Greenhouse studies were conducted at the Univ. of Florida to evaluate the effects of preemergence herbicides on St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] rooting. Metolachlor, atrazine, metolachlor + atrazine, isoxahen, pendimethalin, dithiopyr, and oxadiazon were applied to soil columns followed by placement of St. Augustinegrass sod on the treated soil. Root elongation and biomass were measured following application. Plants treated with dithiopyr and pendimethalin had no measurable root elongation and root biomass was severely (>70%) reduced at the study's conclusion (33 days). Root biomass was unaffected following isoxaben and oxadiazon treatments, but oxadiazon applied at 3.4 kg·ha-1 reduced root length by 50%. Atrazine at 2.2 kg·ha-1 and metolachlor + atrazine at 2.2 + 2.2 kg·ha-1, did not reduce root length in one study, while the remaining atrazine and metolachlor + atrazine treatments reduced cumulative root length and total root biomass 20% to 60%. Metolachlor at 2.2 kg·ha-1 reduced St. Augustinegrass root biomass by >70% in one of two studies. St. Augustinegrass root elongation rate was linear or quadratic in response to all treatments. However, the rate of root elongation was similar to the untreated control for plants treated with isoxaben or oxadiazon. Chemical names used: 6-chloro-N-ethyl-N'-(l-methylethyl)-1,3,5-triazine-2,4-diamine(atrazine);S,S-dimethyl2-(difluoromethyl)-4-(2-methylpropyl)-6-(t∼fluoromethyl)-3,5-pyridinecarbothioate (dithiopyr); N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide (isoxaben); 2-chloro-N-(2-ethyl- 6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin).
Lambert B. McCarty, D. Wayne Porter, Daniel L. Colvin, Donn G. Shilling, and David W. Hall
G.A. Picchioni, C.J. Graham, and A.L. Ulery
Asimina triloba (L.) Dunal is an underused tree species with demonstrated potential as a new fruit crop and landscape ornamental plant. Best management practices for A. triloba are not adequately defined, particularly for field establishment in high-Na conditions characteristic of numerous southern U.S. production areas. We evaluated the growth and net macroelement uptake of field-grown A. triloba seedlings on soil amended with a single addition of gypsum at 0, 7.5, or 15.0 t·ha-1 and later receiving a regular supply of Na-affected but nonsaline irrigation water [sodium adsorption ratio (SAR) of 15.5 and electrical conductivity (EC) at 0.4 dS·m-1]. Over two growing seasons, the soil saturation extract Ca concentration increased while the soil saturation extract SAR decreased with increasing gypsum rate. Amending the soil with gypsum increased total lateral branch extension per tree by 60% to 73% and trunk cross-sectional area (TCSA) per tree by 68% to 87% above a non-gypsum-amended control treatment. Total dry matter accumulation and the net uptake of N, P, and K per tree were over 100% greater following gypsum application as compared to controls. The growth and mineral uptake-enhancing effects of gypsum were likely related to functions of Ca at the root level and on soil physical properties that should be considered in establishing young A. triloba trees with irrigation water containing high sodicity but relatively low total salinity.
Joyce G. Latimer, Reuben B. Beverly, Carol D. Robacker, Orville M. Lindstrom, Ronald D. Oetting, Denise L. Olson, S. Kristine Braman, Paul A. Thomas, John R. Allison, Wojciech Florkowski, John M. Ruter, Jerry T. Walker, Melvin P. Garber, and William G. Hudson
Pesticides have been the primary method of pest control for years, and growers depend on them to control insect and disease-causing pests effectively and economically. However, opportunities for reducing the potential pollution arising from the use of pesticides and fertilizers in environmental horticulture are excellent. Greenhouse, nursery, and sod producers are using many of the scouting and cultural practices recommended for reducing the outbreak potential and severity of disease and insect problems. Growers are receptive to alternatives to conventional pesticides, and many already use biorational insecticides. Future research should focus on increasing the effectiveness and availability of these alternatives. Optimizing growing conditions, and thereby plant health, reduces the susceptibility of plants to many disease and insect pest problems. Impediments to reducing the use of conventional pesticides and fertilizers in the environmental horticulture industry include 1) lack of easily implemented, reliable, and cost-effective alternative pest control methods; 2) inadequate funding for research to develop alternatives; 3) lack of sufficient educational or resource information for users on the availability of alternatives; 4) insufficient funding for educating users on implementing alternatives; 5) lack of economic or regulatory incentive for growers to implement alternatives; and 6) limited consumer acceptance of aesthetic damage to plants. Research and broadly defined educational efforts will help alleviate these impediments to reducing potential pollution by the environmental horticulture industry.
M.D. Richardson and J.W. Boyd
Establishment of zoysiagrass (Zoysia japonica Steud.) from sprigs is often impractical for golf courses and sports fields because of the slow growth rate of the species and subsequent long establishment period. A study was conducted at two different sites in Arkansas to evaluate the effects of soil topdressing and post-plant fertility rates on establishment of zoysiagrass from vegetative sprigs. Each site was planted according to standard methods using freshly-harvested sprigs (18 m3/ha) and either top dressed with 1.0 cm of native soil or maintained without topdressing. Beginning immediately after establishment, N was applied monthly at rates of 0, 1.25, 2.50, 3.75, or 5.0 g·m-2 as urea. Rate of cover was monitored throughout the growing season and elemental analysis of plant tissues was determined 120 days after planting. Topdressing the sprigs with native soil significantly improved establishment compared to traditional sprigging at both sites, presumably because of enhanced sprig survival. Applications of N during the establishment period had little or no overall effect on establishment, although the 0 g·m-2 rate was slightly inferior to all other rates. This study indicates that methods that enhance sprig survival are more important than added fertility for the rapid establishment of zoysiagrass sprigs.
D.M. Glenn and W.V. Welker
Mature peach trees were grown in six different-sized vegetation-free areas (VFA) (0.36 to 13 m2) with and without stage-III drip irrigation for 6 years. As the VFA increased, so did the trunk cross-sectional area, total yield/tree, large fruit yield/tree, and pruning weight/tree. The application of supplemental irrigation increased yield of large fruit and leaf N percentage in all VFAs. Winter hardiness was not affected by either size of the VFA or irrigation. The yield efficiency of total fruit and large fruit decreased, however, with the increasing size of VFAs. The smaller VFAs resulted in smaller, more-efficient trees. Managing the size of the VFA was an effective, low-cost approach to controlling peach tree size and, when combined with irrigated, high-density production, offers a potential for increased productivity.
William V. Welker and D. Michael Glenn
Richard E.C. Layne, Chin S. Tan, David M. Hunter, and Robert A. Cline
Seven high-density (606 trees/ha) management systems for peach [Prunus persica (L.) Batsch cv. Harrow Beauty/Bailey] were compared on Fox sand in southwestern Ontario. Each system had an irrigation component (N = none D = drip, M = microsprinkler) and a fertilizer placement component (B = banded, L= low-rate fertigation, H = high rate fertigation). NB (nonirrigated, banded fertilizer) and DB (drip-irrigated) are commonly used systems in Ontario, while the other five treatment combinations were experimental. Trunk cross-sectional area (TCA) was generally greatest for DH and DB systems, smallest for ML and NB systems, and intermediate for the other three. No symptoms of N or K deficiency or excess were noted for any of the fertilizer treatments. The seven management systems each had similar cumulative yield efficiencies for the first 4 cropping years However, total marketable yields for the 4 years were highest for MB (58.7 t·ha–1), followed in descending order by DB (56.8 t·ha–1), DH (56.6 t·ha–1), MH (53.9 t·ha–1), DL (50.6 t·ha–1), ML (49.8 t·ha–1), and NB (47.5 t·ha–1). Each of the irrigated treatments outyielded the nonirrigated check (NB) and ranged from 4.8% to 23.6%. Only one of the irrigated treatments (MB) outyielded the irrigated check (DB), and by only 3.3%. There was no clear advantage for either the drip or microsprinkler system of irrigation. Banded application of N and K appeared to promote higher yields than by fertigation equivalent to the banded rate, while yields at the low rate of fertigation were lower than for either the high rate of fertigation or the banded application. It appeared that banded fertilizer combined with either microsprinkler (MB) or drip irrigation DB provided the most-effective of the management systems in the first 4 cropping years.
L. Botrini, A. Graifenberg, and M. Lipucci di Paola
The tomato cultivars Edkawi and UC 82B (Lycopersicon esculentum Mill.) were grown hydroponically in a solution [electrical conductivity (EC) 2.4 dS·m-1] containing 150 mm Na (EC 11.4 dS·m-1), 37 mm of K (EC 14.1 dS·m-1), or 75 mm of K (EC 19.7 dS·m-1). The leaf Na content of `Edkawi' and `UC 82B' reached values of 1717 and 2022 mmol·kg-1 dry weight at EC 19.7 dS·m-1, respectively. The high levels of K in the hydroponic solution reduced the Na concentration in the roots, petioles, and stems, but not in the leaves. Potassium concentrations in the petioles of `Edkawi' and `UC 82 B' reached values of 2655 and 2966 mmol·kg-1 dry weight, respectively. At these elevated ECs, the Ca concentrations in the leaves of `Edkawi' and `UC 82B' were 30% and 40% lower than in the control, respectively. The elevated rates of K improved the fruit: flower ratio of `UC 82B', but the high salinity of the solution reduced yields significantly. Plant fresh weight and root dry weight of `UC 82B' were most affected by high EC levels. The elevated levels of K used in this study did not increase yield, but K ions can adjust to Na uptake.
St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is host to the southern chinch bug (SCB) (Blissus insularis Barber). This study evaluated and compared field and laboratory resistance of St. Augustinegrass germplasm to the SCB. Turf field plots of 20 St. Augustinegrass genotypes were monitored monthly for 2 years for damage by the SCB. After each occurrence of damage, plots were treated individually with an insecticide and allowed to become damaged again. Genotypes differed in frequency of damage, which varied from 1.02 occurrences per year for FX-22 and FX-338 to zero occurrences per year for `Floratam'. During the next 2 years when no insecticide was applied, the portion of dead canopy varied from 86% for FX-313 to 0% for `Floratam'. In a second field experiment, SCB damage was evaluated in 10 polyploid St. Augustinegrass genotypes. Damage varied from 90% for `Bitterblue' to 0% for `FX-10'. Oviposition rate was determined from SCB confined in the laboratory on genotypes from both field experiments. Oviposition rate differed among genotypes and predicted (P < 0.01; r 2 = 0.67 to 0.79) field damage. To my knowledge, this paper is the first to report field resistance to the SCB in St. Augustinegrass, validating the use of laboratory bioassays.
D.M. Glenn and W.V. Welker
Abbreviations: BS, bare soil; FRLD, fine-root length density; KS, killed K-31 tall fesuce sod; LRLD, large-root length density; LS, living K-31 tail fescue sod; PT, living Poa trivialis sod. 1 Soil Scientist. 2 Weed Scientist. Mention of a