P. Mislevy

Growth of Subtropical Forage Grasses under Extended Photoperiod during Short-Daylength Months

onstrated under field conditions that short daylengths induce decreased growth, then the possibility exists for One constraint on cattle production in the southeastern USA is increasing grass productivity during the cool, shortthe low productivity of perennial forage grasses during the shortdaylength months. Evidence indicates that total growth during these daylength months by genetic selection and development months could be enhanced by exposing these grasses to extended of photoperiod-insensitive cultivars. photoperiod. A detailed analysis of their year-round productivity and Studies in controlled environments showed that grass nutritive value is needed to understand fully the consequences of growth is sensitive to photoperiod length (Hay, 1990; overcoming the photoperiod-induced decline in growth. A 2-yr experiMarousky et al., 1991, 1992). In addition, sensitivity to ment was established at Ona, FL, in which photoperiod was extended photoperiod can have a large influence on the relative to 15 h throughout the short-daylength months. Four grasses were growth of grasses under natural conditions. Four grasses studied: ‘Pensacola’ bahiagrass, Paspalum notatum Flugge var. Saurde Parodi; ‘Tifton 85’ bermudagrass, Cynodon spp. L. Pers.; ‘Florakirk’ (Pensacola bahiagrass, Tifton 85 bermudagrass, Flobermudagrass; and ‘Florona’ stargrass, Cynodon nlemfuensis Vanderrakirk bermudagrass, and Florona stargrass) grown unyst var. nlemfuensis. Growth increases were observed in all grasses der field conditions had overall increases in forage yield during the short-daylength months as a result of the extended-photoduring the short-daylength months when plots were period treatment, with increases in the January through March hartreated with 15-h photoperiods (Sinclair et al., 2001). vests of 3-fold or more for Pensacola bahiagrass and 1.5to 2.5-fold In the 2-yr study, overall winter forage yield was signififor Tifton 85 bermudagrass. Generally, there was no evidence of cantly increased by the extended photoperiod in all adverse consequences from sustained growth during the short-daycases except for one season for Florona stargrass. Pensalength months either in the subsequent spring and summer growth or in traits measured in below-ground tissue. With one exception, cola bahiagrass and Tifton 85 bermudagrass had yield there was no major influence of the sustained growth on forage nutriincreases as a result of the extended photoperiod of 1.8tive value during the short-daylength months for any of the yearfold and greater. round harvests. Pensacola bahiagrass had decreased crude protein An objective of this paper was to extend the analysis under the extended-photoperiod treatment relative to the naturalof the results of overall yield (Sinclair et al., 2001) to a daylength treatment. Overall, these results indicated that the selection detailed examination of the year-round seasonal variaand genetic incorporation of photoperiod insensitivity into these grasses tion in forage yield in response to an extended-photopecould enhance productivity without adverse consequences. riod treatment. In particular, attention was given to the hypothesis that stimulated growth of these grasses during the cool-season, short-daylength months might reC production in the southeastern USA is limsult in depressed forage production in the subsequent ited to a large extent by low forage production spring and summer. Therefore, data are presented here during short-daylength months. The decrease in forage on year-round forage yield from harvests at 4or 5-wk production can be quite dramatic in these months. For example, in Florida the growth of Paspalum and Cynointervals throughout a 2-yr experiment. In addition, bedon species during October through March was relow-ground plant samples were obtained to examine the ported to account for only 14 and 27% of the annual hypothesis that possible decreases in forage production yield, respectively (Mislevy and Everett, 1981). The dein the spring and summer following growth stimulated crease in growth occurs in spite of the fact that there by extended daylengths might result from decreased appears to be adequate soil moisture, soil fertility, and partitioning of the materials to the below-ground tissues. sufficiently high temperatures to allow substantially Therefore, data are reported on mass, nitrogen congreater yields (Sinclair et al., 1997). The cause of decentration, and carbohydrate concentration of belowcreased grass growth may be a response to the short ground tissue. daylengths during these months. If it can be clearly demA second objective of the study was to determine if there was a change in nutritive value of the forage T. Sinclair and L. Premazzi, USDA-ARS, University of Florida, PO produced by sustained grass growth as a result of exBox 110965, Gainesville, FL 32611-0965 USA; J. Ray, USDA-ARS, tended photoperiod during the short-daylength months. Crop Genetics and Production, P.O. Box 345, Stoneville, MS 38776 Several types of data were collected to examine nutritive USA; P. Mislevy, University of Florida, IFAS, Range Cattle Research value, including leafiness, crude protein (CP) concentraand Education Center, 3401 Experiment Station, Ona, FL 338659706 USA. Mention of a trademark or proprietary product does not tion, and in vitro digestible organic matter (IVDOM) constitute a guarantee or warranty of the product by the U.S. Departconcentration. ment of Agriculture and does not imply approval or the exclusion of other products that may also be suitable. Received 17 Apr. 2002. *Corresponding author (trsincl@mail.ifas.ufl.edu). Abbreviations: CP, crude protein; IVDOM, in vitro digestible organic matter; TNC, total nonstructural carbohydrates. Published in Crop Sci. 43:618–623 (2003).

Agronomic characteristics of US 72-1153 energycane for biomass

Abstract Biomass production and plant quality vary between plant species and morphological components of a plant. The purpose of this two-part experiment was (1) to study the influence of energycane [ Saccharum sp. (L.) ‘US 72-1153’] harvest treatments (6) on dry biomass yield and (2) monitor changes in quantity and quality of plant components with increased plant height. Treatments for Part 1 determined the influence of plant height when harvested at 1.2, 2.5, and 3.7 m, mature stage in October (4.9 m, in flower), mature stage in December (4.9 m, in flower), and additional treatment harvested in October, which received half the total N (168 kg ha −1 ) on dry biomass yield from 1986 to 1989. Part 2 treatments were to monitor changes in quantity and quality (crude protein and in vitro organic matter digestion) of plant components (green leaf, dead leaf, and stem) at 0.6 m plant height increments to a final height of 4.3 m during 1986 and 1987. Treatments from both parts of the study received 25 kg P ha −1 and 93 kg K ha −1 in one application and 336 kg N ha −1 yr −1 in single or split applications applied prior to growth of each harvest. Plants repeatedly harvested at the 1.2 m height (Part 1) and mature stage produced a 4-year average yield of 10 and 48 Mg ha −1 yr −1 dry biomass, respectively and decreased in dry biomass yield 89% (1.2 m harvest) and 53% (mature harvest) between years 1 and 4. The stem (1986 and 1987) and dead leaf (1986) plant components increased quadratically as plant height increased, and green leaf decreased from 70% (0.6 m) to 17% (4.3 m height). The crude protein concentration decreased 51% (green leaf) and 81% (stem) and in-vitro organic matter digestion decreased 54, 32, and 34% for dead leaf, green leaf, and stem, respectively as plant height increased from 0.6 to 4.3 m. These data indicate that harvest management is an important factor for energycane biomass yield, ratoon-crop success and plant quality if biomass is used as a methane source.

Harvest management effects on quantity and quality of Erianthus plant morphological components

Lignocellulose materials can be readily produced under tropical and subtropical conditions and converted to a variety of fuels through bioconversion methods. However, biomass production and plant quality may differ between plant species and morphological components of plants. The objectives of these two experiments were to: (1) determine the influence of plant height at harvest on Erianthus arundinaceum (Retz) Jesw-IK76-110 dry biomass (DB) yield; and (2) monitor changes in tiller density, quantity and quality of plant components with increased plant height. Experiment (1) determined the influence of plant height when harvested at 1.2, 2.5 and 3.7 m, mature stage in October (4.9 m), mature stage in December (4.9 m, plus inflorescence), and an additional treatment harvested in October, which received half the total N (168 kg ha−1) annually on DB yield from 1987 to 1990. Experiment (2) treatments were to monitor changes in quantity and crude protein (CP) and in vitro organic matter digestion (IVOMD, estimate of soluble cell solids) of green leaf, dead leaf and stem plant components, leaf area index and tiller number at 0.6 m plant height increments to a final height of 4.3 m during 1987 and 1988. Treatments from both experiments of the study received 25 kg P and 93 kg K ha−1 in one application add 336 kg N ha−1 y−1 in single or split applications applied annually prior to regrowth of each harvest. Plants repeatedly harvested at the 1.2 m height and mature stage in December (Experiment (1)) produced a 4-y average yield of 5.2 and 51.5 Mg ha−1 y−1 DB, respectively. These same two treatments had a yield reduction of 100% (plants died) and 1% between years 1 and 4. Leaf area index increased quadratically to a maximum of 17 at the 3.1 m plant height treatment. Percentage green leaf, total tillers and live tillers decreased quadratically, while dead leaf and dead tillers increased linearly and stem increased quadratically as plant height was delayed from 0.6 to 4.3 m. Crude protein and IVOMD of green leaf and stem decreased quadratically with plant maturity. Knowing the quantity and quality of plant components at various physiological stages can be important to biomass producers, who need to make logical field decisions regarding biomass feedstock that should be utilized immediately after a freeze or stockpiled for later use.

West Indian Dropseed/Giant Smutgrass (Sporobolus indicus var. pyramidalis) Control in Bahiagrass (Paspalum notatum) Pastures1

Abstract: Field experiments were conducted in 1997 and 1998 to evaluate the effect of mowing followed by hexazinone for West Indian dropseed/giant smutgrass (Sporobolus indicus var. pyramidalis) (hereafter referred to as dropseed) control. The experimental design was a split plot, with mowing (nonmowed [mature] and 35-cm regrowth) as the whole plot and hexazinone rate (0.0 [control], 0.56, 0.84, 1.12, 1.40, and 1.68 kg ai/ha) as the subplot treatments. The application of 0.84 kg/ha hexazinone provided 94 and 81% dropseed control, 365 d after treatment (DAT) during 1997 and 1998, respectively. Increasing application rate to 1.12 kg/ha hexazinone provided 87 and 88% dropseed control, 365 DAT during 1997 and 1998, respectively. Both the 0.84 and 1.12 kg/ha rates provided the same average control (87.5%); however, the 1.12 kg/ha rate provided consistent control over years. Mowing dropseed, followed by hexazinone application at 35-cm regrowth, provided no additional control when compared with no mowing treatments. Rates of hexazinone at 1.40 and 1.68 kg/ha caused phytotoxicity to bahiagrass and increased bare soil surface area, especially 90 and 120 DAT. Phytotoxic effect on bahiagrass and on bare soil decreased 365 DAT, resulting in 75 to 80% total forage cover. Concentration and yield of total nonstructural carbohydrates were significantly lower for the mowed 35-cm regrowth treatment than for the nonmowed plants; however, even in its weakened condition this reduction had no effect on dropseed control. Nomenclature: Hexazinone; West Indian dropseed/giant smutgrass, Sporobolus indicus (L.) R. Br. var. pyramidalis (P. Beauv.) Veldkamp; S. indicus (L.) R. Br. var. indicus #3 SPZIN; S. jacquemontii Kunth.; S. poiretii (Roem. & Schult.) A. S. Hitchc. # SPZIN; bahiagrass, Paspalum notatum Fluegge # PASNO. Additional index words: Bermudagrass, CYNDA, Cynodon dactylon (L) Pers., hexazinone, pasture weeds, tropical forage. Abbreviations: DAT, days after treatment; GC, percent ground cover; TNC, total nonstructural carbohydrates.

Soybean response to gibberellic acid treatments

Early-maturing soybean lines (Glycine max (L.) Merr.) grown in subtropical areas during short days can produce economic seed yields. However, the plants are short, and many of the pods are produced close to the soil, making commercial harvest difficult. The feasibility of increasing the lengths of the first three internodes by growth regulator application was evaluated at two locations over a 3-year period using separate plots of Amsoy 71 (Maturity Group (MG) II) and Williams (MG III) soybean by spraying each cultivar with 0, 25, or 50 g (a.i.) ha−1 of gibberellic acid (GA) in 280 L ha−1 water when the hypocotyl was cracking the soil. The 25 g ha−1 treatment increased (p<.05) the length of the hypocotyl and first internode 60% and 25% in 1979 and 36% and 17%, respectively, in 1980. Increasing the GA application to 50 g ha−1 had no additional effect on hypocotyl elongation, but the length of the first internode continued to increase linearly. Gibberellic acid treatment did not stimulate elongation of internodes above the first two, and internodes above the fifth tended to be shorter, causing total plant height at maturity to be the same as untreated plants. The overall effect of GA application at cracking time on harvestable seed yield was about nil, since GA decreased yields by 8–11%, but it increased stem elongation, so a greater portion of seeds were produced above 80 mm that were accessible to commercial combining. The application of GA generally did not affect (p<.05) seed quality. Seed weight was reduced significantly at both locations in 1979 but not in 1980. These data indicate that elongation of the lower stem portion of early-maturing soybean cultivars grown in subtropical areas during short days can be increased significantly by GA to improve commercial harvesting, but the treatments appear to have little net effect on seed yield.

Effect of fertilizer and nematicide treatments on crops grown for biomass.

Abstract Successful production of biomass for energy requires selection of species with high annual yields and development of proper management conditions. Pennisetum purpureum, Erianthus arundinaceum, Sorghum bicolar, and Tripsacum dactyloides were grown as single biomass crops and Brassica campestris, Sorghum bicolor were grown in sequence under one nematicide and two fertilization treatments. The experiment was conducted over a three year period. P. purpureum (52·2 Mg ha−1) and Erianthus (46·4 Mg ha−1) produced highest dry biomass yield when recommended fertilizer rate for forage production was applied and the plants were cut once each year. Harvesting P. purpureum twice each year reduced yields 65% compared with the single cut. Decreasing fertilizer by one-half lowered yield 14–26% for P. purpureum and sorghums; 49% for T. dactyloides (zero fertilizer applied), whereas Erianthus increased from 46·4 to 54·0 Mg ha−1 with the lower fertility. The application of 6·7 kg ha−1 active nematicide on the soil surface in late March of each year did not control nematodes nor affect yields. Biomass yields from P. purpureum and Erianthus when grown on flatwood soils in peninsular Florida at the normal fertilizer rate and harvested once per year were higher than yields at reduced fertilizer treatments. Additional research is needed to determine optimum fertilizer levels for each grass grown under specific soil conditions.

Harvesting operations and energetics of tall grasses for biomass energy production: A case study

Abstract The U.S.A. imports about 50% of its energy needs while Florida imports about 85%. Among the renewable energy sources available, biomass appears promising especially in the southeast which includes Florida because of a favorable environment for production and the available methods to convert biomass to energy. Optimal production of biomass requires the identification and management of high yielding persistent perennial cultivars. Elephantgrass ( Pennisetum purpureum Schum.) and energycane ( Saccharum spontaneum L.) are two tall grasses that meet these requirements. To optimize the supply of convertible biomass, suitable methods of harvesting the crop must be available. The purpose of this research was to study the feasibility and energetics of harvesting, drying, and baling tall grasses with conventional farm machinery. A Mathews rotary scythe and a New Holland 849 Auto Wrap large round baler were determined to provide a practical harvesting system for baled biomass averaging 15–27 Mg ha −1 . The rotary scythe can be used for harvesting and fluffing or turning a windrow over to expedite drying. This harvesting system requires about 3 kg diesel fuel Mg −1 dry biomass (DB), 25 min of time Mg −1 DB, and a cost of about

Co-combustion of waste, biomass and natural gas

10 to 12 Mg −1 DB. Energy requirements of harvesting operations would be about 300–375 MJ Mg −1 DB, and primary energy requirements for production and harvesting are about 1100–1500 MJ Mg −1 DB. For each unit of fossil fuel invested in the total production and harvesting system, 12–15 units would be returned in biomass.

Mineral concentrations in four tropical forages as affected by increasing daylength. II. Microminerals

Abstract The University of Florida-Sunland Training Center-Clean Combustion Technology Laboratory is engaged in a program of research, development and demonstration on co-combustion of non-hazardous waste (NHW) with cellulosic biomass (CB) and natural gas (NG) using a restored two-stage incinerator. The objective is to develop waste-to-energy systems technologies leading to the greater use of NHW and CB, two renewable sources of energy. Various types of CB are considered including ‘dirty wood chips’ from forest residues, utility line clearing operations, tree surgeon residues, Christmas trees, pine cones, and cultivated energy crops such as leucaena, eucalyptus, napiergrass, energy cane, and agricultural residues. This work, which reports on the initial exploratory experiments, points to systems arranged to coburn NHW, CB and NG which can provide environmentally safe solid-waste disposal and economical sources of steam energy.

Selection in Setaria sphacelata for winter survival

Pure stands of the Florakirk and Tifton 85 bermudagrass [Cynodon dactylon (L) Pers.], Florona stargrass (Cynodon nlemfuensis Vanderyst), and Pensacola bahiagrass (Paspalum notatum Fluegge) were established in central Florida during the summer of 1997. Individual grass plots were exposed to an artificial light, which extended the daylength. There were two daylength treatments, extended (artificial light used to maintain daylength at 15 h) and normal daylength conducted over a two-year period. Samples were harvested at distances of 4.0 m ‘behind’ the light and 1.0 m ‘in front’ of the light. Samples were collected and analyzed for iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), and selenium (Se) at six sample dates from the late fall to early spring for two consecutive years, but only one year for Se. There was no difference between normal and extended daylength for Fe, Cu, Zn, and Mn. Forage Cu concentrations increased with extended daylength for Florona stargrass (from 20.3 to 23.1 ppm). Florona stargrass had the highest forage Zn concentrations (90.7 ppm) with normal daylength and had the highest forage Fe and Cu concentrations (130.0 and 23.1 ppm, respectively) with extended daylength. Pensacola bahiagrass had the highest forage Mn concentrations (250.8 ppm) with normal daylength. Forage Se concentrations increased with extended daylength (from 0.033 to 0.042 ppm). Forage Se had the greatest increase with extended daylength for Tifton-85 bermudagrass from 0.028 to 0.049 ppm. The extended daylength did not have a practical difference for concentrations of the five trace minerals. Therefore, there was no improvement on the nutritive value of the forage with an extended daylength. Only forage Se concentrations increased with an extended daylength; however, this was still insufficient to meet the requirements for beef cattle. Iron, Cu, Zn, and Mn concentrations in these four grasses met the requirements for beef cattle. *Florida Agriculture Experiment Station Journal Series Number R-08263.