Cool-season Annuals Research Articles

Performance by Heifers Grazing Sod-Seeded Cool-Season Annuals Seeded on Different Dates Using Two Tillage Intensities

A total of 120 Gelbvieh × Angus crossbred heifers (552 ± 2.5 lb initial BW) grazed pastures of common bermudagrass [Cynodon dactylon (L.) Pers.] overseeded with wheat (Triticum aestivum L.) and annual ryegrass (Lolium multiflorum Lam.) for a 3-year study to compare the effect of seeding dates and tillage intensities on heifer growth performance. Half of the pastures were seeded in early September (Early) and half in mid October (Late). Within seeding date, half of the pastures were disked once (1×) and half were disked twice (2×) before seeding. Grazing began when forage mass reached approximately 2000 lb/acre and continued through 11 May 2002 (year 1), 25 April 2003 (year 2), and 10 May 2004 (year 3). Forage mass was greater from Early than from Late seeded pastures for 2 of the first 3 months of grazing resulting in 17-day earlier grazing initiation and approximately 165 lb less hay fed per heifer. Total body weight gain, or gain while grazing cool-season annuals did not differ between seeding dates or tillage intensities. Producers in the Mid South region with bermudagrass pastures may have considerable flexibility in their decisions as to when to seed annual forages and to what intensity they till their sod depending upon how soon they need available forage.

Response of Landscape-grown Warm- and Cool-season Annuals to Nitrogen Fertilization at Five Rates

Current nitrogen (N) fertilizer recommendations for landscape-grown ornamentals are based on limited research. The objective of this research was to evaluate plant response of selected warm- and cool-season annuals to N fertilizer applied at five rates in the landscape. Three warm-season annual species [‘Profusion Cherry’ zinnia (Zinnia elegans ×angustifolia), ‘Cora White’ vinca (Catharanthus roseus), and ‘Golden Globe’ melampodium (Melampodium divaricatum)] and three cool-season annual species [‘Telstar Crimson’ dianthus (Dianthus chinensis), ‘Delta Pure Violet’ pansy (Viola wittrockiana), and ‘Montego Yellow’ snapdragon (Antirrhinum majus)] were transplanted into raised beds containing subsoil fill in U.S. Department of Agriculture (USDA) hardiness zone 9a. Slow-release N fertilizer was applied over an 18-week period at an annual N rate of 0, 2, 4, 6, and 12 lb/1000 ft2. Trials were replicated a second year. Plant size index (SI), tissue chlorophyll (SPAD), and plant quality were determined every 6 weeks. Shoot biomass and tissue total Kjeldahl N (TKN) were determined at 18 weeks. Regression analysis indicated that all species required N inputs at annual rates exceeding 8 lb/1000 ft2 to achieve maximum size, shoot biomass, or SPAD. However, acceptable quality plants were produced at much lower N rates. We suggest application of N fertilizer at a rate of 4 to 6 lb/1000 ft2 per year to landscape-grown annuals to maintain acceptable plant quality and growth. We expect fertilization at lower rates (based on aesthetics) can reduce the amount of fertilizer applied and the potential for nutrient losses in runoff or leachate. Future research should address N fertilization needs in higher fertility soils as well as the response of other plant species.

Differences in water use efficiency among annual forages used by the dairy industry under optimum and deficit irrigation

The increasing cost and scarcity of water for irrigation is placing pressure on Australian dairy farmers to utilize water more efficiently, and as result, water use efficiency (WUE) of forages is becoming an important criterion for sustainable dairy production. This study was conducted to identify more water use efficient forage species than the dominant dairy forage, perennial ryegrass (Lolium perenne L.). Seventeen annual forage species were investigated under optimum irrigation (I1) and two deficit irrigation treatments (nominally 66 and 33% of irrigation water applied to the optimal level), over 3 years at Camden, NSW, on a brown Dermsol in a warm temperate climate. Forages with the highest yield generally had the highest WUEt (total yield/evapotranspiration). Under optimal irrigation, there was a three-fold difference in mean annual WUEt between forages, with maize (Zea mays L.) having the highest (42.9 kg ha−1 mm−1) and cowpea (Vigna unguiculata (L.) Walp.) the lowest (13.5 kg ha−1 mm−1), with 11 of the forage species having a greater WUEt than perennial ryegrass. The ‘harvested’ forages maize, wheat, triticale (Triticosecale rimpaui Wittm.) and maple pea (Pisum sativium L.) generally had higher mean WUEt (26.7–42.9 kg ha−1 mm−1) than the remaining forages which were defoliated multiple times to simulate grazing (13.5–30.1 kg ha−1 mm−1). The reduction in annual WUEt in response to deficit irrigation was greatest for the warm season forages with up to 30% reduction for maize, while most of the cool season annuals were not significantly affected by deficit irrigation at the levels imposed. In order to maximize WUEt of any forage, it is necessary to maximize yield, as there is a strong positive relationship between yield and WUEt. However, while WUEt is an important criterion for choosing dairy forages, it is only one factor in a complex system. Choice of forages must be considered on a whole farm basis and include consideration of yield, nutritive value, cost of production and risk.

Differences in yield among annual forages used by the dairy industry under optimal and deficit irrigation

While perennial forages dominate the feed base on Australian dairy farms, poor persistence of perennial ryegrass (Lolium perenne L.) and relatively poor forage nutritive value of kikuyu (Pennisetum clandestinum Hochst. ex. Chiov.) and paspalum (Paspalum dilatatum Poir.) has led to an increasing interest in growing annual forages. Thus, this study was conducted to identify annual forage species that are more productive than the commonly used perennial pasture species. Seventeen annual forages were investigated under ‘optimal’ irrigation and two deficit irrigation treatments (nominally 66 and 33% of irrigation water applied of the optimal level) over 3 years at Camden, New South Wales, on a brown dermosol in a warm temperate climate. The forages evaluated were: Italian ryegrass (Lolium multiflorum Lam.), oats (Avena sativa L.), triticale (Triticosecale rimpaui Wittm), wheat (Triticum aestivum L.), balansa clover (Trifolium michelianum Savi), berseem clover (Trifolium alexandrinum L.), maple pea (Pisum sativum L.), Persian clover (Trifolium resupinatum L. var. majus Boiss.), subterranean clover (Trifolium subterraneum L.), forage rape (Brassica napus L.), forage radish (Raphanus sativus L.), maize (Zea mays L.), Japanese millet [Echinochloa esculenta (A. Braun) H. Scholz], pearl millet [Cenchrus americanus (L.) Morrone], sorghum [Sorghum bicolor (L.) Moench], cow pea [Vigna unguiculata (L.) Walp.] and lablab [Lablab purpureus (L.) Sweet]. There was more than a 4-fold range in annual yield between forages, but the length of the growing season and season of growth made direct comparisons difficult. Under optimal irrigation, maize produced the highest mean yield of 29.0 t DM/ha in only 125 days, which was over three times greater than cow pea (9.2 t DM/ha) grown in the same season yet requiring 190 days. Of the cool season annuals, wheat had the highest mean yield of up to 20.6 t DM/ha in 230 days, which was more than three times the yield of the lowest yielding forage, subterranean clover, at only 6.5 t DM/ha in 215 days. The forages which require harvesting generally had higher yields within a growing period of similar length than those that were defoliated to reflect being ‘grazed’. Combining annual forages in an annual cycle (e.g. maize and wheat) had the potential to produce up to 47 t DM/ha. Deficit irrigation reduced annual yield of all warm season-grown forages ranging from 8% for sorghum up to 48% for maize. In contrast, annual yield reductions were generally smaller for cool season forages, there being no reduction for forage rape, subterranean clover or oats, but up to 35% for Persian clover. However, while yield is an important criterion for choosing dairy forages, it is only one factor in a complex system, and choice of forages must be considered on a whole-farm basis and include water use efficiency, nutritive value, cost of production and risk.

Fall and Winter Management Affect Spring Growth and Nutritive Value of Tifton 85 Bermudagrass

Spring regrowth of ‘Tifton 85’ bermudagrass (Cynodon spp.) has been slow or stands have appeared weakened in some years in North Florida following overseeding with cool-season annuals. This 2-year experiment compared effects of (i) different bermudagrass sod management practices in fall and (ii) winter/spring grazing management of overseeded cool-season forages on subsequent spring and early-summer productivity of Tifton 85 bermudagrass. For overseeded pastures, postgraze stubble height of cool-season forages during winter/spring did not affect bermudagrass production in spring/early summer. Early-season bermudagrass yield generally was greater for pastures not overseeded the previous fall than those that were overseeded with cool-season forages; however, bermudagrass yields by July were as great or greater in plots that had been overseeded compared to unseeded controls. In plots that were not overseeded, leaving an 8-inch bermudagrass stubble entering winter resulted in greater early-season bermudagrass yields the following year than leaving a 2-inch stubble. The results of this study suggest that early-season growth of Tifton 85 bermudagrass may be reduced either by overseeding cool-season forages or by leaving insufficient bermudagrass residue in fall. There were, however, no long-term negative effects on bermudagrass stands of any of the management options tested.

Animal performance and economic comparison of novel and toxic endophyte tall fescues to cool-season annuals1

Increased costs of annual establishment of small grain pasture associated with fuel, machinery, and labor are eroding the profitability of stocker cattle enterprises. Interest has therefore increased in development of cool-season perennial grasses that are persistent and high quality. This study occurred on 24 ha (divided into thirty 0.81-ha paddocks) located at the University of Arkansas Division of Agriculture Livestock and Forestry Branch Station, near Batesville. Two tall fescue (Festuca arundinacea Schreb.) cultivars infected with novel endophytes (NE), Jesup infected with AR542 endophyte (Jesup AR542), and HiMag infected with Number 11 endophyte (HM11) were established in September 2002. Jesup AR542 and HM11 were compared with endemic endophyte Kentucky 31 (KY-31) tall fescue; wheat (Triticum aestivum L.) and cereal rye (WR, Secale cereale L.) planted in September 2003, 2004, and 2005; and annual ryegrass [RG, Lolium perenne L. ssp. multiflorum (Lam.) Husnot] planted in September 2004 and 2005. Each year, 3 steers (3.7 steers/ha) were placed on each pasture for fall and winter grazing, and 5 steers (6.2 steers/ha) were placed on each pasture for spring grazing. Animal performance is presented by year in the presence of a year x treatment interaction (P < 0.01). Body weight gain per hectare of steers grazing NE tall fescue was greater (P < 0.01) than those of KY-31 and WR during 2003 to 2004, whereas in 2004 to 2005, BW gain per hectare of steers grazing NE and RG did not differ (P < or = 0.29) and was greater (P < 0.01) than that of WR, which was greater (P < 0.01) than that of KY-31. During 2005 to 2006, BW gain per hectare was greater (P < 0.01) for steers grazing RG than those of NE and WR, which did not differ (P > or = 0.14). Body weight gain per hectare was least (P < 0.01) for steers grazing KY-31. Average net return of NE tall fescue was greater (P < 0.01) than KY-31, but profitability of NE did not consistently differ from cool-season annuals. Across the 3-yr study, NE tall fescue produced net returns per hectare of $219; this level of profitability would require 4 yr for a new planting of NE tall fescue to break even. Novel endophyte tall fescues offer potential benefits related to decreased risk of stand establishment of annual forage crops, longer growing season, and acceptable animal performance.

Effect of species of cool-season annual grass interseeded into Bermudagrass sod on the performance of growing calves1

Two experiments were conducted to evaluate the effect of species of cool-season annual grass on the growth of stocker cattle over 3 yr. In Exp. 1, the small grains (SG) oat (O), rye (R), and wheat (W), or combinations of SG and annual ryegrass (RG), were interseeded into Bermudagrass sod in a completely randomized design with a 3 x 2 factorial arrangement of treatments. In Exp. 2, RG was planted alone or with O, R, triticale (T), or W in a completely randomized design. Pastures were planted in late October of each year, and seeding rates were 134.4 and 22.4 kg/ha for SG and RG, respectively. In Exp. 1, grazing was initiated on December 18. In Exp. 2, grazing was initiated on December 23 for SG pastures and January 21 or February 16 for RG pastures in yr 1 and on December 8 for all pastures in yr 2. Grazing was managed using the put-and-take method, in which additional calves were added as needed to maintain equal grazing pressure among pastures. In Exp. 1, no interactions (P > or = 0.28) were detected, so the main effects of SG species and RG addition are discussed. From December 18 to March 12, there were no differences in ADG (P > or = 0.17), whereas during the spring (from March 12 to May 7), addition of RG increased (P = 0.05) ADG. Using RG increased (P < or = 0.01) animal grazing-days/hectare and BW gain/hectare. Wheat tended (P = 0.08) to increase BW gain/hectare compared with the other SG, and O tended (P = 0.09) to produce less BW gain/hectare than the other SG. The treatment x year interaction was significant (P < or = 0.05) in Exp. 2. In yr 1, no differences (P = 0.25) were observed for ADG from December 23 to March 8, but during the spring grazing period (from March 8 to May 5), ADG of calves grazing TRG was less (P < or = 0.04) than that of those grazing RG, RRG, or WRG. The RRG combination produced more (P < or = 0.03) BW gain/hectare than ORG, RG, or TRG and tended (P = 0.06) to produce more BW gain/hectare than WRG. The WRG combination produced more (P < or = 0.05) BW gain/hectare than TRG and RG, and ORG tended (P = 0.09) to produce more BW gain/hectare than RG alone. Pastures planted to R or W produced more (P < or = 0.05) BW gain/hectare than RG alone or T. During yr 2, there were no differences (P > or = 0.44) in ADG, BW gain/hectare, or grazing-days/hectare. In conclusion, the choice of cool-season annual to establish is highly weather-dependent, but R and W are generally superior to other small grains, and RG is a necessary complement to SG when interseeding cool-season annuals into Bermudagrass sod.

Soil Nutrient Dynamics from Swine Effluent Application to Common Bermudagrass Overseeded with Cool-Season Annuals

ABSTRACT A 3-year study was conducted to investigate the major nutrient dynamics in soil receiving swine effluent as the sole source of plant nutrients for warm-season perennial bermudagrass and cool-season annuals. Berseem and crimson clovers, ryegrass, and wheat were seeded in common bermudagrass for a year-round nutrient uptake and spring through summer haying. Bermudagrass dry matter of 9.0 mg ha−1 (3-yr average) was not impacted by the overseeding treatments. Most of the soil nutrient element concentrations increased during the study, particularly phosphorus in top 5 cm of the soil surface. The increase of Fe and NO3-N concentration at the 0-5 cm depth was high. Double cropping can be a better practice than growing bermudagrass alone, but, the effluent nutrient application must be coordinated with the nutrient requirements of the growing forages in order to minimize the build up of any nutrient in the soil.

Responsible Plant Growth Recommendations from Greenhouse-grown Bedding Plant Experiments Must Integrate Data from Postharvest Landscape Evaluations

Multiple experiments conducted over the past 5 years suggest that greenhouse-grown bedding plants, particularly fall-propagated cool-season annuals, may exhibit reductions in vegetative growth and flowering in response to plant growth regulators (PGRs) applied at rates commonly used by growers. Studies using Viola ×wittrockiana Gams as a model system indicated that paclobutrazol applied at production stages and rates reportedly used by growers could result in significant postharvest residual responses that adversely impacted landscape performance. Most of these rates were also included within the recommended ranges on the agricultural chemical labels. Multiple applications to the same plants during production increased the severity of the residual responses and decreased the rates at which residual responses were detectable in landscape plantings. Tests with additional taxa, Brassica oleracea L. var. acephala DC, Calendula officinalis L., Ipomoea carnea Jacq. subsp. fistulosa (Mart. ex Choisy) D. Austin, Lantana urticoides Hayek `L.S. Red', Lupinus texensis Hook., Plumbago auriculata Lam., Salvia greggii Gray, and Verbena canadensis Kunth `Homestead Purple', PGR formulations and at various times of the year indicate that the postharvest landscape responses to PGRs vary among taxa and seasons. These results strongly suggest that in order for researchers to make responsible recommendations on PGR use, studies must include not only greenhouse or nursery production data, but also subsequent testing for residual responses to the PGRs in landscape settings.

Performance of Stocker Cattle Grazing Cool-Season Annual Grass Mixtures in Northern Arkansas

Over 3yr, cool-season annual grasses, including oats (Avena sativa L), cereal rye (Secale cereale L; CR), annual ryegrass (Lolium multiflorum Lam.; RG), and soft-red winter wheat (Triticum aestivum L) or the combinations of CR and RG (RRG); wheat and CR (WR); wheat and RG (WRG); or wheat, CR, and RG (WRRG) were planted in twenty-four 0.81-ha pastures on the University of Arkansas Livestock and Forestry Branch Station near Batesville to evaluate the effect of species of cool-season annual grass on the growth of stocker calves. Grazing was initiated on January 6, October 23, and October 30 in Year 1, 2, and 3, respectively. Summarized across year, animal performance during the fall and winter was not affected (P=0.20) by combination of cool-season annual grass, averaging 1.16 kg/d. Across year, the greatest ADG during the spring was observed for stocker calves on the RG, RRG, wheat, and WRG treatments, which did not differ (P>0.10). The spring ADG of stocker calves on the RRG treatment was 19% greater (P<0.02) than that of stocker calves on oats, CR, WR, and WRRG. Across year, gain per hectare was not different (P>0.10) for calves on the RRG, RG, WRG, and wheat treatments; calves on RRG had greater (P= 0.05) gain per hectare than calves on WRRG. Addition of RG to CR or wheat yielded the greatest in ADG and gain per hectare in 2 of the 3yr and when averaged across year. If this enterprise were used for custom grazing and pasture were charged at $35/45.4kg of BW gain, profit per hectare would be best for RG, RRG, wheat, and WRG (averaging $305.29, $313.64, $305.86, and $295.93/ha, respectively).

Development of Replacement Heifers Using Programmed Feeding

This experiment was conducted to determine the effects of diet and pattern of gain on reproductive performance. On November 24, 80 spring-born Angus- and Brangus-sired heifers (BW = 230 ± 23 kg) were allotted by breed and BW to one of four treatments (two replicates per treatment). Heifers were program-fed to gain 0.68 kg/d until April 14 (134 d, MODERATE ), grazed wheat (cv. Hickory, Triticum aestivum L.) and ryegrass (cv. Marshall, Lolium multiflorum Lam.) interseeded into bermudagrass pasture ( GRAZED ), or were program-fed to gain 0.23 kg/d until February 4 (71 d) and then program-fed to gain 0.91 kg/ d (63 d, SLOW-FAST ) or grazed wheat and ryegrass pastures ( SLOW-GRAZED ). On February 4, MODERATE heifers were heavier (P 0.70) among treatments. Pregnancy rate tended to be less (P=0.16), conception date was later (P SUN ) tended to be greater (P=0.14) for GRAZED and SLOW-GRAZED heifers than for MODERATE and SLOW-FAST heifers. Program feeding can be a valuable tool for developing replacement heifers as long as BW goals pre-breeding are reached. Grazing heifers on cool-season annuals during breeding may impair reproduction as a result of the high forage N concentrations, causing reduced fertility.

A Guide to Overseeding Warm-Season Perennial Grasses with Cool-Season Annuals

A Guide to Overseeding Warm-Season Perennial Grasses with Cool-Season Annuals

A Guide to Overseeding Warm‐Season Perennial Grasses with Cool‐Season Annuals

Overseeding warm-season perennial grasses with cool-season annuals in the southeastern U.S. has many benefits. Because the growing seasons overlap in autumn, management practices to reduce the warm-season grass competition are necessary for early cool-season forage production. Cool-season forage production and distribution is dependent on species, seeding rates, and planting methods. Growing seasons also overlap in spring which delays spring recovery of the warm-season grass.

Spring Forage Yield and Nutritive Value of Texas Black Medic Accessions

Black medic (Medicago lupulina L.) has become naturalized in south‐central USA where, in semiarid climates, it acts as a cool‐season annual. Cultivation for wildlife and livestock forage and seed has not been fully realized as cultivars adapted to warm and dry climates have not been developed. This study evaluated forage yields and nutritive value of black medic accessions collected in Texas. March, April, and May forage yield, acid detergent fiber (ADF), acid detergent lignin (ADL), N, and P concentrations of 11 black medic accessions collected in Texas were compared with cultivar George at Stephenville, TX, during establishment and first self‐reseeding years. Entries exhibited no frost damage and insignificant insect damage, but some Texas accessions were more vigorous in February and flowered earlier than other Texas accessions and George. Some Texas accessions were also more productive (P &lt; 0.01) than others as well as George. Forage yields among entries ranged from 0.6 to 1.5 Mg ha−1 yr−1 when averaged over years and harvest months. Harvest month affected all entry yields equally and peaked at 2.3 Mg forage ha−1 yr−1 during May of the first season but declined in the second, self‐reseeding year despite greater rainfall. March ADF, ADL, N, and P concentrations tended to be lower than those of later harvests while the higher‐yielding accessions also tended to have greater ADF and ADL concentrations. The results indicate that forage yield and nutritive value of naturalized black medic germplasm from Texas is variable and that a blend from the southern Great Plains should be developed.

Spring Forage Yield and Nutritive Value of Texas Black Medic Accessions

Black medic (Medicago lupulina L.) has become naturalized in south-central USA where, in semiarid climates, it acts as a cool-season annual. Cultivation for wildlife and livestock forage and seed has not been fully realized as cultivars adapted to warm and dry climates have not been developed. This study evaluated forage yields and nutritive value of black medic accessions collected in Texas. March, April, and May forage yield, acid detergent fiber (ADF), acid detergent lignin (ADL), N, and P concentrations of 11 black medic accessions collected in Texas were compared with cultivar George at Stephenville, TX, during establishment and first self-reseeding years. Entries exhibited no frost damage and insignificant insect damage, but some Texas accessions were more vigorous in February and flowered earlier than other Texas accessions and George. Some Texas accessions were also more productive (P < 0.01) than others as well as George. Forage yields among entries ranged from 0.6 to 1.5 Mg ha−1 yr−1 when averaged over years and harvest months. Harvest month affected all entry yields equally and peaked at 2.3 Mg forage ha−1 yr−1 during May of the first season but declined in the second, self-reseeding year despite greater rainfall. March ADF, ADL, N, and P concentrations tended to be lower than those of later harvests while the higher-yielding accessions also tended to have greater ADF and ADL concentrations. The results indicate that forage yield and nutritive value of naturalized black medic germplasm from Texas is variable and that a blend from the southern Great Plains should be developed.

Competition and Survival of Perennial Cool-Season Grass Forages Seeded with Winter Wheat in the Southern Great Plains

ABSTRACT Domestic wheat is the standard winter and spring forage of the Southern Great Plains forage-livestock production system; however, cool-season perennial forage grasses can also become an integral component of this grazing system for livestock producers. Typically, following a mid-September sowing date, only 30–40 growing days are available for cool-season grass establishment. As a consequence, a one year growing season, without livestock grazing pressures, is necessary to provide good stand establishment of the perennial cool-season species. The opposite is true for the case where cool-season annuals like winter wheat or rye can be grazed fairly heavily following a period of stand establishment. The inability of a livestock producer to heavily graze a newly sown perennial cool-season grass forage pasture provides not only a loss of land resources for grazing, but limits the sites where a cattleman can sow pasture to cool-season species and continue to graze his livestock. This study was conducted to determine if perennial cool-season grass forages could compete and become established when inter-seeded with winter wheat as a companion species. Stand counts were performed on each three replicate plots of eighty-two perennial cool-season cultivars and experimental germplasms to determine stand establishment and seedling survival rates. Depending on the species, stand counts of plants per m2 obtained in the fall of 2001 ranged from 0, with no survival, to a value of 40, which indicates a 100%, fully established stand. Results from this study indicate that crested wheatgrass, tall wheatgrass, intermediate wheatgrass, smooth bromegrass and western wheatgrass, when inter-seeded and under competition with winter wheat, can be successfully established and provide grazing resources for livestock producers in the Southern Plains during the first year of sowing.

Herbicides for Desiccating Dallisgrass (Paspalum dilatatum)–Bermudagrass (Cynodon dactylon) Pasture Sod Prior to Overseeding with Annual Ryegrass, (Lolium multiflorum)1

Autumn desiccation of warm-season perennial grasses is one method to enhance the establishment and early production of overseeded cool-season annuals. Potential herbicides were compared with paraquat, glyphosate, and dalapon to desiccate a dallisgrass–bermudagrass sod for overseeding annual ryegrass over a 2-yr period. Fluazifop-P at ≥ 0.14 kg/ha, glufosinate at ≥ 1.12 kg/ha, and haloxyfop at ≥ 0.07 kg/ha provided good dallisgrass desiccation and ryegrass yields similar to those with dalapon and glyphosate. Dallisgrass recovery was inversely related to desiccation rating for all treatments except for paraquat. None of the herbicide treatments had the desired combination of acceptable dallisgrass desiccation, improved early ryegrass production, and acceptable dallisgrass recovery.Nomenclature: Dalapon; fluazifop-P; glufosinate; glyphosate; haloxyfop; paraquat; sethoxydim; annual ryegrass, Lolium multiflorum Lam. ‘Gulf’; bermudagrass, Cynodon dactylon (L.). Pers.; dallisgrass, Paspalum dilatatum Poir.Additional index words: Desiccant, overseeding.

267 Phytotoxic Effect of Pine Bark Mulch in Landscape Beds

The use of shredded bark, wood chips, and other organic mulches to conserve water and moderate soil temperatures is a common practice in landscape maintenance. Four mulch materials (cottonseed hulls, cypress pulp, pine bark, and pine straw) were examined to determine effects on plant growth and soil conditions in annual flower beds during a 1-year rotation of warm season to cool season annuals. Inhibited plant growth was observed in pine bark treatments at the conclusion of the growing season for both plantings. Effects on soil conditions were insignificant over the year-long study in pine bark treatments. To further investigate potential phytotoxic effects of pine bark and other mulch used in the initial study, a seed bioassay was performed to determine the influence of mulch extracts in solution on germination and primary root elongation.

Steer Performance and Nutritive Values for Continuously and Rotationally Stocked Bermudagrass Sod-Seeded with Wheat and Ryegrass

Considerable research has been conducted comparing animal and plant responses between rotational and continuous stocking, but more studies are needed to evaluate intensive, multi-paddock rotational stocking for managing forages in the southeastern USA. A 2-yr study was conducted with bermudagrass [Cynodon dactylon (L.) Pers.] pastures that were drill-planted with wheat (Triticum aestivum L.) and ryegrass (Lolium multiflorum Lam.) to compare steer performance and forage nutritive values between continuous stocking, 3-paddock low-intensity and 11-paddock high-intensity rotational stocking systems for both the cool-season annuals and warm-season perennial. In vitro dry matter digestibility (IVDMD) and crude protein (CP) were similar (P > 0.10) between continuous stocking and averages of pregraze, midgraze, and postgraze sample times for both rotation systems. There were decreases (P 0.10) by the grazing treatments in either season. Higher stocking rates were achieved (P 0.10) during the warm season. Thus, there was higher (P 0.10) during the warm season. Results of the study indicate that rotational stocking can enhance steer liveweight gain per acre because of increased stocking rate on wheat-ryegrass, but not on bermudagrass. Also, the more intensive 11-paddock system was not more productive than the 3-paddock system in either season.

Patterns of Growth and Soil-water Utilization in some Exotic Annuals and Native Perennial Bunchgrasses of California

In western California, exotic cool-season annuals appear to have widely replaced native perennial bunchgrasses as the herbaceous community dominants in grasslands, oak savannas, and oak woodlands. We argue that because these two herbaceous plant types possess very different life histories, this invasion may have correspondingly altered seasonal patterns of soil-water availability. To begin to assess this hypothesis, in this study we compared exotic cool-season annuals and native perennial bunchgrasses in terms of growth, biomass allocation, rooting distribution, root morphology, and soil-water utilization. Exotic cool-season annuals completed their life cycle early in the dry season through rapid growth apparently made possible by a high proportional allocation to shoots in combination with the efficient production of roots of high specific root length. Further, annuals tended to concentrate root growth and soil-water utilization in the upper soil profile. In contrast, native perennial bunchgrasses allocated a high proportion of their biomass to the production of a deep root system, which allowed them to continue soil-water utilization well into the dry season and contribute to the formation of a very dry soil profile. Taken together, these contrasting patterns suggest that the invasion of exotic cool-season annuals might have produced a corresponding increase in the amount of water present at depth in the soil profile during the dry season.