Weed Encroachment Research Articles

Apomictic Bahiagrass Expressing the bar Gene Is Highly Resistant to Glufosinate under Field Conditions

Bahiagrass (Paspalum notatum Flugge) is one of the most important low‐input turf and forage grasses in the southeastern USA and in other subtropical regions. Its open growth habit, however, facilitates weed encroachment and its low tolerance to commercially available herbicides complicates weed management. Genetic transformation protocols were recently developed for bahiagrass that allow now, among other approaches, the introduction of herbicide resistance genes. Integration of the bar gene expression cassette into the genomic DNA of the apomictic bahiagrass cultivar Argentine was confirmed by Southern blot analysis. Stable expression of the bar gene was detected by an immunochromatographic assay in primary transgenic lines and the seed‐derived progeny plants. Several independent transgenic lines showed no growth inhibition, chlorosis, or necrosis following a spray application of 1.0% glufosinate ammonium [2‐amino‐4‐(hydroxymethylphosphinyl)butanoic acid] under greenhouse conditions. The selected transgenic plants did not differ morphologically from wild‐type plants and produced viable seeds in the greenhouse and field. All weeds that coestablished during the field experiment, as well as wild‐type bahiagrass, displayed full leaf necrosis after application of 0.3% glufosinate ammonium. Transgenic bahiagrass plants were resistant to a field application of 0.6% glufosinate ammonium, which is twice the recommended rate for weed control, without any symptoms of phytotoxicity.

HERBICIDE USE ON GOLF COURSE NATIVE AREAS CONTAINING WEEPING LOVEGRASS

Weeping lovegrass (Eragrostis curvula) is commonly used in native areas bordering golf courses in the Southeastern United States. These areas do not receive significant levels of maintenance, thus weed encroachment is a problem that can negatively impact the functional and aesthetic values of the golf course. The objectives of this study is to determine which selective postemergent herbicides labeled for use on golf courses can remove weeds from Weeping Lovegrass and to determine the level of phytotoxicity. Herbicides included monosodium methane arsenate (MSMA 6.0) applied at 3.0 lb/acre a.i., sulfosulfuron (Certainty) at 0.047 lb/acre a.i., metribuzin (Sencor 75 DF) at 0.5 lb/acre a.i., and imazaquin (Image 70 DG) at a rate of 0.5 lb/acre a.i.. Treatments were applied on July 20, 2004 to 9.6 × 9.6 plots arranged in a randomized complete block design (RCBD) using Teejet 8005 nozzles at 40 psi calibrated to deliver 40 ga/acre. Plots were monitored daily and data was collected 0, 7, 14, 21, 28, 35, and 42 DAT. Sulfosulfuron and MSMA provided the highest level of weed control 35 DAT. Metribuzin and imazaquin provided limited weed suppression compared to the control. Initial phytotoxic damage to the Lovegrass was observed in all herbicide treatments. The highest level of phytotoxic damage was observed in the MSMA and Metribuzin treatments; however there was no apparent damage at 42 DAT. Herbicide applications of sulfosulfuron and MSMA are effective in reducing weed populations with acceptable levels of phytotoxicity to the Lovegrass.

THE INFLUENCE OF MINIMUM TILLAGE SYSTEMS UPON THE SOIL PROPERTIES, YIELD AND ENERGY EFFICIENCY IN SOME ARABLE CROPS

The paper presents the influence of the conventional ploughing tillage technology in comparison with the minimum tillage, upon the soil properties, weed control, yield and energy efficiency in the case of maize (Zea mays L.), soyabean (Glycine hispida L.) and winter wheat (Triticum aestivum L.) in a three years crop rotation. For all cultures within the crop rotation, the weed encroachment is maximum for the disc harrow and rotary harrow soil tillage, followed by the chisel and paraplow. The weed encroachment is minimum for the conventional ploughing tillage technology. The results of investigations showed that the yield is a conclusion soil tillage systems influence on soil properties, plant density assurance and on weed control.

New Options for Annual Bluegrass Control in Overseeded Bermudagrass Putting Greens

Annual bluegrass (Poa annua L.) continues to be a problem in bermudagrass golf greens overseeded with roughstalk bluegrass (Poa trivialis L. `Sabre) due to weed encroachment from adjacent fairways, lack of selective herbicide options, and weed diversity. A 2-year study was conducted on an overseeded `Tifgreen bermudagrass putting green to evaluate effects of herbicide treatments on overseeding and annual bluegrass control. Excellent annual bluegrass control (≥90%) and acceptable turfgrass cover (§70%) was achieved with oxadiazon at 2.2 kg·ha-1 a.i. applied 60 days before overseeding (DBO). Fenarimol (AS) at 4.1 kg·ha-1 a.i. (30 + 15 DBO) followed by 1.4 kg·ha-1 a.i. 60 days after overseeding (DAO) and dithiopyr at 0.6 kg·ha-1 a.i. (60 DBO + 120 DAO) also provided acceptable results. Dithiopyr at 0.4 kg·ha-1 a.i. (30 DBO + 120 DAO), dithiopyr at 0.3 kg·ha-1 a.i. (30 DBO + 30 + 120 DAO), and fenarimol (G) at 2.0 kg·ha-1 a.i. (45 + 30 DBO) followed by 0.8 kg·ha-1 a.i. 60 DAO provided inconsistent annual bluegrass control (55% to 75% in 1999 and 87% to 95% in 2000), but offered acceptable turfgrass cover (§70%) each year. The remaining treatments were generally ineffective and provided <50% annual bluegrass control one or both years. Oxadiazon applied 60 DBO at 2.2 kg·ha-1 a.i. provides an excellent option for annual bluegrass control in overseeded bermudagrass putting greens.

Use of field margins by foraging yellowhammers Emberiza citrinella

Some agri-environment schemes promote the creation and management of a variety of non-crop habitats on farmland in the UK, yet there has been relatively little monitoring to assess how species, particularly birds, use these habitats. The present study deals with a declining UK farmland bird species, yellowhammer Emberiza citrinella, and considers to what extent grass margins of arable fields are used as a foraging habitat when feeding nestlings. Studies were carried out in lowland mixed farmland in southern England. Grass margins and other non-crop field boundary habitats, such as hedgerows and ditches, were selected relative to cropped areas by yellowhammers. No significant difference was found between use of cut and uncut grass margins. Studies have shown that grass margins support high densities of invertebrates and their provision at the edge of arable fields would benefit yellowhammers during the breeding season both as habitat for prey and as nesting habitat. During the breeding season from May to August, management should create cut and uncut grass margins in close proximity to each other. This could be achieved by cutting only the outer edge of the grass margin, maintaining cover next to the hedgerow. Cut areas would provide easier access to food resources for birds and prevent weed encroachment to the crop, whilst adjacent uncut areas would maintain invertebrate sources and provide nesting cover for yellowhammers.

Physical sod suppression as an alternative to herbicide use in pasture renovation with clovers

Using herbicides for sod suppression during pasture renovation by legume sod-seeding often results in the loss of potentially usable forage, weed encroachment, and inadequate legume:grass ratios. Physical sod suppression methods could alleviate some of the problems associated with suppression via herbicide. A study was conducted in Québec, Canada, to investigate, as an alternative to herbicide, sod suppression by sheep grazing or mowing before and after spring no-till seeding of red clover (Trifolium pratense L.) or white clover (T. repens L.). Sod-suppression treatments included six physical suppression methods: mowing or sheep grazing, to 5 or 10 cm, at seeding and when the grass sward reached 30 cm during the first 2 mo of clover establishment, or similarly managed mowing or sheep grazing to 5 cm with an additional defoliation the previous fall. Additional treatments included suppression by herbicide (glyphosate [N-(Phosphonomethyl) glycine] at 2.6 kg a.i. ha–1) and two controls: sod-seeding with no sod suppression and no seeding. Among the physical suppression treatments, grazing and mowing to 5 cm resulted in highest clover densities, similar to those achieved via herbicide suppression. Red and white clover had similar plant densities. Yield components and total forage yields varied with sites. Clover yields tended to be higher with herbicide than under physical suppression treatments. However, increasing the severity of physical suppression increased clover yields. Weed encroachment was observed only with herbicide sod suppression. Unlike suppression with herbicide, physical suppression did not decrease total forage yields in the renovation and post-renovation years when compared with controls. Forage quality was increased in the renovation year by both physical suppression methods and herbicide when compared with unrenovated controls; but the increase was greater with herbicide suppression. Only the most severe of the physical suppression methods sustained increased forage quality in the year after renovation. Timely mowing or grazing as methods for suppression of grass sod during renovation with legumes appear to have potential, but cannot yet be recommended as alternatives to herbicide. Key words: Clover, forage, grazing, pasture renovation, sod-seeding

Response of Incomplete Tifton 9 Bahiagrass Stands to Renovation

Establishment of warm-season grasses from seed is often impeded by slow germination and emergence, and low seedling vigor. Stand development can be further retarded by unfavorable soil moisture resulting from high temperatures and erratic precipitation. Management of poorly established stands of warmseason grasses has received limited research attention. Two- or 3year old, poorly established stands (basal occupation 0.05) than the control. Bahiagrass stands with at least a few plants per m 2 should be managed to minimize weed encroachment, but introducing additional seed, with or without tillage, offered no benefit.

Response of incomplete Tifton 9 bahiagrass stands to renovation

Establishment of warm-season grasses from seed is often impeded by slow germination and emergence, and low seedling vigor. Stand development can be further retarded by unfavorable soil moisture resulting from high temperatures and erratic precipitation. Management of poorly established stands of warm-season grasses has received limited research attention. Two- or 3-year old, poorly established stands (basal occupation < 61%) of ‘Tifton 9’ bahiagrass (Paspalum notatum Flügge var. saure) at a dry upland site and at a moist lowland site were reseeded (5.6 kgh a-1) in April of 2 different years either without tillage or after rototilling or light disking and compared to a non-seeded control. Our objective was to determine whether any combination of tillage and/or seeding would enhance stand coverage. At the upland site, basal occupation of the control increased from an initial 61 to 80%. No benefit was derived from interseeding, and both tillage treatments resulted in a stand reduction (P < 0.05) after 1 year. At the lowland site, basal occupation increased froman initial 28 to 59% for the control. Similar responses were observed with renovation treatments, but none were greater (P >0.05) than the control. Bahiagrass stands with at least a few plants per m2 should be managed to minimize weed encroachment, but introducing additional seed, with or without tillage, offered no benefit.

Effects of growth-stage-based alfalfa harvest on weed encroachment and resultant quality

Growth-stage-based alfalfa harvest treatments were imposed on a 2-yr-old Beaver alfalfa stand in 1992 to determine the effect of harvest treatments on yield and quality. By 1993, alfalfa cut at the vegetative stage or prebud stage contained 25% dandelions by weight. At these stages weeds lowered crude protein content in the total forage relative to pure alfalfa. Weed contents were similar and less than 1% by weight in forage cut at prebloom and later stages. Crude protein and fibre contents were similar in total forage and pure alfalfa at prebloom and later stages. Key words: Acid detergent fibre, crude protein, cutting management, dandelion, growth stage, neutral detergent fibre

Biology and Management of Dollar Spot (Sclerotinia homoeocarpa); an Important Disease of Turfgrass

Turfgrasses have been utilized by humans for >10 centuries to enhance their environment, but the modern turfgrass industry developed primarily during the past three decades, largely in response to increased population growth and urbanization. Turfgrass culture represents an important economic component of horticulture in North America with annual expenditures of $25 to $45 billion in the United States between 1982 and 1993 (Beard and Green, 1994; Gibeault and Cockerham, 1985). In return, turfgrass provides numerous benefits, including functional (e.g., reduction of soil erosion, pollution, and noise), recreational (e.g., provision of recreational surfaces for improved health and safety), and aesthetic benefits (e.g., improved aesthetic value and community pride) (Beard and Green, 1994; Gordon et al., 1996). Because of these economic and environmental benefits, turfgrass and turfgrass health have become increasingly important. Dollar spot (Sclerotinia homoeocarpa F.T. Bennett) is one of the most important diseases that affect turfgrass; it can cause considerable damage, particularly to highly maintained golf course putting greens, closely mown fairways, and bowling greens (Goodman and Burpee, 1991). This disease can also damage less intensively managed turfgrass grown on home lawns, recreational and athletic facilities, and educational or industrial properties. Dollar spot reduces the aesthetic and playing quality of infected turf, and can contribute to weed encroachment and plant death (Fig. 1) (Smith et al., 1989). Dollar spot is a widespread disease that affects many turfgrass species throughout North America, Central America, Australia, New Zealand, Japan, the British Isles, and continental Europe (Couch, 1995; Fenstermacher, 1980; Vargas, 1994). Except for western Canada and the Pacific northwest region of the United States, dollar spot is the most common disease of turf in North America (Couch, 1995). The persistent nature of this disease in turfgrass swards often requires intensive control measures. As a result, more money is spent to manage dollar spot than to control any other turfgrass disease on golf courses (Goodman and Burpee, 1991).

Lantana camara L. invasions in dry rainforest ‐ open forest ecotones: The role of disturbances associated with fire and cattle grazing

Abstract A field experiment was used to evaluate the effects of fire and cattle grazing on the initiation of Lantana camara invasions in dry rainforest‐open forest ecotones in the gorges of the Macleay River, NSW. A factorial combination of four factors (burning, biomass removal, soil scarification, and fertilization) at two levels (presence and absence) was established to assess the suitability of disturbed patches for germination, survival, and growth in association with changes in microclimate and resource availability. Burning, biomass removal and soil scarification, either singularly or in any combination, significantly increased germination, on average, by 19%, from 50.2% to 59.7%. Survival increased on average 26% across all treatments while mortality decreased by 26% when compared with the control. The differences between treatment combinations were not significant. Seedling growth was significantly enhanced by all disturbances, except by soil scarification alone. Treatment combinations that reduced vegetation cover (burning and/or biomass removal) and, therefore reduced shading, significantly increased L. camara biomass production by an average of 140% for all treatments. The control yielded 14.0 g m−2, while fertilizer alone and biomass removal alone yielded 27.6 g m−2 and 40.5 g m−2, respectively. Other treatment combinations averaged 35.2 g m−2 and were not significantly different from each other. Consequently, successful invasions are likely to occur whenever canopy disturbances create patches of greatly decreased competition and/or increased resource availability. Shading plays a greater role as a limiting factor than any other, while surface soil macronutrient levels are also important, particularly when combined with canopy disturbances that increase light availability. The effects of biomass reduction and soil disturbance associated with fire and cattle grazing are significant in the successful invasion of L. camara. Management strategies to reduce weed encroachment and community degradation must identify and maintain ecological barriers to L. camara invasion in order to promote rainforest conservation and biodiversity.

Weed Encroachment in Established Alfalfa as Affected by Cutting Frequency

Grazing-tolerant alfalfa (Medicago sativa L.) cultivars are more persistent than hay-type cultivars under severe grazing pressure but the influence of defoliation on weed encroachment is not well defined. Our objective was to determine the effect of rest interval between cuttings on encroachment of large crabgrass [Digitaria sanguinalis (L.) Scop.] or common bermudagrass [Cynodon dactylon (L.) Pers.] into a grazing-tolerant alfalfa cultivar. We used small-plot field experiments witb four replications of 'Alfagraze' alfalfa to evaluate nine treatment combinations of (i) harvesting at 2-, 4-, and 6-wk intervals, and (ii) overseeding with common bermudagrass, large crabgrass, or nothing. Experiments were conducted for 3 yr at Eatonton, GA, on Davidson loam (clayey, kaolinitic, thermic, Humic Paleudult) and at Athens, GA, on Cecil sandy clay loam (clayey, thermic, kaolinitic, Typic Hapudult). Alfalfa yields were similar at both locations when harvested at 4- or 6-wk intervals. Grass invasion was virtually nil with the 4- and 6-wk treatments at Eatonton but at Athens there was some grass encroachment, probably a result of soil compaction,which adversely affected overall alfalfa growth. Cutting at 2-wk intervals reduced alfalfa yields to 50% of the 4- or 6-wk cut treatments and resulted in heavy bermudagrass encroachment during the third year. Alfalfa cut every 4 or 6 wk persisted well but stands were reduced when cut every 2 wk. Results suggest that frequent defoliation will not only reduce alfalfa yield but also favors grass encroachment. Thus, defoliation methods that keep alfalfa canopies at a high level would appear to be desirable in resisting bermudagrass and crabgrass invasion and increasing yield of grazed alfalfa.

Weed Management and Tall Fescue Quality as Influenced by Mowing, Nitrogen, and Herbicides

A 3‐yr field study was conducted to determine the influence of N level (98 and 196 kg ha−1 yr−1), mowing height (3.2,5.5, and 8.8 cm), and three herbicides on weed encroachment and overall quality of tall fescue Festuca arundinacea Schreb. cv. Rebel II. The major objective of this study was to identify cultural methods of excluding weed development in tall fescue. Dithiopyr [3,5‐pyridinedicarbothioic acid, 2‐(difluoromethyl)‐4‐(2‐metbylpropyl)‐6‐(trifluoromethyl)‐S,S‐dimethylester] and pendimethalin [N‐(l‐ethylpropyl)‐3, 4‐dimethyl‐2,6‐dinitrobenzenamine] were applied preemergence for smooth crabgrass [Digitaria ischaemum (Schreber) Schreber ex Muhlenb.] control, and fenoxaprop [(±)‐2‐[4‐[(6‐chloro‐2‐benzoxazolyl)oxy]‐ phenoxylpropanoic acid] was applied postemergence for crabgrass control. Rates of dithiopyr and pendimethalin were reduced or eliminated on selected plots in the last 2 yr of the study to determine if reduced herbicide inputs would continue to provide effective crabgrass control. Tall fescue mowed at 8.8 cm resisted smooth crabgrass invasion, exhibited best visual summer turf quality in 1990 and 1991, had poorest winter turf quality, and had highest white clover (Trifotium repens L.) populations. Other environmental factors and lower mowing height (3.2 or 5.5 cm) reduced summer turf quality in 1990 and 1991. High N improved fall and winter turf quality, but not summer quality. Nonherbicide‐treated plots receiving high N had less smooth crabgrass than low N plots, but high N provided no additional crabgrass reduction in herbicide‐treated plots. High mowing (8.8 cm) was the best cultural management strategy for reducing smooth crabgrass encroachment and maintaining tall fescue cover. Results indicated that smooth crabgrass control with label use rates of herbicides was warranted when mowing tall fescue at 3.2 or 5.5 cm.

The Effect of Farmyard Manure Anaerobic Treatment on Weed Seed Viability

ABSTRACT Weed encroachment is a serious problem of contemporary agriculture. Farmyard manure and other organic fertilizers can be major sources of weed seeds that get into the soil. One of the methods for eliminating weed seed germination is the technology of anaerobic treatment of the farmyard manure with a simultaneous production of biogas, the so called “Olomouc method”. Before anaerobic fermentation seeds of all 11 species under study (i.e. Tripleurospermum maritimum, Echinochloa crus-galli, Plantago major, Chenopodium album, Chenopodium strictum, Thlaspi arvense, Avena fatua, Rumex obtusifolius, Amaranthus retroflexus, Agropyron repens and Polygonum lapathifolium) manifested a high germination power. The seeds positioned in the lower layers of the fermentation unit (1,800 mm) lost their germination power after one month's treatment. In the sub-surface layers (400 mm) of the farmyard manure there was only a small proportion of viable seeds belonging to 4 species. The germination rate of Echinochloa crus-galli, Chenopodium album, Rumex obtusifolius and Amaranthus retroflexus was 36%, 9%, 19% and 4%, respectively.

Buffalograss Tolerance to Postemergence Herbicides

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a turfgrass species traditionally adapted to low-rainfall areas that may incur unacceptable weed encroachment when grown in higher rainfall areas such as Florida. An experiment was performed to evaluate the tolerance of two new buffalograss cultivars, `Oasis' and `Prairie', to postemergence herbicides commonly used for grass, broadleaf, and sedge weed control. Twenty to 40 days were required for each cultivar to recover from treatment with asulam, MSMA, and sethoxydim (2.24, 2.24, and 0.56 kg-ha-l, respectively). Other herbicides used for postemergence grass weed control (metsulfuron, quinclorac, and diclofop at 0.017, 0.56, and 1.12 kg·ha-1, respectively) did not cause unacceptable buffalograss injury. Herbicides used for postemergence broadleaf weed control, triclopyr, 2,4-D, sulfometuron, dicamba (0.56, 1.12, 0.017, and 0.56 kg·ha-1, respectively), and a three-way combination of 2,4-D + dicamba + mecoprop (1.2 + 0.54 + 0.13 kg·ha-1), caused 20 to 30 days of unacceptable or marginally acceptable turfgrass quality, while 20 days were required for `Prairie' buffalograss to recover from atrazine treatments. `Oasis' buffalograss did not fully recover from 2,4-D or 2,4-D + dicamba + mecoprop through 40 days after treatment. Herbicides used for postemergence sedge control, bentazon and imazaquin, caused slightly reduced, but acceptable, levels of turf quality in both cultivars throughout the experiment. Chemical names used: 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine (atrazine); methyl[(4-aminophenyl)sulfonyl]carhamate (asulam); 3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (bentazon); 3,6-dichloro-2-methoxybenzoic acid (dicamba); (±)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid (diclofop); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid (imazaquin); (±)-2-(4-chloro-2-methylphenoxy)propanoic acid (mecoprop); 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]benzoic acid (metsulfuron); monosodium salt of methylarsonic acid (MSMA); 2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one(sethoxydim); 2-[[[[(4,6-dimethylethyl-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid (sulfometuron); [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid (triclopyr); (2,4-dichlorophenoxyl)acetic acid (2,4-D); 3,7-dichloro-8-quinolinecarboxylic acid (quinclorac).

No-till establishment of perennial, warm-season grasses for biomass production

Herbaceous biomass crops have the potential to capture solar radiation and store energy as a renewable fuel resource. Establishment procedures that can be used successfully without damage to the environment are essential. The objective of this research was to develop procedures to establish perennial, warm-season grasses, such as switchgrass ( Panicum virgatum L.) and lovegrass ( Eragrostis curvula L.), without tillage and preparation of a fine seedbed. Two applications of paraquat spaced 3 weeks apart or a single application of glyphosate can be used to suppress sod before no-till plantings. Carbofuran applied in the row at 1.1 kg ha −1 with the seed increased seedling vigor and populations. Application of 1.1 kg ha −1 of atrazine when seedlings began to emerge provided post-planting weed suppression. Weed encroachment occurring in years after establishment was halted by 2 kg ha −1 of simazine applied before first growth in the spring. These data provide guidelines for successful establishment of herbaceous perennial, warm-season grass biomass crops.

Yield and Regrowth Characteristics of Alfalfa Grazed with Sheep. II. Summer Grazing1

AbstractGrazing alfalfa (Medicago sativa L.) in summer would provide high quality forage during periods of low rainfall when other forages are in short supply. ‘Arc’ alfalfa, grown on fine‐loamy, mixed, mesic Fluventic Dystrochrept at Blacksburg, VA, was grazed by sheep following two hay cuts in 1982 and 1983 with six treatments: (i) no grazing with hay being cut at 1/10 bloom; (ii), (iii), and (iv) grazing began approximately 14 days after second hay cut and continued for 2, 4, and 6 weeks, respectively; (v) grazing began at early bud stage and continued for 10 days in 1982 and 7 days in 1983; and (vi) grazing began at early bloom and continued for 7 days. Following grazing, hay was cut on each treatment if regrowth reached 1/10 bloom stage before killing frost. No grazing was imposed in 1984 and hay was harvested three times from plots from all six treatments. Forage remaining after grazing for 2, 4, or 6 weeks was higher in percent leaf, in vitro dry matter digestibility, crude protein, Ca, Mg, and P concentration, and was lower in cell wall constituents than after grazing at early bud or bloom. Grazing for 4 and 6 weeks precluded fall hay harvest and increased weeds. Alfalfa yield in 1984 was reduced by grazing except grazing at early bloom. Yield was 8.5, 7.3, 7.1, 6.7, 7.3, and 8.7 Mg ha−1 for the six treatments, respectively. Weed encroachment generally increased with increased grazing duration (GD). Grazing could decrease productivity, especially as GD is lengthened, but may be less detrimental than previously supposed.

Comparison of Conventional and Mulching Mowers for Kentucky Bluegrass Maintenance

Abstract The effects on Kentucky bluegrass (Poa pratensis L.) turf quality of mowing with either a mulching mower or a conventional rotary mower, having clippings re moved or returned, were determined. Turf that received 0, 150, or 300 kg N ha–1 yr–1 was mowed at 5 cm either biweekly, weekly, or twice weekly. Turf quality, weed encroachment, and thatch buildup were monitored. Highest quality was found where turf was mowed twice weekly with a conventional rotary mower with clippings returned and received 300 kg N ha–1 yr–1. Quality ratings for turf mowed with the mulching mower were equal to or significantly lower than ratings for turf mowed with a conventional rotary mower with clippings returned on 13 of the 17 rating dates. Thatch buildup and weed encroachment responded to N level, with more thatch and fewer weeds at the highest N level.

Genetic and Environmental Determinants of Zoysiagrass Adaptation in a Subtropical Region1

Abstract Visual evaluations of a 5-year-old replicated planting of 63 zoysiagrass (Zoysia spp.) genotypes in southern Florida showed highly significant (P < 1%) differences in overall vigor and survival, flight selections and 2 commercial cultivars (‘Emerald’ and ‘Meyer’) were sodded at 2 distant sites. Selected genotypes (FZ-28, FZ-80, FZ-26, and FL-1753) were significantly better adapted, had significantly less weed encroachment and greater vigor and ground coverage, than Emerald or Meyer. The latter commercial cultivars were unacceptable in most evaluations. Furthermore, FZ-28 and FZ-80 had low sting nematode (Belonolaimus longicaudatus Rau) counts and FZ-28 had few eggs of Banks grass mite (Oligonychus pratensis [Banks]). Sod webworm (Crambus spp.) infestation appeared to be another variable closely associated with adaptive differences among genotypes and explained serious establishment problems at some sites. Zoysiagrass was successfully established as a turf only on one site involving fumigated soil and generally proved poorly suited for this subtropical region.

Fertilization Effects on Yield and N Concentration of Midland Bermudagrass1

AbstractA high yielding summer forage grass capable of with standing high temperatures and low moisture is needed in the northeastern U. S. ‘Midland’ bermudagrass( Cynodon dactylon (L.) Pers.) would meet these requirements, but production and management methods for the northeast need to be investigated.Studies were conducted over 3 years at two locations in West Virginia to determine the effects of N and K rates on yields and N recovery of ‘Midland’ bermudagrass. Treatments consisted of factorial combinations of zero, 112, 224, and 448 kg of N and K/ha. Herbage was harvested two or three times at both locations each year, depending on the growing season. Herbage yield and N concentration of the herbage increased and percent recovery of the applied N decreased as N application rates increased. Oven‐dried forage yields reached 19,000 kg/ha when N was applied at 448 kg/ha. Yield, N concentration of forage, and percent N recovery varied in response to K application with K having little overall effect. Weed encroachment was enhanced by N application at one location, but not at the other location. Temperatures as low as −29 C were recorded with no apparent winter killing.Soil pH decreased slightly with N application at one location, but not at the other. Available soil K correlated positively with K application rates and negatively with N application rates. Available soil Mg at both locations and available Ca at one location were decreased as N rates increased. Available soil Mg was decreased when K was applied at the zero N level, but otherwise, it was unaffected by K application.These studies indicate that while N is necessary for maximizing herbage yield of ‘Midland’ bermudagrass, other factors such as location and soil type are important in determining persistence and longevity. Also, additional nutrients, such as Mg, need to be considered as N levels are increased.