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Field research was conducted to determine the effects of N, Fe, and benzyladenine (BA) on fall performance, post-dormancy recovery, and storage nonstructural carbohydrate composition of `Midiron' bermudagrass [Cy - nodon dactylon (L.) Pers.]. Fall green color retention and turf quality were superior for 48 than for 24 kg N/ha per month. Nitrogen level did not affect post-dormancy recovery or nonstructural carbohydrate levels in stolons and rhizomes measured in Sept. and Nov. 1983 and 1984. Iron level did not influence turf color and quality during summer months. Biweekly application of 0.6 kg Fe/ha produced better retention of greenness and turf quality during Fall 1983 and 1984 and superior turf color in Spring 1985 than the 0 kg Fe/ha treatment. Better green turf coverage was obtained with the biweekly than the monthly Fe (1.2 kg-ha-l) treatment during Fall 1983. In contrast, monthly Fe produced color and turf quality similar to that of the biweekly Fe treatment during Fall 1984. Nonstructural carbohydrates were similar among Fe levels in 1983 and 1984. The effects of Fe on turf color and quality were similar at each level of N and BA. BA level did not consistently influence turf color or quality and did not affect storage carbohydrate levels. When used in conjunction with moderate summer N fertilization, foliar-applied Fe can extend bermudagrass quality during fall without adversely affecting postdormancy recovery. Chemical name used: N- (phenylmethyl)-lH-purin-6-amine (benzyladenine, BA).

Abstract

‘Tifgreen’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] was exposed to 10°/7°C (day/night) temperatures following pretreatment with 120 mg Fe/m² or 12.4 mg BA/m² to determine their effects on net photosynthesis (Pn), respiration (Rs), leaf total nonstructural carbohydrate (TNC) content, and turf color at chilling temperatures. Average Pn and Rs rates were reduced 73% and 66%, respectively, by a 72-hr chilling period. Within 2 hr at 30° following chilling, Rs rates returned to prechill rates. However, Pn rates returned to within only 50% of prechill rates during the same recovery period. The lack of full photosynthetic recovery was associated with a 288% increase in leaf TNC. Iron increased Pn rates prior to chilling. This iron effect was associated with increased photosynthetic activity per unit of chlorophyll and was evident before, during, and after the chilling period. BA increased Pn rates before chilling and within 2 hr at 30° following chilling. However, during chilling, Pn rates for the BA treatment were similar to the control. Neither Fe nor BA significantly affected leaf TNC or Rs rates. Iron and BA caused higher turf color scores during chilling. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA).

Abstract

Injury to ‘Prelude’ and ‘Manhattan II’ perennial ryegrass (Lolium perenne L.) was measured as percentage of electrolyte leakage from leaf segments after stress to determine the influence of prestress growth temperature and poststress temperature on heat tolerance. The temperature required to cause 50% cell solute efflux was 59.5°C for ‘Prelude’ and 56.5° for ‘Manhattan II’, when measured immediately after stress treatment. However, electrolyte leakage increased with time after termination of stress. When measured 24 hr after termination of stress, 52° caused 50% cell solute efflux from leaf segments of both cultivars. Injury levels 44 hr after 30 min at 50° were ≈ 12% and 89% when incubated at poststress temperatures of 7° and 35°, respectively. Incubation temperature following a 55° treatment did not affect electrolyte leakage rate in either cultivar. Greater injury occurred in both cultivars when grown at 25° than at 41°.

Incorporation of composted municipal biosolids (CMB) in low-quality soil can enhance turfgrass establishment and physical and chemical properties of turfgrass sod. The purpose of this research was to quantify CMB and fertilizer nitrogen (N) effects on Tifway bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon × C. transvaalensis Burtt-Davey] coverage, sod properties, and nutrient export in harvested sod. The experiment was conducted under field conditions in College Station, TX, from 2005 through 2008. The CMB and N effects were evaluated through digital image analysis of percentage of turfgrass coverage, gravimetric measurements of sod wet and dry weight and water content at harvest, analyses of total phosphorus (P) and total Kjeldahl N in turfgrass and soil, and computations of total P and N export through sod. Incorporation of 0.25 m³ of CMB/m³ soil and fertilizer N rates of 50 or 100 kg N/ha/application increased percentage of turfgrass cover during establishment compared with controls. At sod harvest, dry weight was less and water content was greater for CMB-amended sod than for sod grown without CMB. Analyses of total nutrients in CMB and in turfgrass and soil indicated that two sod harvests removed all of the CMB sources of N and P incorporated or top-dressed during Tifway bermudagrass establishment and regrowth. Cycling of CMB through sod offers an opportunity for conserving CMB sources of nutrients and benefiting Tifway bermudagrass sod production and properties.

Incorporation or top-dressing of composted biosolids (CB) can enhance turfgrass establishment and sod properties at harvest, but soil phosphorus (P) and nitrogen must be managed to protect water quality. Alum treatment of CB could reduce soluble P concentrations in amended soil and limit runoff loss of P. The objective was to evaluate CB and Alum effects on turfgrass coverage of soil and runoff losses during ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon × C. transvaalensis Burtt-Davey] establishment from sprigs or transplanted sod. Three replications of eight treatments comprised a complete randomized design. Four treatments were composed of ‘Tifway’ sprigged in soil with and without incorporation of CB and Alum. Four remaining treatments were sods harvested from ‘Tifway’ grown with and without top-dressed CB that were transplanted with and without a surface spray of Alum. Surface coverage of ‘Tifway’ sprigged in soil mixed with inorganic fertilizer or CB was comparable to transplanted sod 25 days after planting. In contrast, Alum incorporation acidulated soil, slowed coverage rates of sprigged ‘Tifway’, and increased NH₄-N runoff loss during early establishment in treatments without CB. Incorporation of Alum with CB or inorganic fertilizer in soil before sprigging reduced soil water-extractable P (WEP) more than 38% and reduced runoff loss of soluble reactive P (SRP) in three of four establishment treatments. Although SRP runoff loss from CB-amended sod was greatest among treatments, the Alum spray minimized SRP loss after transplanting. Alum effectively reduced runoff loss of SRP from CB, soil, and turfgrass sources during establishment from sprigs or sod. Additional field research is needed, but incorporated or surface sprays of Alum offer a potential new practice for mitigating runoff loss of SRP from establishing turfgrass.

Compost application to turfgrasses may contribute to accumulation of macronutrients in soil and eventually pose leaching and runoff hazards. The objectives of this study were to determine the influence of compost on soil-dissolved organic C (DOC) and accumulation of NH₄OAc-EDTA-extractable and water-soluble nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) in St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] turf. Dissolved organic C increased from 3 to 29 months after application for unamended and compost-amended soils, indicating contribution from decomposition of both compost and St. Augustinegrass residues. Dissolved organic C was 75%, 78%, and 101% greater 29 months after application of 0, 80, and 160 mg·ha⁻¹ of compost, respectively, than before application. Dissolved organic C and macronutrients exhibited considerable seasonal variation, because DOC and EDTA-extractable P, Ca, Mg, and S increased after compost application, whereas NO₃ declined. Water-soluble K, Ca, and Mg declined, whereas P and S increased from 0 to 29 months. Similar seasonal changes in macronutrient concentrations occurred for unamended and compost-amended soil, indicating that composts, in addition to turfgrass residues, influenced DOC and macronutrient dynamics. Long-term nutrient accumulation occurred in compost-amended turfgrass, but seasonal dynamics were more related to the growth stage of turfgrass than compost. Formation of DOC-cation complexes appeared to contribute to macronutrient mobility, because decreases in DOC and nutrient concentrations occurred during turfgrass dormancy in winter and after high precipitation levels, indicating the potential for leaching of DOC-associated nutrients from soil.

Integrating hydroponic and aquaculture systems (aquaponics) requires balanced pH for plants, fish, and nitrifying bacteria. Nitrification prevents accumulation of fish waste ammonia by converting it to NO₃ ^–-N. The difference in optimum pH for hydroponic cucumber (Cucumis sativa) (5.5 to 6.0) and nitrification (7.5 to 9.0) requires reconciliation to improve systems integration and sustainability. The purpose of this investigation was to: 1) determine the ammonia biofiltration rate of a perlite trickling biofilter/root growth medium in an aquaponic system, 2) predict the relative contribution of nitrifiers and plants to ammonia biofiltration, and 3) establish the reconciling pH for ammonia biofiltration and cucumber yield in recirculating aquaponics. The biofiltration rate of total ammonia nitrogen (TAN) removal was 19, 31, and 80 g·m⁻³·d⁻¹ for aquaponic systems [cucumber, tilapia (Oreochromis niloticus), and nitrifying bacteria (Nitrosomonas sp. + Nitrobacter sp.)] with operating pH at 6.0, 7.0, and 8.0, respectively. With the existing aquaponic design (four plants/20 L perlite biofilter/100 L tank water), the aquaponic biofilter (with plants and nitrifiers) was three times more effective at removing TAN compared with plant uptake alone at pH 6.0. Most probable number of Nitrosomonas sp. bacteria cells sampled from biofilter cores indicated that the aquaculture control (pH 7.0) had a significantly higher (0.01% level) bacteria cell number compared with treatments containing plants in the biofilter (pH 6.0, 7.0, or 8.0). However, the highest TAN removal was with aquaponic production at pH 8.0. Thus, operating pH was more important than nitrifying bacteria population in determining the rate of ammonia biofiltration. Early marketable cucumber fruit yield decreased linearly from 1.5 to 0.7 kg/plant as pH increased from 6.0 to 8.0, but total marketable yield was not different. The reconciling pH for this system was pH 8.0, except during production for early-season cucumber market windows in which pH 7.0 would be recommended.

As the need for landscape and golf course water conservation increases, use of low-quality irrigation water combined with deficit irrigation practices is becoming more common. Information is lacking concerning the effects of water quality on bermudagrass response to deficit irrigation, as well as the extent to which plant growth regulators may ameliorate or delay the negative effects of water stress on warm-season turfgrass. The objectives of this 10-week greenhouse study were to 1) characterize growth, quality, and evapotranspiration (ET) of ‘Tifway’ bermudagrass (Cynodon dactylon × C. traansvalensis Burt Davy) when irrigated at full (1.0 × ET_a) or deficit (0.3 × ET_a) levels of actual turfgrass evapotranspiration (ET_a) using three irrigation water sources [reverse osmosis (RO), sodic potable, and saline] and 2) determine whether application of trinexapac-ethyl (TE) could mitigate turfgrass quality decline under deficit irrigation. Results indicated that turf irrigated with sodic irrigation water exhibited significantly elevated ET_a and shoot growth compared with turf receiving RO or saline irrigation water in both studies. Irrigation water source affected turfgrass quality differently at each irrigation level. TE application improved turfgrass quality and/or delayed firing under soil moisture stress in both studies, with the greatest benefit noted under the less intense conditions of the spring experiment. Elevated canopy temperatures were observed within all deficit irrigation treatments, regardless of water chemistry. Results demonstrate that irrigation water quality may influence turfgrass ET rates. In addition, they suggest that trinexapac-ethyl may offer short-term mitigation of drought stress under deficit irrigation.

Application of organic amendments can increase dissolved organic C (DOC) concentrations, which may influence movement of nutrients and heavy metals in soils. The objectives of this study were to investigate the influence of compost sources and application rates on concentrations of soil DOC, NO₃-N, and extractable P over 29 months after a one-time application of compost to bermudagrass [Cynodon dactylon (L.) Pers.] turf. Few differences were evident between compost sources for soil total organic C (TOC), DOC, and NO₃-N. However, the initial P content of compost sources significantly influenced soil extractable P. Increasing the rate of compost application increased soil TOC initially, but levels remained fairly stable over time. In contrast, DOC continued to increase from 3 to 29 months after application, suggesting that compost mineralization and growth of bermudagrass contributed to DOC dynamics in soil. Dissolved organic C was 98%, 128%, 145%, 175%, and 179% greater 29 months after application of 0, 40, 80, 120, and 160 Mg compost/ha, respectively, than before application. Rate of compost application had less effect on DOC than TOC, as DOC concentrations appeared controlled in part by bermudagrass growth patterns. Soil NO₃-N was generally unaffected by compost application rate, as NO₃-N decreased similarly for unamended soil and all compost treatments. Soil extractable P initially increased after compost application, but increasing the application rate generally did not increase P from 3 to 29 months. Seasonal or cyclical patterns of TOC, DOC, and extractable P were observed, as significantly lower levels of these parameters were observed in dormant stages of bermudagrass growth during cooler months.

Proper water management is a major responsibility of managers of creeping bentgrass grown on putting greens in the hot and humid southern states. The combination of shallow root systems, sand-based root zones, high temperatures, and high evaporative demands frequently results in severe drought stress on bentgrass (Agrostis palustris Huds.) greens. This study was initiated to determine the effects of irrigation frequency on creeping bentgrass turgor pressure and on the O₂ and CO₂ concentrations in a sand-based root zone mixture. In total, 81 plots, 1.5 × 1.5 m each, were established on a USGA-type root zone mixture and organized into 9 groups of 9 plots each. Each group could be irrigated individually. One plot in each group was planted to either `A-4', `Crenshaw', `Mariner', `L-93', or `Penncross' creeping bentgrass. Irrigation frequency treatments of 1-, 2-, and 4-day replacement of historical PET were imposed on three groups each. After establishment, measurements of the leaf water potential, osmotic potential, soil oxygen concentration, and soil carbon dioxide concentrations were made over a 1- to 2-year period. Bentgrass irrigated every 1 or 2 days had significantly (P = 0.05) greater turgor pressures at 0600 hr as compared to turf irrigated every 4 days in 1997. No differences were seen in 1998 due to drier environmental conditions. Concentrations of O₂ and CO₂ in the soil air remained in the optimal range for all treatments, indicating that lack of O₂ in the root zone as a result of frequent irrigation may not be the primary cause for reduced rooting depth of bentgrass grown on highly permeable sand-based root zone mixtures.