Copyright (c) 2010 All rights reserved. http://works.bepress.com/dwehner Recent documents in David J. Wehner en-us Wed, 21 Jul 2010 13:16:21 PDT 3600 http://works.bepress.com/dwehner/25 http://works.bepress.com/dwehner/25 Tue, 06 May 2008 16:58:42 PDT Iron applications are sometimes used to enhance the color (darker green) of turfgrass stands even when iron is not deficient. A study was conducted to determine the feasibility of replacing a portion of the total yearly N applied to Kentucky bluegrass (Poa pratensis L.) with iron. Turfgrass response to iron chelate (Sequestrene 330) applications at 2.2 kg Fe ha-1 in combination with three liquid-applied N sources (urea, Formolene, and FLUF) at 25 kg N ha-1 was compared to turf response from applications of the N sources at 49 kg N ha-1. Iron was substituted for part of the N in either the first and second, second and third, or third application in a four application per year program. The study was conducted for three years, and the fertilized turf was rated for color weekly during the growing season. Depending on N source and frequency of Fe application, turf treated with N received higher color ratings compared to turf receiving Fe + N on 13 (Formolene + Fe in third application) to 36% (Fluf + Fe in first and second application) of the rating dates. Turf color was judged acceptable on 78 to 85% of the rating dates for turf treated with N and 62 to 85% of the rating dates for turf treated with Fe + N. The results indicate that it is feasible to substitute iron for a portion of the N in a urea or Formolene fertilization program but that caution should be used when replacing N from FLUF with iron. David J. Wehner Turfgrass Management http://works.bepress.com/dwehner/24 http://works.bepress.com/dwehner/24 Wed, 30 Apr 2008 15:06:00 PDT A microecosystem was designed to study the behavior of pesticides, fertilizers, or related compounds applied to plant stands. The system consists of three parts: a brass base that holds the plant growth media, a glass atmospheric chamber that rests on the base, and a set of analytical traps. The brass base is fitted with a porous ceramic plate so that tension can be applied to the water in the growing media. Air enters the bottom of the glass atmospheric chamber and exits through the top into appropriate trapping systems to recover volatilized pesticides, ammonia, or metabolized 14CO2 from labeled compounds. A port at the base of the chamber allows collection of leachate. The microecosystem was evaluated by applying N sources or a pesticide to intact turfgrass profiles and monitoring the fate of the applied compound. Leaching and volatilization losses of N ranged from 0 to 17% and 0.1 to 17% of the applied N, respectively, depending on N source, soil conditions, and whether tension was applied to the base of the system. Three weeks after the application of radiolabeled diazinon [O,O-diethyl-0-(2-isopropyl-4-methyl•6primidinyl) phosphorothiote] to a turf, 47% of the label remained in the form of the parent compound, 22% had been metabolized and lost as 14CO2, 1% had leached through the profile, 2% had been lost through volatilization, and 28% remained in the soil as a metabolite or in unextractable compounds. The microecosystem has proven to be an invaluable tool for turfgrass research and should be useful for fertilizer and pesticide fate studies with other crops. B. E. Branham Turfgrass Management http://works.bepress.com/dwehner/23 http://works.bepress.com/dwehner/23 Wed, 30 Apr 2008 15:04:35 PDT Diazinon (0,0-diethyl-0-(2-isopropyl-6-methyl-4-primidinyl) phosphorothioate) is widely used to control turfgrass insect pests. Poor control of soil-inhabiting insects has been found where diazinon has been applied to thatched turfgrass stands. The purpose of this study was to evaluate the environmental fate of diazinon applied to turfgrass stands. A microecosystem was used to follow the fate of radiolabeled diazinon surface applied to Kentucky bluegrass (Poa pratensis L.) turfs, with or without a thatch layer, growing on Flanigan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) irrigated daily or every 4 days. Loss of diazinon by volatilization, leaching, and degradation accompanied by release of 14CO2 or incorporation of label into soil compounds was measured. The most degradation of parent compound occurred on turf containing a thatch layer irrigated daily where only 7% of the applied diazinon remained after 3 weeks. Between 32 and 47% of the parent compound remained in either turf with thatch irrigated every 4 days or turfs without thatch. The majority of the diazinon (96%) remained in the top 10 mm of the turf profile regardless of whether this was thatch or soil. In the presence of thatch, there was an accelerated rate of diazinon degradation as measured by release of 14CO2 from the two position on the pyrmidine ring. Increasing irrigation frequency on the thatched turf did not cause an increase in leaching but did increase diazinon breakdown. The results of the study suggest that where thatch is present, reduced control of insects is due both to a failure of the insecticide to move through the thatch and an increased rate of degradation. B. E. Branham Turfgrass Management http://works.bepress.com/dwehner/22 http://works.bepress.com/dwehner/22 Wed, 30 Apr 2008 10:57:17 PDT Denitrification may represent an important mechanism in the fate of N applied to turf. Denitrification losses were directly measured from fertilized 'Baron' Kentucky bluegrass (Poa pratensis L.) sod samples sealed in acrylic chambers using the acetylene inhibition technique. Losses were correlated with soil texture, percent soil saturation (SAT), and temperature. Losses from turf on a Hadley silt loam soil and Hadley silt soil (both coarse-silty, mixed, nonacid, mesic Typic Udifluvents) incubated at 22°C did not exceed 0.4 and 0.1%, respectively, of the applied potassium nitrate fertilizer (4.5 g N m-2) when soil water levels were less than 75% saturated. Soil saturation increased denitrification losses from the silt loam and silt soils to 2.2 and 5.4% of the applied N, respectively. The relationship between percent soil saturation and denitrification loss was quadratic and highly significant for both soils. The equations are: milligrams of N2O – N m-210 d-1 = 1432.50 – 38.96 (percent SAT silt soil) + 0.26 (percent silt soil)2 or 130.80 -5.40 (percent SAT silt loam soil) + 0.05 (SAT silt loam soil)2. A linear relationship [milligrams of N2O m-2 10 d-1 = 0.49(°C) – 9.70] existed between denitrification losses and soil temperatures between 22 and 30°C in the silt soil at 75% of soil saturation. Soil temperatures of 30°C or greater coupled with saturated soil conditions resulted in the greatest losses, equivalent to 44.6 and 92.6% of the applied N to the silt loam and silt soils, respectively. Denitrification losses did not increase at soil temperatures above 30°C. These results indicate that denitrification loss from fertilizers applied to turfgrasses may not be a serious problem unless the soils are saturated and at higher soil temperatures. C. F. Mancino Turfgrass Management http://works.bepress.com/dwehner/21 http://works.bepress.com/dwehner/21 Wed, 30 Apr 2008 09:35:07 PDT The quality of cool-season turfgrasses frequently declines during periods of high temperature stress. Simple tests are needed to rapidly identify heat tolerant germplasm for incorporation into breeding programs. Facilitative screening tests have been devised, however, in the few studies that have been performed only immature and greenhouse or growth chamber-grown plants have been evaluated. To be of practical value, results of screening tests, employing plants grown under artificial conditions, should correlate closely with results of tests involving field grown plants. The objective of this research was to evaluate the heat tolerance of several cultivars of Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.) grown in the field under four different regimes of N fertilization (0, 98,148, or 196 kg ha-1 yr-1) in a Typic Hapludults, fine silty, mixed mesic soil for comparison with published results in which greenhouse and growth chamber-grown material was used. On six sampling dates, plants representing all cultivar and N combinations were exposed to 42, 44, and 46°C by immersion in a water bath. Heat tolerance of the cultivars was compared using the mean percent recovery weight for the three temperatures. The Kentucky bluegrass cvs. Sydsport, Vantage, and Pennstar were more heat tolerant than the perennial ryegrass cvs. Pennfine, Citation, and Caravelle. When data were averaged over 2 years, it was shown that Sydsport was significantly more heat tolerant than all other genera and cultivars tested. Pennfine had higher recovery weights than the other two ryegrasses on four of six sampling dates. When data were averaged, however, no significant heat tolerance differences among the ryegrasses were discerned. The results from the screening of field grown material followed the same trends as published results using greenhouse or growth chamber-grown samples. This investigation therefore provides strong evidence that laboratory screening tests may be used to identify accurately and rapidly heat tolerant cultivars of Kentucky bluegrass and possibly perennial ryegrass. The overall heat tolerance of the cultivars on each sampling date correlated with the amount of precipitation (r= -0.91) and the average high temperature (r=0.93) for the period just prior to and during sampling. The moderate N fertility regimes imposed had little effect on the heat tolerance of the grasses. D. D. Minner Turfgrass Management http://works.bepress.com/dwehner/20 http://works.bepress.com/dwehner/20 Fri, 25 Apr 2008 13:11:19 PDT The components of a turfgrass ecosystem, including plants, an intervening layer of thatch and the underlying soil, influence the fate of topically applied urea fertilizer. The loss of urea N by ammonia volatilization may be governed by the rate of urea hydrolysis. The main objective of this study was to determine the extent of urease activity associated with turfgrass plant tissue, thatch, and the underlying soil. This information may help elucidate the mechanism of ammonia loss following urea application. Because a turfgrass stand frequently possesses an extensive thatch layer that may serve as the primary plant growth medium, additional objectives included: i) determining the effects of air drying and seasonal variation on the activity of urease in thatch; ii) determining the variability in thatch urease activity by analyzing multiple field samples; and iii) determining the variation of urease activity within a thatch profile. Turfgrass clippings, thatch, and underlying Flanagan silt loam soil (Aquic Argiudoll) samples were taken from a field-grown Kentucky bluegrass (Poa pratensis L.) turf in either September 1980 or March 1981. On a dry weight basis, urease activity was 18 to 30 times higher from turfgrass clippings and thatch than from soil. Air drying thatch increased urease activity by 20 % over moist samples while air drying soil samples had no apparent effect. Greenhouse incubation of winter-dormant thatch samples increased urease activity 40 %, presumably in response to the duration of increased temperature. Thatch urease activity varied between sampling sites but still remained extremely high compared to soil activity. Within each thatch sample (1 X 1 X 2 cm), urease activity was highest in the upper 1.0 cm of the profile. It was concluded that thatch urease activity was variable in nature depending upon seasonal conditions which contrasts sharply with extremely stable soil urease activities. These findings suggest that, because of the high level of urease in thatch, ammonia volatilization will occur from most urea-treated turfgrass stands, regardless of the type of underlying soil unless the urea is thoroughly washed into the soil. W. A. Torello Turfgrass Management http://works.bepress.com/dwehner/19 http://works.bepress.com/dwehner/19 Fri, 25 Apr 2008 13:10:49 PDT The purpose of this article is to review some of the basic information on iron, look at one of the discoveries made during the 1980s, and present some of the published research studies that have been conducted with iron on turfgrasses. Additional information on the use of iron can be found in popular magazines and in the proceedings of turfgrass conferences. David J. Wehner Turfgrass Management http://works.bepress.com/dwehner/18 http://works.bepress.com/dwehner/18 Thu, 24 Apr 2008 16:19:23 PDT Use of cool-season turfgrasses in transitional environments is limited, in part, by their heat tolerance. Development of a rapid heat tolerance screening technique would be of value in determining the potential of turf•grasses for use in warmer areas. The heat tolerance of 22 Kentucky bluegrass (Poa pratensis L.) cultivars, Poa annua L., and four perennial ryegrass cultivars (Lolium perenne L.) was evaluated by exposing plants for 30 min to temperatures ranging from 41 to 49 C in single degree intervals. Ten-week-old plants, which had been grown under a low level of N fertilization and watered infrequently to maximize heat tolerance development, were sealed in plastic bags, placed in a constant temperature water bath for treatment, and then replanted. Recovery was evaluated by visually rating the plants 4 weeks after treatment or by harvesting and weighing plants 2 weeks after treatment and expressing the weight as a percentage of the weight of a non-stressed control (referred to as recovery weight). Cultivar comparisons were based on the average recovery weight over a given temperature range. Initial injury occurred at 41 to 43 C with complete kill at 47 to 49 C. Kentucky bluegrass was more heat tolerant than Poa annua L. and perennial ryegrass. Heat tolerance of the latter two species was approximately equal. The Kentucky bluegrass cultivars tested were similar in heat tolerance. Among the ryegrasses, 'Loretta' was less heat tolerant than 'Diplomat', 'Pennfine', and 'Citation'. Of all the grasses, 'Sydsport' Kentucky bluegrass ranked the highest and Loretta perennial ryegrass the lowest in heat tolerance. The correlation between dilute acid extractable carbohydrate reserves and recovery weight for these five cultivars was not significant. There was a significant negative correlation between recovery weight and Fe and Al concentration. David J. Wehner Turfgrass Management http://works.bepress.com/dwehner/16 http://works.bepress.com/dwehner/16 Thu, 24 Apr 2008 15:53:00 PDT Because of the importance of such factors as appeorance and vigor in turf management, genetic selection of Kentucky bluegrass (Poa pratensis L.) is often conducted at high levels of N application. This process can mask potential differences between genotypes in N efficiency, especially under low N levels. The case is also made that because soil is the medium in which plant selections ultimately must perform, cultivar screening for N efficiency in solution culture should relate to results in soil. This study was conducted to evaluate N-utilization efficiency (NUE – mg plant dry matter mg-1 plant N) in six bluegrass cultivars at low (0.2, 0.7 mM NO3-N) and high (3.5 mM NO3-N) levels of N supply in nutrient solution culture (nutriculture) and soil. With high N supply, total plant N accumulation and N-root uptake efficiency (NRE-mg plant N g-1 root dry matter) increased in each cultivar, while NUE and shoot efficiency ratio (SER–mg shoot dry matter mg-1 shoot N) decreased, with the magnitude and relative response dependent on genotype and medium. As a group, as well as individually, cultivars Asset, Dawn, and Trenton were higher yielding, more responsive to increasing solution N concentration, and more efficient (NUE) at low levels of N supply than cultivars Limousine, Barzan, or Midnight. Under low N supply, NUE in nutriculture ranged from 26.2 (g plant dry weight mg-1 N) in Limousine to 40.1 in Asset, and in soil from 63.6 in Midnight to 77.4 in Asset. Differences in NUE among cultivars were more associated with shoot efficiency than with root absorption efficiency. Despite noticeably higher NUE in soil than in nutriculture, and significant effects of N fertility, genotypic differences in the various N efficiency traits in solution culture were also apparent in soil. The results suggest that NUE in Kentucky bluegrass can be enhanced by cultivar selection under low-N conditions. While the similarities of the actual N conditions between nutriculture and soil remain in question, it appears that solution culture can be used as an effective surrogate for characterizing NUE in divergent types of bluegrass cultivars. Anthony F. Bertauski Turfgrass Management http://works.bepress.com/dwehner/15 http://works.bepress.com/dwehner/15 Fri, 04 Apr 2008 17:16:36 PDT Annual bluegrass (Poa annua L.) turf quality is reduced during periods of high temperature. To predict heat stress injury and develop improved prestress maintenance practices, an understanding of the seasonal variation in annual bluegrass heat tolerance and the influence of soil moisture on heat tolerance is crucial. Annual bluegrass growing in the field on a Drummer silty clay loam (fine silty, mixed, mesic Typic Haplaquolls) was sampled on 23 dates over two growing seasons and brought to a laboratory for exposure to high temperature. Prestress environmental conditions (air and soil temperature, soil matric potential, plant water potential, daylength, rainfall and irrigation) were monitored. Plants were enclosed in plastic bags, exposed for 30 min to temperatures in the range 40 to 48°C in a water bath and placed in a greenhouse for a 2-week recovery period. The dry weight of the stressed plants expressed as a percentage of the controls (heat tolerance indices, HTI) was used as a measure of heat tolerance. In a second experiment, field plots of annual bluegrass were maintained for one growing season under either a dry (rainfall plus irrigation to prevent severe wilting) or moist (dry treatment plus 10-mm irrigation every other day) soil regime. Plants were stress-tested on five dates when differences in soil matric potentials existed between treatments, and on five dates when matric potentials were identical (saturated soil). Turfgrass color, quality, and rooting depth were monitored. The best equation fitted to HTI using the results of the first experiment was: y = 15.6 x A + 9.85 x B – 0.22 x A2 – 0.31 x B2 – 0.25 x A x B x 194.71 (R2 = 0.78, p = 0.0001), where A = mean maximum daily air temperature (°C) for the 2 days preceding sampling and B = mean total precipitation (mm) of the period 2 through 4 days prior to sampling. The second experiment revealed a non-significant trend for annual bluegrass maintained under moist soil conditions to be less heat tolerant than that under dry conditions. No differences were found due to treatment in rooting depth which negatively correlated (r = –0.83) with the soil temperature at 10 cm. Because of reduced turfgrass quality with the dry soil conditions, there appeared to be little potential for increasing heat tolerance through irrigation management. Dennis L. Martin Turfgrass Management http://works.bepress.com/dwehner/14 http://works.bepress.com/dwehner/14 Fri, 04 Apr 2008 17:16:32 PDT An understanding of the natural variation in heat tolerance of Kentucky bluegrass is needed to develop predictive models for stress tolerance. The variation in heat tolerance of ‘Adelphi’ Kentucky bluegrass (Poa pratensis L.) over the growing season and the effect of recovery environment on the perceived heat tolerance of the plants was determined. Field-grown plants (Chillum silt loam, fine-silty, mixed, mesic Typic Hapludults) were exposed to heat stress on 11 dates over two growing seasons by immersion in a water bath for 30 min at either 42, 44, or 46°C and then placed in either a greenhouse, or one of two growth chamber environments (35/22 or 22/15°C day/ night temperature) for a 2-week recovery period. The dry weight of the stressed plants expressed as a percentage of the controls (recovery weight) was used as a measure of heat tolerance. Heat tolerance increased from May to July and then decreased from August to October. A significant relationship existed between heat tolerance, day length (D) and average low temperature (LT) for the sampling dates (y - 128.65*D - 5.67*D2 - 14.46*LT - 0.49*LT2 + 2.21*D*LT - 743.86, R2 = 0.95, P = 0.003). Recovery weights for plants in the greenhouse were not significantly different from recovery weights for plants in either of the other two recovery environments on 10 of the 11 sampling dates. David J. Wehner Turfgrass Management http://works.bepress.com/dwehner/13 http://works.bepress.com/dwehner/13 Fri, 04 Apr 2008 17:16:29 PDT A greenhouse study was conducted in a hydroponic system to determine the nitrogen (N) utilization efficiency (NUE) of 14 creeping bentgrass cultivars. There were significant differences among cultivars in plant tissue dry weight, tissue N content, root absorption efficiency (RAE), and NUE. Considering all plant tissue (whole plant), 'Penncross' accumulated the highest N accompanied with the highest whole plant dry weight (WPDW), while 'Allure' accumulated the lowest total Nand WPDW than all the other cultivars. The proportion of WPDW and total N partitioned to shoots was higher than partitioned to roots in each cultivar. On a whole plant basis, 'Regent' had the highest NUE while 'Allure' had the lowest NUE. N absorption efficiency values were comparatively higher in 'Allure' than any of the other cultivars, while 'Forbes' had the lowest RAE. The RAE value of the cultivars was not a response to the NUE indicating that differences in RAE was not a critical factor involved in genotypic differences in NUE. Differences in NUE among most cultivars were correlated to plant dry weight in a second experiment. Solution systems have the potential for an effective means of screening the NUE of creeping bentgrass cultivars. Y. Kuo Turfgrass Management http://works.bepress.com/dwehner/12 http://works.bepress.com/dwehner/12 Fri, 04 Apr 2008 17:16:26 PDT The goal of the professional lawn care industry is to provide the homeowner with a dark green weed-free lawn. Members of this industry are interested in techniques to enhance the color of a turfgrass stand in lieu of excessive N fertilization. The purpose of this research was to evaluate the use of foliar applications of Fe alone or in combination with N on the color response of Kentucky bluegrass (Poa pratensis L.). Iron sulfate or an iron chelate was applied at the rate of 1.1, 2.2, or 4.5 kg Fe ha–1 in combination with either 0, 25, or 49 kg N ha–1 to a mixed ‘Columbia’/‘Touchdown’ Kentucky bluegrass turf growing on a Catlin silt loam (fine-silty, mixed, mesic Typic Argiudoll). Color ratings and clipping weights were determined on a weekly basis until treatment effects were no longer significant. In a separate experiment, both sources of Fe were applied at rates of 1.1 to 72.4 kg Fe ha–1 to Kentucky bluegrass to evaluate phytotoxicity. The color enhancement due to Fe applications without N lasted from several weeks to several months depending on the weather following application. Use of Fe during cool wet periods enhanced turf color for only 2 to 3 weeks and therefore, was considered of limited value. Iron applications during cool dry periods enhanced turf color for several months. The treatment of 2.2 kg ha–1 of Fe from iron chelate was judged to be the most effective Fe treatment because the color enhancement was usually equal to that provided by a 4.5 kg rate of either source but it did not result in any discoloration as was found with the 4.5 kg rate. Combining Fe with the 25 kg ha–1 rate of N resulted in color enhancement equal to that caused by applying 49 kg ha–1 of N alone. The results of the study indicate that combining Fe with N can result in acceptable turfgrass color with lower rates of N. No permanent damage was caused to turfs receiving Fe at rates up to 72.2 kg ha–1 although foliar phytotoxicity was observed. A. K. Yust Turfgrass Management http://works.bepress.com/dwehner/11 http://works.bepress.com/dwehner/11 Fri, 04 Apr 2008 17:16:22 PDT Nitrogen applied to turfgrass stands can be lost through leaching, denitrification, or ammonia (NH3) volatilization. The purpose of this investigation was to evaluate the effects of N carrier and mode of application on NH3 volatilization from a Kentucky bluegrass (Poa pratensis L.) turf growing on an acidic (pH 6.4) Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil. The NH3, which volatilized after application of any of several sulfur-coated ureas (SCU), prilled urea, spray-applied solubilized urea, and two liquid N products was measured by passing the airstream from microecosystems, in which the treated turfs were growing, through an indicating boric acid solution to trap NH3. Ammonia-N losses after sulfur-coated urea fertilization ranged from 0.2% of the applied N when the fertilization rate was 98 kg N/ha to 2.3 % of the applied N when the fertilization rate was 293 kg N/ha. When prilled urea was applied at a rate of 293 kg N/ha, NH3 losses averaged 10.3% of the applied N whereas 4.6 and 1.6% of the applied N was lost after turf was fertilized with 49 kg N/ha from spray-applied solubilized urea and prilled urea, respectively. Ammonia losses from turf treated with liquid N sources ranged from 3.2 to 4.5% of the applied N. The results of this research indicate that ammonia volatilization occurs to a limited extent in turfgrass stands growing on an acidic soil. W. A. Torello Turfgrass Management http://works.bepress.com/dwehner/10 http://works.bepress.com/dwehner/10 Fri, 04 Apr 2008 17:16:19 PDT Turf managers sometimes experience poor or early loss of control of targeted weeds, even when herbicides are applied at recommended rates. This study was conducted to determine the influence of soil temperature and moisture on the rate of DCPA (dimethyl tetrachloroterephthalate) degradation in soil. The effect of six soil temperatures, three soil moistures, and three soil textures on the degradation of DCPA was measured in the laboratory through HPLC analysis. Soil temperature influenced the rate of DCPA degradation in the following order: 10<<15<<20<25=30>35°C. The average half-life ranged from 92 d at 10°C to 18 d at 30°C. Soil moisture content influenced the rate of degradation in the following order: low (0.1 kg H2O kg-1 soil) medium (0.2 kg H20 kg-1 soil) = high (0.4 kg H2O kg-1 soil). The average half-life values of DCPA were 49, 33, and 31 d for the low, medium, and high soil moisture levels, respectively. A mathematical model of DCPA loss was utilized to determine the relative contribution of time, soil moisture, and soil temperature to the rate of degradation. Faster degradation of DCPA was observed from a sand/soil moisture (47.5:52.5, w/w) than from either a sand or a soil (Flanagan silt loam [fine, montmorillonitic, mesic Aquic Argiudoll]). It was concluded that the dissipation rate of DCPA is largely dependent on soil environmental conditions including soil temperature, soil moisture, soil texture, and the time interval since the application to the soil. Thus, it is suggested that soil environmental factors be considered in determining the timing of second or subsequent applications when necessary rather than following a fixed application schedule. J. S. Choi Turfgrass Management http://works.bepress.com/dwehner/9 http://works.bepress.com/dwehner/9 Fri, 04 Apr 2008 17:16:16 PDT An essential component of an introductory turfgrass management course is the description of how turfgrass species are adapted to different cultural systems and environments. The objectives of this project were to develop an interactive program to introduce the characteristics of turfgrass species and their optimum environments and to evaluate the students' gain in understanding turf species characteristics through this approach. A self-contained application, Turf Species, was constructed using the SuperCard development tool. Turf Species consists of three sections including a self-paced tour of the species, a what if establishment section, and randomly composed reinforcement quizzes with automatic grading. Turf Species was designed to be distributed to students on diskette for self-paced study and reinforcement of material presented during previous lectures. Each student who used the Turf Species tool spent approximately 2 h evaluating the program. Seventy-one percent of the student evaluators felt that the graphic representations or illustrations for each species aided in their understanding of the material. All of the evaluators indicated that the testing module helped in their understanding of the turf species, and 86% of them suggested that the Turf Species program should be used more extensively in the introductory turfgrass management course. An evaluation of the test scores found on returned diskettes showed an average examination grade of 52% with a range from 5 to 100%. T. W. Fermanian Turfgrass Management http://works.bepress.com/dwehner/8 http://works.bepress.com/dwehner/8 Fri, 04 Apr 2008 17:16:12 PDT Many turfgrass managers apply a portion of the total yearly N to cool-season turfgrasses in the late fall (November). The purpose of this field study was to compare fertilization programs with and without N applications in November using both slow-release and soluble N sources. Turfs of two different cultivars of Kentucky bluegrass (Poa pratensis L. cv. Baron and cv. Newport) growing on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) received 10 fertilization programs utilizing urea, isobutylidene diurea (IBDU), or sulfur-coated urea (SCU). Urea was applied four times per year with either a spring application or a late-fall application combined with applications in early June, mid-July, and early September (171–196 kg N ha–1 yr–1). For IBDU and SCU, application dates and N rates (kg ha–1) consisted of June 98 + September 98, June 98 + November 98, and June 49 + September 49 + November 74. The turfs were rated for color for 3 yr, and clipping weights were determined weekly for the final 2 yr of the study. Results were generally similar for both cultivars, except fewer significant differences in spring color ratings were found on Newport. An application of urea in November, without a subsequent spring fertilization, resulted in higher turf color ratings in the early spring but lower turf color ratings in May and June, compared to turf receiving a spring fertilization. Results indicate that a late-fall application of urea may not eliminate the need for spring fertilization but may allow a reduction in the amount of N applied in spring. Turfs fertilized with SCU in November received higher color ratings in the spring than did turf fertilized with SCU in September. With IBDU, the June + September program resulted in the highest number of ratings with acceptable turf color. November IBDU applications did not result in higher color ratings in the spring and resulted in inefficient use of the N applied. David J. Wehner Turfgrass Management http://works.bepress.com/dwehner/7 http://works.bepress.com/dwehner/7 Fri, 04 Apr 2008 17:16:09 PDT N utilization, including plant dry weight (DW) production, total N and nitrate N (NO3-N) content accumulation, N utilization efficiency (NUE), root absorption efficiency (RAE), reduced N accumulation, and nitrate assimilation capacity (NAC) were determined for creeping bentgrass cultivars grown in hydroponic culture. Possible mechanisms affecting N utilization including nitrate reductase activity (NRA) and root morphology were also examined. Four cultivars, selected from an initial screening of creeping bentgrasses were grown under both low and high levels of N in a flowing solution culture system. The relationship between NUE and plant growth for two different creeping bentgrass cultivars was investigated through tissue culture. The results indicate a genotypic variation in N utilization and absorption. The NAC was not the primary factor involved in genotypic differences in NUE. However, NRA was probably one of the mechanisms for the regulation of NUE. N utilization was affected by the level of N supplied level and environmental conditions. Plants grown under low levels of N had longer roots compared to plants grown under medium or high levels of N for either cultivar. The results suggest that root formation was probably one of the mechanisms for regulating the nitrate utilization in creeping bentgrass. Y. Kuo Turfgrass Management http://works.bepress.com/dwehner/4 http://works.bepress.com/dwehner/4 Fri, 04 Apr 2008 17:16:00 PDT Solution and suspension N sources have been developed as substitutes for urea in spray solutions used by lawn-care professionals. A field study was conducted to evaluate the response of Kentucky bluegrass (Poa pratensis L.) growing on a Catlin silt loam (Typic Argiudoll), to applications of the new solution and suspension N sources, alone or combined with urea, by comparison to turf response from application of the traditional fertilizer materials ammonium nitrate (AN), Nitroform (ureaform), sulfur-coated urea (SCU), ammonium sulfate (AS), granular urea, spray-applied urea (US), and urea-ammonium nitrate (UAN) solution. Also, urea and AS treated with dicyandiamide (DCD) were compared to the untreated sources. Fertilization rate was 195 kg N ha–1 yr–1 split into four applications except SCU which was applied twice. Turfgrass color and clipping production were monitored along with thatch accumulation and soil pH. In a second field experiment, foliar burn potentials of the new N sources were evaluated by comparison to burn potentials from US, UAN, and a liquid 12-1.8-3.3 fertilizer. Turf response to Formolene (solution N source) paralleled that due to US. Turf treated with US received higher color ratings than did that treated with Nitroform or FLUF (suspension N source) during the early growing season but this trend was reversed by late summer. Turf fertilized with FLUF resembled turf fertilized with Nitroform but was inferior to turf fertilized with SCU. There was no benefit from the inclusion of DCD with either AS or urea. Soil pH after 2 yr ranged from 5.3 to 6.4 and was lowest with AS treatment; thatch depth ranged from 7.0 to 19.3 mm and was greatest with AS treatment. Formolene and FLUF caused less foliar injury than did US, UAN, or the 12-1.8-3.3 fertilizer. Results from the two experiments indicated that the major advantage of using Formolene or FLUF was the reduced potential for foliar fertilizer burn. B. G. Spangenberg Turfgrass Management http://works.bepress.com/dwehner/6 http://works.bepress.com/dwehner/6 Fri, 04 Apr 2008 17:15:58 PDT Information is needed concerning the effects of different soil fertility levels on the activity of turfgrass roots in that part of the soil profile sampled for routine soil tests. In Pennsylvania, a sampling depth of 5 to 7.5 cm is suggested for established turf. A study was conducted on 'Merion' Kentucky bluegrass (Poa pratensis L.) to determine relationships among lime, phosphorus, and potassium applications; soil test results; foliar growth and elemental analysis; and root activity as determined by 32P uptake from three soil depths. In the field, soil pH values were 5.8 and 7.0, P ranged from 13 to 137 ppm, and K ranged from 0.14 to 0.43 meq./100g. Liming increased the Ca content in clippings from 0.35 to 0.42%. Phosphorus treatments increased P from 0.32 to 0.44%, and K was increased from 2.00 to 2.45% by K fertilization. Clipping yield was increased by P treatments. Sod plugs from the field were used in the greenhouse to determine root activity. Agar discs containing 32P were placed at a depth of 1.3, 3.8, or 6.4 cm, and the clippings were assayed for 32P after 20 and 33 days. Shallow placement of 32P resulted in more absorption. A soil P x depth interaction was found for 32P absorption. A significant positive correlation between soil P and 32P absorption was obtained for the 1.3 cm depth, whereas a nonsignificant correlation was found for the 6.4 cm placement. Results indicated that P enhanced rooting, and the magnitude of absorption from the 1.3-cm depth exemplified the need for P near the soil surface for optimum turf establishment. T. L. Watschke Turfgrass Management