bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early Growth and Dinitrogen Fixation by Arrowleaf Clover in Response to Starter Nitrogen
Authors: Schomberg H. H. , Weaver R. W. 
Published: July 2010

AbstractSeedling vigor of arrowleaf clover (Trifolium vesiculosum L. Savi) is poor but it may be enhanced by application of starter mineral N. Three experiments were conducted using a growth chamber and a glasshouse to determine the influence of starter mineral N and strains of Rhizobium leguminosarum biovar trifolii on dry matter production and N2 fixation of arrowleaf clover. In one experiment, seeds were planted in a N‐deficient medium, inoculated with two strains of rhizobia and provided with five levels of mineral N. The lowest level of mineral N doubled seedling dry weights and the amount of biologically fixed N in 40‐d‐old seedlings. Rhizobial strain interacted with mineral N in influencing dry matter production and N2 fixation. To further examine the influence of rhizobial strain, five additional strains varying in effectiveness were evaluated in a second experiment. Mineral N provided to plants inoculated with any strain increased dry matter production and N2 fixation. To aid in extrapolating the response of arrowleaf clover seedlings to mineral N, seed were sown into undisturbed soil cores from four fields. The cores were fertilized with the equivalent of 0, 31, and 62 kg N ha−1. Fertilization with 31 kg of N did not reduce N2 fixation by plants grown on cores of soil collected from three fields and dry matter production was nearly doubled on cores from two fields. Providing some mineral N to arrowleaf clover seedlings greatly enhanced seedling vigor.
Exact Equations for Calculating Air Leakage Rates from Plant Growth Chambers
Authors: Kimball B. A. 
Published: July 2010

AbstractThe rates of leakage of CO2 from plant assimilation chambers must be known in order to correct measurements of net photosynthesis and respiration for this unwanted but omnipresent source of error. Similarly, in order to precisely calculate heating or cooling requirements for plant growth structures, air leakage or “infiltration” must be known. The objective of this paper is to derive theoretically exact equations for calculating such leakage rates from measurements of CO2 concentration [CO2]. The needed equations were derived from the solution of a basic differential CO2 balance equation. The procedure presumes the determination will be done when plant CO2 exchange is steady, a condition most nearly satisfied by respiration near the end of the night. The equation had two unknowns, respiration and leakage rate. From measurements before and after a CO2 perturbation, it was possible to derive sets of two equations with two unknowns, which were then solved for the respiration and leakage rates. In contrast to prior work, the new equations are theoretically exact, and they can account for changes in ambient [CO2] during the measurement periods and also for differing rates of CO2 injection before and after the perturbation. Moreover, these theoretically exact equations are no more complex than the prior approximate equations for a couple of practical cases. Calculations for three specific cases showed the approximation used in the prior equations introduced errors of 0.8, 5.5, and 1.6%. Thus, using these equations derived in this paper should permit more accurate calculations of leakage rate and ultimately, therefore, more accurate determinations of gas exchange rates from plants in assimilation chambers as well as of the heating or cooling requirements of the chambers themselves.
Root Development of 12 Forage Legumes as Affected by Temperature
Authors: Brar G. S. , Gomez J. F. , Matches A. G. , Taylor H. M. , McMichael B. L. 
Published: July 2010

AbstractLegumes with roots that elongate rapidly over a wide temperature range should have improved seedling establishment semiarid regions. We determined effects of 10, 15, 20, 25 and 30 °C temperature on main axis and lateral root growth of 12 forage legumes in germination chambers. Legumes differed (P < 0.05) in both main axis root length and lateral root development over temperatures and there were significant (P ° 0.05) entry by temperature interactions. There were significant positive non‐linear correlations with (R2,) of 0.72, 0.68 and 0.76 at 15, 20 and 25 °C temperatures, respectively, between seed weight and main axis root elongation.
Impact of Insect Feeding on Alfalfa Regrowth: A Review of Physiological Responses and Economic Consequences
Authors: Hutchins Scott H. , Buntin G. David , Pedigo Larry P. 
Published: July 2010

AbstractInsect‐induced injury to alfalfa, Medicago sativa L., has been a frequent topic of research. The central focus of many investigations has been the physiological response of alfalfa to insect feeding, measured as altered root carbohydrate levels, canopy development, and forage feeding value. Leaf‐mass consuming insects generally either remove leaf tissue in aerial portions of established canopies (e.g., alfalfa weevil, Hypera postica [Gyllenhal]) or consume new foliage during early regrowth (e.g., variegated cutworm, Peridroma saucia [Hubner]). In both instances, injury results in an initial reduction in leaf‐to‐stem biomass (L/S) ratio. Continued defoliation, however, affects canopy photosynthesis to the point that stem growth is slowed. Assimilate‐removing insects (e.g., potato leafhopper, Empoasca fabae [Harris]), disproportionately reduce stem growth compared to leaf growth, resulting in a higher L/S ratio. Although specific host response varies across the range of piercing‐sucking insects, herbage feeding value per plant mass is generally enhanced with the increased L/S ratio. Overall, insect‐induced changes in yield and quality from leaf‐mass and assimilate removal consequentially reflects a delay in maturity. From a crop management perspective, slowed phenological development may alter harvest schedules or disrupt necessary root carbohydrate regeneration. Specific knowledge of host response, combined with current economic circumstances, should serve as a basis for developing economic injury levels to manage insect pests.
Sunflower Production as Influenced by Plant Type, Plant Population, and Row Arrangement
Authors: Zaffaroni Eduardo , Schneiter A. A. 
Published: July 2010

AbstractSemidwarf sunflower (Helianthus annuus L.) hybrids recently became available to producers. Information on the response of this plant type to different cultural practices is limited. Field studies were conducted at two locations in 1984, 1985, and 1986, to determine the effect of different row arrangements and plant populations on yield, yield components, and other agronomic traits of a semidwarf (SD) and a standard height (SH) sunflower hybrid. Plant populations evaluated were 35 000, 50 000, and 65 000 plants ha−1. Row arrangements evaluated consisted of (i) conventional rows, spaced 0.76 m apart, (ii) solid seeded rows, spaced 0.38 m apart, and (iii) twin rows, two rows 0.19 m apart on 0.76 m centers. A path coefficient method was used for yield component analysis. Analyses across environments indicated no statistical differences for yield among hybrids, plant populations, or row arrangements. Significant environment ✕ hybrid, environment ✕ row arrangements and environment ✕ arrangement ✕ population interactions on yield were found. The SH type outyielded the SD at all environments, although statistically significant differences were found in only four of the six environments. In general, plant population and number of seeds per head were the yield components having the greatest direct effect on yield. The direct response of plant population was masked by the negative effect of seeds per head and seed weight, resulting in a low coefficient of correlation. Harvest index of SH (36%) was statistically higher than for the SD (32%). The difference was due to the heavier receptacle of the SD. This indicates that possibilities exist to improve semidwarf genotype yield by reducing receptable weight.
Simultaneous Selection for High Yielding and Stable Crop Genotypes
Authors: Kang M. S. , Pham H. N. 
Published: July 2010

AbstractIntegration of stability of performance with yield is essential in yield trials. Methods that select for high yield and stability have been developed, but have not been compared for their usefulness. Our objective was to compare these methods and to study their relationship to yield and the stability‐variance statistic (σ2i). We compared Kang's (1988b) rank‐sum method (Index 1; equal weights for yield and σ2i) and four additional rank‐sum indices [two (Index 2), three (Index 3), four (Index 4), and five (Index 5) times more weight for yield than for stability variance] with Hühn's (1979) S3i and S6i statistics, and Lin and Binns' (1988) Pi. All statistics were calculated for each of five sets of data from international maize (Zea mays L.) yield trials. In Set 1, low σ2i's (indicative of stable performance) were generally associated with high yield (r3 = 0.73), but in Set 2 low σ2i's appeared to be associated with low yield (r3 = −0.46). Index 1 ranks were positively correlated with σ2i ranks in Sets 2 to 5 as were S3i ranks. Index 1 and S3i offered an opportunity to select for both stability based on σ2i and yield. Indices 2, 3, 4, and 5, and Pi favored selection primarily for yield. It was assumed that the top 50% genotypes would be selected, in Sets 1 and 2, on the basis of yield rank alone or individual statistics. In Set 1, Index 1 was slightly more conservative than S3i, in that Index 1 selected a higher yielding genotype from the two lowest yielding genotypes than did S3i. S6i was slightly more conservative than Index 1. Index 1 was intermediate between S3i and S6i. In Set 2, Index 1 and Index 2 were more conservative than σ3i, whereas σ6i was more conservative than Index 1, but less conservative than Index 2. Pi favored selection for yield only. We concluded that Kang's rank‐sum method (Index 1 here) and Hühn's S3i and S6i statistics would be useful for simultaneously selecting for yield and yield stability.
Timing and Nature of Mulch Retardation of Corn Vegetative Development
Authors: Fortin M.‐C. , Pierce F.J. 
Published: July 2010

AbstractLow soil temperatures that are induced by crop residue have been shown to delay corn (Zea mays L.) development. The exact conditions under which retardation takes place and whether the delay is only due to thermal effects still need to be elucidated. This study was conducted to characterize corn vegetative development, with and without residue cover, and to determine if differences in seed‐zone temperature account for the differences in development. The effects of an oat (Avena sativa L.) straw mulch and an inert poplar excelsior (Populus) mulch, applied at second leaf tip emergence and at the time of full extension of the fourth leaf, on seed‐zone temperature, time, and thermal time (daily temperature accumulation) between specific vegetative stages, were investigated on a Conover loam (mixed, mesic, Udollic Ochraqualf) under irrigated conditions. Developmental delays occurred as average soil maxima temperatures, under the mulches, were 2.2 °C lower than the bare soil control. When mulches were applied at second leaf tip emergence, soil temperature‐based thermal time was significantly higher for the oat mulch than for the popular mulch or the bare soil, until the full extension of the fourth leaf in 1988 and the third leaf in 1989. Modeling equations derived from CERES‐MAIZE accurately predicted thermal times to the full extension of the third leaf and sixth leaf for most treatments, but underestimated thermal time for the 1988 oat mulch. When applied at full extension of the fourth leaf, oat straw had minimal effects on development. The differences in thermal time due to the two mulches during the early vegetative stages of corn, suggest that in addition to soil temperature, allelopathy from oat straw may be a source of developmental delay and that its occurrence is weather‐dependent.
Apical Development of Spring Barley in Relation to Chlormequat and Ethephon
Authors: Ma B. L. , Smith D. L. 
Published: July 2010

AbstractThere is considerable interest in the use of plant growth regulators (PGR) to control lodging in spring barley (Hordeum vulgare L.), and to increase the number of spike‐bearing tillers through early application. Application of PGR is likely to have effects on the development of reproductive structures in both main‐stem and tiller apices. The objective of this study was to investigate the timing and dynamics of barley main‐stem apical development as influenced by chlormequat chloride (2‐chloroethyl trimethylammonium chloride; CCC) or ethephon (2‐chloroethyl phosphonic acid) treatment. A 3‐yr field study using widely grown cultivars, ‘Leger’ and ‘Cadette’, was conducted on Bearbrook clay soil (fine, mixed nonacid, mesic Humaquept) at Emile A. Lods Agronomy Research Centre, McGill University, Canada, from 1987 to 1989. Treatments consisted of application with CCC and ethephon at Zadoks growth stages (ZGS) 13, 30, and 39. Data were collected on growth regulator induced plant changes in (i) external morphological characters, (ii) apical development, and (iii) spikelet primordium abortions. Application of CCC at ZGS 13 retarded development of the main‐stem apex from shortly after application to awn elongation and reduced the number of aborted spikelet primordia. Unlike CCC, the retarding effect of ethephon on main‐stem apical development was not shown until a few days after its application (when the maximum number of main‐stem primorida was reached), which may have promoted tiller survival. In general, the application of PGR reduced the apical dominance of dominant sinks (main‐stem apex and/or central spikelets of the rachis) allowing the survival and greater development of more subordinate sinks (tillers and/or distal rachis spikelets).
Lamb Production on Wheatgrasses and Wheatgrass‐Sainfoin Mixtures
Authors: Karnezos T. P. , Matches A. G. 
Published: July 2010

AbstractPrevious research indicates that wheatgrasses (Agropyron and Thinopyron spp.) and sainfoin (Onobrychis spp.) produce high quality forage from early spring to summer on the Southern Great Plains. Little information is available on their potential for lamb (Ovis aries L.) production under grazing. Our objective was to determine levels of spring lamb production from three irrigated wheatgrasses, ‘Hycrest’ [A. cristatum (L.) Gaertner ✕ A. desertorum (Fischer ex Link) Shutters], ‘Luna’ [T. intermedium subsp. barbulatum (Schur) Barkw. and D.R. Dewey], and ‘Jose’ [T. ponticum (Podp.) Barkw. and D.R. Dewey], grown alone and with ‘Renumex’ sainfoin (O. viciifolia Scop.). Replicated pastures grown on a Pullman clay loam (fine, mixed thermic Torrertic Paleustoll) were rotationally grazed (herbage allowance of 6.5% of body wt. d−1) by weaned Rambouillet ✕ Suffolk wether Iambs for an average of 77 d in spring of 1987 and 1988. Seasonal average daily gain (ADG) ranged between 45 and 69 g d−1 for monocultures and between 80 and 104 g d−1 for mixtures. Lamb production per hectare (PROD) for all mixtures was similar (463 kg ha−1), but higher than for monocultures (238 kg ha−1). Mixtures compared to monocultures had greater ADG (63%), feed conversion (55%), and intake (23%). For Jose and Jose‐sainfoin, poor ADG after Week 7 was associated with low herbage crude protein (92‐135 g kg−1) and organic matter digestibility (550‐570 g kg−1). Jose (12.2 Mg ha−1) had the highest herbage accumulation and Hycrest (7.31 Mg ha−1) the lowest. Wheatgrasses, particularly when grown with sainfoin, provide good PROD during spring and early summer.
Grazing Tolerance of Warm‐Season Legumes in Peninsular Florida
Authors: Muir J. P. , Pitman W. D. 
Published: July 2010

AbstractDespite the potential benefits and frequent favorable results in germplasm evaluations, only limited success has been attained in many areas with tropical pasture legumes. Lack of information regarding both germplasm adaptation and pasture management requirements has been a limitation. Five promising perennial species were evaluated for grazing tolerance and response to fall grazing deferment on an Immokalee fine sand (Sandy, siliceous, hyperthermic Arenic Haplaquod) at Ona, FL. Alysicarpus vaginalis DC; Desmanthus virgatus (L.) Willd.; Galactia elliottii Nuttall; G. volubilis (L.) Britton; Vigna adenantha (G. F. Meyer) Marechal, Mascherpa, and Stainier; and the standard ‘Florida’ carpon desmodium [Desmodium heterocarpon (L.) DC] were subjected to three treatments: (i) continuous grazing through the growing season (late May to mid‐December), (ii) continuous grazing with fall deferment (grazed late May to mid‐September), and (iii) an ungrazed control. Legume main plots, 5 by 15 m in a randomized complete block design, were split in a strip‐plot arrangement to give grazing treatment subplots of 5 by 5 m. Legumes were transplanted in 1986, grazed in 1987 and 1988, and evaluated for persistence through the summer of 1989. By December 1988, the prostrate A. vaginalis had the highest (P < 0.05) survival percentage under both grazed treatments. Survival of D. virgatus, G. elliottii, and V. adenantha was generally highest in the ungrazed control. The Galactia species demonstrated superior adaptation to drought during the spring of 1989. Fall deferment consistently increased survival of only G. volubilis and V. adenantha. Tolerance of continuous grazing was suggested only for A. vaginalis and carpon desmodium. Grazing management strategies involving periods of deferment from grazing during the growing season will apparently be necessary for persistence of stands of D. virgatus and G. elliottii.
Dinitrogen Fixation and Nitrogen Balance in Cool‐Season Food Legumes
Authors: Beck D. P. , Wery J. , Saxena M. C. , Ayadi A. 
Published: July 2010

AbstractUnderstanding the magnitude of N2 fixation and export of plant N, particularly in the harvested grain and straw, is necessary to assess the potential for grain legumes to contribute to long‐term agricultural production stability. The proportions of total plant N derived from N2 fixation in four grain legume crops, faba bean (Vicia faba L.), chickpea (Cicer arietinum L.), lentil (Lens culinaris L), and pea (Pisum sativum L.), were estimated in three field experiments conducted for two seasons in Syria (Vertic Chromoxeralf soil) and one season in France (Calcaric Cambisol). Since cultural practices and cultivars affect grain yield, the impact on N2 fixation of sowing date in chickpea and Sitona insect control in lentil, and of cultivar selection of pea and faba bean, was evaluated. By calculating the proportion of total plant N derived from N2 fixation (%Ndfa) using 15N isotope dilution with barley (Hordeum vulgare L.) and non‐nodulating chickpea as reference crops, the effects of removal of N in grain and straw, relative to N fixed and plant uptake of soil mineral N, were estimated. Pea and lentil had similar %Ndfa values across locations, seasons, and cultural practices, with an average 70%Ndfa. In chickpea, winter sowing increased %Ndfa to 72 from 26% in the spring‐sown crop. Dinitrogen fixation in the spring‐sown crop was higher in France (44%Ndfa), while fixation in the winter crop was higher in Syria (80%). Faba bean obtained 9O%Ndfa in France, but only 69% in Syria. The large‐seeded type fixed higher N (74%Ndfa) than the small‐seeded type (64%) in Syria but not in France. The calculated N balance where only grain was removed ranged from 44 kg N ha‐' net gain to 44 kg N ha−1 loss. Where both seed and straw were removed, nearly all calculations were negative, with loss of up to 70 kg N ha−1 from soil.
Phyllochron Change in Winter Wheat with Planting Date and Environmental Changes
Authors: Cao Weixing , Moss Dale N. 
Published: July 2010

AbstractThe phyllochron (degree‐days/leaf) of wheat (Triticum aestivum L.) differs with planting dates and latitudes. An understanding of the causes for these differences is needed to model the development of wheat crop canopies. Stephens and Yamhill winter wheat cultivars were planted on a range of dates in outdoor pots and in field plantings to study the relationship of phyllochron to the daylength and mean air temperature at seedling emergence. Both cultivars had a nearly constant phyllochron for a given planting in both pot and field plantings until 600 cumulated degree‐days (CDD), which was about the time of double ridge formation. Phyllochron values were different, however, for the different planting dates. At about 600 CDD the phyllochron increased in 18 of 20 cultivar‐planting date combinations. Fifty to 60% of the variation in phyllochron prior to double ridge formation could be normalized by either the thermo/photo ratio at seedling emergence (mean temperature to photoperiod) or by the rate of change of photoperiod. These two methods have been suggested previously to normalize phyllochron for differences due to different planting dates. After 600 CDD the phyllochron was not related to thermo/photo ratio, the rate of change of photoperiod, maximum or minimum temperatures, photoperiod or its inverse, or the intensity of solar radiation. Thus, use of a constant value for phyllochron in dynamic crop models of wheat leaf development is not appropriate for all circumstances.
Correction for Slope in Green Speed Measurement of Golf Course Putting Greens
Authors: Brede A. D. 
Published: July 2010

AbstractGreen speed of golf course putting greens (an inverse function of the surface friction) is assessed by use of a stimpmeter, a widely used tool distributed by the United States Golf Association. However, green speed of sloped surfaces cannot be measured satisfactorily due to the distorting effects of downslope gravitational acceleration of the ball. The purpose of this study was (i) to develop a simple equation that could be used to correct for the effects of gravitational acceleration on sloped greens, and (ii) to verify the new equation: Corrected green speed = 2S↑S↓ (S↑S↓)−1, where S↑ = distance of ball roll directly uphill and S↓ = distance of ball roll downhill. A laboratory carpet‐covered runway apparatus and two field putting greens were used for validation. Laboratory green speed readings corrected with the equation were equal, regardless of slope from 0 to 5.6%. By using the equation, a golf course superintendent can check green speed of sloped areas that previously would have been impossible to assess.
Root Response of Tolerant and Intolerant Soybean Cultivars to Soybean Cyst Nematode
Authors: Miltner E. D. , Karnok K. J. , Hussey R.S. 
Published: July 2010

AbstractTolerance to soybean cyst nematode (SCN), Heterodera glycines Ichinohe, has been identified in soybean [Glycine max (L.) Merr.] and has potential as a management strategy to limit SCN yield suppression. Little information is available on the growth and morphology of roots of tolerant soybean cultivars parasitized by SCN. This study was conducted to compare root and vegetative responses of a moderately tolerant soybean, ‘Wright’, with an intolerant soybean, ‘Bragg’, to parasitism by SCN. In 1986, Bragg and Wright soybean was grown in the University of Georgia rhizotron in rooting medium infested with SCN Race 3 at initial population densities (Pi) of 0, 1000, or 10 000 eggs/L. Measurements were made of soybean root growth and development, vegetative and reproductive growth stage, leaf number, flower and pod numbers, and nematode activity (development and infection). Number of growing roots on Bragg at Pi 10 000 was suppressed throughout the season, whereas root growth of Wright was stimulated by the presence of SCN. Although not statistically significant, root lengths followed these same trends. Seed yield of Bragg was progressively suppressed as Pi increased, in contrast to that of Wright which was suppressed at Pi 1000, but was not suppressed further at Pi 10 000. Vegetative development of Bragg was suppressed at Pi 10 000 compared to Pi 0 from 18 and 39 d after planting (DAP), respectively, in contrast to Wright which was unaffected. Reproductive development of Bragg at Pi 10 000 was also suppressed between 79 and 133 DAP. The stimulation of root development of Wright in the presence of SCN was probably critical to maintenance of vegetative and reproductive development.