Peterson, Robert C. Shearman, Roch E. Gaussoin, Garald L. Horst and Walter H. Schacht

Attempts to establish buffalograss [Buchloë dactyloides (Nutt.) Engelm.] turfs from sprigs have been limited and successful stand establishment has been inconsistent. This study was conducted to determine whether accumulated growing degree-days (GDD) and cultivar of harvested sprigs have an effect on buffalograss sprig establishment. Two field studies were conducted on a Tomek silty-clay loam (fine smectitic mesic Pachic Agriudolls) in 2007 and again in 2008. The cultivars Legacy, a hexaploid, and Prestige, a tetraploid, were used in this investigation. Sprigs were harvested and planted on 29 June, 17 July, 31 July, and 15 Aug. in 2007 and 15 May, 4 June, 19 June, 2 July, 21 July, 31 July, and 18 Aug. in 2008. The GDDs were back-calculated from these harvest dates. The harvest date of the sprigs represented 1050, 1380, 1670, and 1980 GDD in 2007 and 120, 380, 620, 840, 1200, 1400, and 1720 in 2008. Aboveground buffalograss phytomass and percent buffalograss groundcover data were collected in 2007 and 2008. In 2008, total available sugar and starch content of harvested sprigs were determined for each sprig harvest date. In the 2007 studies, sprigs harvested at 1050 GDDs resulted in the best establishment for both cultivars. In the 2008 studies, ‘Legacy’ established successfully through 840 GDDs, and ‘Prestige’ established through 1200 GDDs. Sugar or starch content did not appear to influence sprigging success. These results support the recommendation to establish buffalograss from sprigs harvested before 1050 GDDs for best results.

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Ty A. McClellan, Roch E. Gaussoin, Robert C. Shearman, Charles S. Wortmann, Martha Mamo, Garald L. Horst and David B. Marx

Nutrient and chemical changes in turfgrass sand-based root zones are not well understood. This study was conducted to characterize nutrient and chemical properties in putting greens influenced by root zone mixture and establishment treatment, putting green age, and soil depth. Putting greens were constructed and established with Agrostis stolonifera L. in sequential years from 1997 to 2000. Treatments included root zone mixtures of 80:20 (v:v) sand and sphagnum peat and 80:15:5 (v:v:v) sand, sphagnum peat, and soil, and accelerated versus controlled establishment. In the establishment year, the accelerated treatment received 2.6-, 3.0-, and 2.6-fold more nitrogen, phosphorus, and potassium, respectively, than the controlled treatment. Soil samples were taken in Fall 2001, Spring 2004, and Summer 2004 and were analyzed for nutrient and chemical properties such as pH, cation exchange capacity (CEC), organic matter (OM), total soluble salts (TSS), and 12 nutrients. The root zone mixture and establishment treatments had minimal effects on most nutrient and chemical properties with the exception of phosphorus and pH. Cation exchange capacity, OM, TSS, and all nutrients decreased with soil depth, whereas soil pH increased. The putting green age × soil depth interaction was significant for many of the nutrient and chemical properties, but separating soil samples into mat and original root zone instead of predetermined soil sampling depths eliminated most of these interactions. The mat layer had higher CEC and OM values and nutrient concentrations and lower pH values than the original root zone mixture.