In 1992, a cultivar trial was initiated in Columbus, Ohio to evaluate differences in establishment and long-term performance of cultivars of tall fescue (Festuca arundinacea), creeping red fescue (F. rubra), chewings fescue (F. rubra ssp. fallax), hard fescue (F. brevipila), kentucky bluegrass (Poa pratensis), rough bluegrass (P. trivialis), and perennial ryegrass (Lolium perenne) under low maintenance conditions in a shaded environment. Fertilizer and supplemental irrigation were applied until 1994 to establish the grasses, after which no supplemental irrigation, or pesticides were applied and fertilizer rates were reduced to 48.8 kg·ha-1 (1 lb/1000 ft2) of N per year. Percentage cover and overall quality data were collected in 2000 and compared with data collected in 1994. Initial establishment success does not appear to be a good predictor of long-term success of a cultivar in a shaded environment. There was some variability in cultivar performance under shade within a given turfgrass species. The tall fescue cultivars, as a group, had the highest overall quality and percentage cover under shade, followed by the fine fescues, kentucky bluegrass, rough bluegrass, and perennial ryegrass cultivars.
D.S. Gardner and J.A. Taylor
H.J. Hill, Jesse D. Cunningham, Kent J. Bradford, and A.G. Taylor
The Ellis-Roberts seed viability equation is used to predict seed survival after storage at specified temperatures and moisture contents. Seed priming, which can break dormancy and accelerate germination, can also reduce seed storage life. Because primed seeds were not used in developing the Ellis-Roberts equation, the reciprocal nature of specific seed moisture content (MC, fresh weight basis) and temperatures that applies to nonprimed lettuce (Lactuca sativa L.) seeds may not apply to primed seeds. To determine how priming affects lettuce seeds in relation to the viability equation, an experiment was conducted using two cultivars, ‘Big Ben’ and ‘Parris Island Cos’. Seeds primed in polyethylene glycol 8000 (–1.45 MPa, 24 h at 15 °C) and nonprimed seeds were first adjusted to 6% and 9% moisture contents and then stored at 48 and 38 °C for up to 30 days, respectively. These storage conditions (6% MC and 48 °C; 9% MC and 38 °C) were predicted by the viability equation to result in equal longevities. Subsequent viability assays at 20 °C revealed that nonprimed seeds in both storage environments exhibited similar losses in viability over time, thus validating the Ellis-Roberts equation and the use of these conditions to apply different but equal aging stress. Primed seeds of both cultivars deteriorated faster than nonprimed seeds as expected. However, primed seeds did exhibit different rates of deterioration between the storage environments. Primed seeds stored at 9% MC and 38 °C deteriorated faster than primed seeds stored at 6% MC and 48 °C. The rate of decline in probit viability percentage was three times greater in primed ‘Big Ben’ seeds stored at 9% MC and 38 °C than for those stored at 6% MC and 48 °C (–1.34 versus –0.26 probits per day, respectively). ‘Parris Island Cos’ seeds stored at 9% MC and 38 °C had twice the rate of deterioration that those stored at 6% MC and 48 °C (–1.19 and –0.49 probits per day, respectively). The results indicate that primed lettuce seeds were more sensitive to the adverse effects of higher seed MC than were nonprimed seeds during storage at elevated temperatures.
A.G. Taylor, J. Prusinski, H.J. Hill, and M.D. Dickson
Water is pervasively involved in the life cycle of seeds. Water in the environment, either as a vapor or liquid, directly affects seed moisture status. This article is devoted to the study of seed moisture status in postharvest events. Two topics are discussed: imbibitional chilling injury and upgrading of primed seeds. Imbibitional chilling injury is a physiological disorder that occurs in large-seeded legumes as well as other important agronomic seeds. Imbibitional chilling injury has been shown to reduce the survival rate of seedlings. Surviving seedlings have less emergence force per seedling and require a longer period to generate maximum force. Rapid hydration has been shown to induce injury at a particular seed moisture level. Methods of regulating the hydration rate were explored to alleviate chilling injury in snap beans (Phaseolus vulgaris L.) Plant breeding lines with the semihard seed characteristic delayed the onset of imbibition when the initial moisture level was low (8%). Coating seeds with polymeric films to complement the permeable testa retarded the imbibition rates. Both approaches alleviated chilling injury and improved seedling establishment under stressful conditions. Seed priming is a technique for elevation of seed moisture content before sowing. Primed seeds generally emerge more quickly than nonprimed seeds, especially under stressful environmental conditions. An additional merit of this technique is that it gives access to seeds with elevated moisture content. Various approaches may be employed to condition seeds after priming, but before redesiccation. Discarding the low-density fractions of primed tomato and lettuce seeds improved the percentage of germination compared with nonprimed seeds. Physiological mechanisms are presented to explain the association of density with seed viability in lettuce (Lactuca sativa L.).
Milton D. Taylor, Sarah A. White, Stewart L. Chandler, Stephen J. Klaine, and Ted Whitwell
Substantial quantities of water and nutrients are required for the production of high value nursery and greenhouse crops. As water quality criteria are strengthened locally and nationally, horticultural enterprises will have to meet stricter limits on nutrients in discharge water. This study examined the efficacy of an established vegetated surface-flow constructed wetland to mediate nitrogen (N) and phosphorus (P) in runoff water from a commercial nursery over a period of 38 months. Maximum oxidized nitrogen [nitrate-N (NO3-N) + nitrite-N (NO2-N)] inputs occurred during the spring fertilization period of March through May (11.1 to 29.9 mg·L–1 N) and minimum inputs occurred during winter plant dormancy between December and February (2.8 to 5.2 mg·L–1 N). Nitrogen remediation efficiency averaged 94.7% for March through November sampling dates but declined to a mean of 70.7% between December and February when mean wetland water temperature dropped below 15 °C. Orthophosphate phosphorus (PO4-P) concentrations in nursery runoff showed no dramatic changes over months, seasons, or years. Mean wetland influent orthophosphate concentration ranged from 0.7 to 2.2 mg·L–1 PO4-P with an overall mean of 1.41 mg·L–1 PO4-P for all months sampled. Mean discharge orthophosphate concentration ranged from 0.5 to 2.1 mg·L–1 PO4-P with a mean of 1.45 mg·L–1 PO4-P. Phosphorus remediation efficiency varied widely and there was no correlation with water temperature. This 9.31-acre surface-flow constructed wetland was highly efficient at removing N from nursery runoff from a 120-acre catchment (large container production area), although it failed to consistently lower orthophosphate levels in runoff. This type of constructed wetland is suitable for removing oxidized N forms from nursery runoff and, depending on size, is capable of handling the large volumes of runoff generated by medium to large nursery and greenhouse operations.
Milton D. Taylor, Sarah A. White, Stephen J. Klaine, and Ted Whitwell
Container-grown plants require large amounts of water and nutrients during their production cycle. This results in substantial runoff that is contaminated with nitrogen and phosphorus. At our study site, nutrients were delivered through incorporation in the potting media as timed-release prills and through liquid feeding by injection into irrigation water. Mitigation of nutrients in runoff water was dealt with proactively by the container nursery with construction of 3.77 ha of planted wetlands to receive runoff from a 48.6-ha drainage basin and excess water diverted from adjacent watersheds. Water flowed though drains between wetland cells and eventually into stilling ponds before it was allowed to exit the property. Water flow through the wetlands ranged from 1.1 to 3.1 million liters per day over the period. Three years of monitoring data indicate some seasonal differences in nitrogen removal efficiencies. Nitrogen removal between March and November averaged ≥95% while removal during winter (December through February) averaged ≥72%. Nitrogen (as nitrate) varied from 4.28 ppm to ≤0.01 ppm in wetland discharge, well below drinking water quality standards, but occasionally above levels that may cause downstream eutrophication. Orthophosphate phosphorus removal was highly variable with greatest removal occurring during late spring, late fall, and winter. There was a significant net export of phosphorus during some summer months for years 2 and 3. Phosphorus levels in wetland discharge ranged between 0.84 and 2.75 ppm. While there is currently no legal water quality standard for phosphorus, these levels were above the generally accepted level for preventing downstream eutrophication.
Robert F. Polomski, Milton D. Taylor, Sarah A. White, Ted Whitwell, Stephen J. Klaine, and William C. Bridges Jr.
Commercial nurseries use large amounts of water and nutrients during production cycles. Runoff contaminated with N and P can adversely impact surface and groundwater quality. A 3-year monitoring study of nutrient mitigation by a constructed wetland at a container nursery found nitrogen removal was highly efficient. However, orthophosphate-P removal was highly variable. Partial removal occurred during some months, but net export also occurred. P levels in wetland discharge—between 0.84 and 2.75 ppm—were well above the generally accepted level for preventing downstream eutrophication. Therefore, identifying landscape plants that remediate nutrients, especially P, could be useful in improving constructed wetlands. A 2003 greenhouse study screened commercially available landscape plants for their phytoremediation potential. Among the 17 taxa and 19 cultivars examined were woody shrubs, e.g., Cornusamomum, Myricacerifera`Emperor', and Salix integra `Hakura Nishiki'; herbaceous semiaquatics, e.g., Canna(two cultivars), Colocasia esculenta `Illustris', Rhyncospora colorata, Iris`Full Eclipse', Pontederia cordata `Singapore Pink', and Thalia geniculata `Red Stem'; and floating aquatics, e.g., Myriophyllum aquaticum, Eichhornia crassipes, and Pistia stratiotes. Plants were grown in pea gravel media and kept saturated with one of five concentrations of Hoagland's. Herbaceous and woody plants were harvested after 8 and 13 weeks, respectively. Experiments were replicated twice for each cultivar. The nutrient uptake efficiency was determined for each taxon from the total amount of N and P applied and the biomass dry weight and N and P content.