bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Factors Related to Wheat Yield on Farm Fields in the Buberuka Highlands of Rwanda
Authors: Burleigh J. R. , Yamoah C. F. , Regas J. L. , Eylands Val J. 
Published: July 2010

AbstractThe wheat (Triticum aestivum L.) improvement program in Rwanda has focused on disease resistance, but other factors, including site characteristics, may impact on cultivar performance. The objectives of this study were to identify on farm fields those factors related to wheat yield that may enhance the wheat improvement strategy. Soil samples from 25 fields in 1988 and 30 in 1989, were analyzed for chemical properties. Fields were characterized by slope, azimuth, irradiance, and disease severity. Grain yield and yield components were regressed on soil and site characteristics, and disease development. Nitrogen and Al explained 35% of the variability in tiller and spike numbers for 1988; whereas, slope and stripe rust severity comprised the best model for 1989. For combined seasons, N and Al, powdery mildew and stripe rust severities, and field slope explained 55% of the variability in tiller and spike numbers. Tillers and spikes per square meter also were correlated as a second degree polynomial with irradiance and maximum numbers occurred at 28 MJ m−2 d−1. Aluminum and N were significant variables for grains per spike in 1989, and their regression coefficients usually were not significantly different among seasons. Among most yield components their standard partial regression coefficients usually were greater than for other independent variables. Azimuth and slope were model components for grains per spike, kernel weight, and grain yield. Responsiveness to N and tolerance to Al, therefore, are important selection criteria and the continued search for resistance to Puccinia striiformis West, and Erysiphe graminis DC. f. sp. tritici E. Marchal is warranted. Yields could be improved by selecting lines that tiller well under high solar flux and testing early generations on sites representative of the region.
Pickup Attachment for Small‐Plot Combine
Authors: Ehrensing D. T. , Crane J. M. , Bolton F. E. 
Published: July 2010

AbstractResearch scale combines currently available are not designed to harvest windrowed seed crops. A pickup attachment was constructed from a commercially available unit that allows mechanized harvest of windrows with plot‐scale combines. This piece of equipment was used successfully during the 1989 season to harvest a variety of seed crops.
Productivity and Quality of Annual and Perennial Clover‐Tall Fescue Mixtures
Authors: Pederson G. A. , Brink G. E. 
Published: July 2010

AbstractWinter annual legumes seeded in perennial clover‐tall fescue pastures could increase early spring herbage production without N fertilizer. This study determined the productivity and forage quality of ‘Regal’ white (Trifolium repens L.) and ‘Kenland’ red clover (T. pratense L.)/tall fescue (Festuca arundinacea Schreb.) mixtures grown with and without ‘Yuchi’ arrowleaf (T. vesiculosum Savi.), ‘Tibbee’ crimson (T. incarnatum L.), and ‘Meteora’ subterranean clover (T. subterraneum L. var. yanninicum [Katzn. & Morley] Zoh.). The experimental design was a split plot with four replicates. Whole plots were red, white, red + white, and no perennial clover. Subplots were arrowleaf, crimson, subterranean, and no annual clover. All species were broadcast seeded on a Catalpa silty clay (fine, montmorillonitic, thermic Fluvaquentic Hapludoll) at Mississippi State, MS, in October 1984. The annual clovers were reseeded in September 1985 and 1986. Arrowleaf and crimson clover competition resulted in 11% less total dry matter and 16% less clover yield compared to no annual clover in perennial clover plots during the first 2 yr of the study. The only yield advantage for perennial clover/tall fescue mixtures with arrowleaf or crimson clovers was in the third year when perennial clover stands declined (mainly due to dry weather conditions) and annual clover overseeding gave 114% greater clover yields. Subterranean clover had little effect on yield or forage quality when grown with perennial clovers. Crude protein and in vitro digestible dry matter concentrations were increased in early spring 1985 and 1987 by the addition of arrrowleaf or crimson clovers to perennial clover plots.
Soil and Canopy Energy Balances of a Row Crop at Partial Cover
Authors: Ham J. M. , Heilman J. L. , Lascano R. J. 
Published: July 2010

AbstractWhen crops are grown in a row configuration, heat and mass transfer within the soil‐canopy system influence the energy and water balance of the crop. Field experiments were conducted near Lubbock, TX, to examine the energy balance of the soil and canopy separately, in cotton (Gossypium hirsutum L.) under a variety of aerial and soil moisture conditions. Bowen ratio techniques were used to obtain the field energy balance, including total latent heat flux (LE). Latent heat flux from the crop canopy (LEc was determined from sap flow measurements of transpiration. Latent heat flux from the soil (LEs) was computed as the daerence between LE and LEc. These measurements were coupled with radiation measurements at the soil surface to partition the energy balance into soil and canopy components every 12 min throughout the day. Results indicate that detailed measurements of energy exchange within the soil‐canopy‐atmosphere system can be obtained without making simplifying assumptions about energy transfer. Daily energy balances were strongly influenced by sensible heat transport, and the radiation balance alone did not account for the magnitude or diurnal pattern of LES and LEC. When the soil surface was dry, the canopy simultaneously absorbed sensible heat originating from the soil and above‐canopy air, accounting for more than 21 and 12% of LEC respectively. After an irrigation, LES accounted for more than 50% of LES even when the leaf area index was greater than two, and 11 to 21% of daily LEC occurred at night. The soil surface absorbed sensible heat from the canopy after irrigation, which increased LE1 while decreasing LEC. Analysis indicates that within‐canopy radiative and convective energy transfer must be considered to accurately characterize LES and LEC in row crops during periods of partial cover.
Soybean Stem Growth under High‐Pressure Sodium with Supplemental Blue Lighting
Authors: Wheeler R. M. , Mackowiak C. L. , Sager J. C. 
Published: July 2010

AbstractHigh‐pressure sodium (HPS) lamps are popular for plant lighting because of their high energy conversion efficiencies. Yet their spectrum has very little blue light (BL), which may cause undesirable morphological responses. To study this, ‘McCall’ soybean [Glycine max (L.) Merr.] plants were grown for 28 d in growth chambers using HPS lamps, with or without supplemental light from blue phosphor fluorescent lamps. Total photosynthetic photon flux (PPF) levels (including blue fluorescent) were kept near 300 or 500 µmol m−2 s−1. Blue fluorescent levels ranged from 7 to 20 µmol m−2 s−1, providing from 6 to 18 µmol m−2 s−1 of supplemental BL (400‐500 nm). Stem and internode lengths were longest under 300 µmol m−2 s−1 HPS lighting and became progressively shorter with increasing supplemental BL until a total of approximately 30 µmol m−2 s−1 of BL (from HPS and BL supplement) was present in the spectrum. Beyond this, extra BL had no effect. Two other lamps rich in BL, metal halide (Optimarc) and fluorescent (Vita‐Lite), also produced plants with short stems, as did HPS lighting maintained at 500 µmol m−2 s−1. Results suggest that use of high‐pressure sodium or other blue‐deficient sources for lighting at low to moderate photosynthetic photon flux levels may cause abnormal stem elongation, but this can be prevented by adding a small amount of supplemental blue light.
Bite Dimensions and Herbage Intake by Cattle Grazing Short Hand‐Constructed Swards
Authors: Ungar E. D. , Genizi A. , Demment M. W. 
Published: July 2010

AbstractThe objectives of this study were to contribute to the understanding and quantification of the effect of sward structure on the ingestive behavior and intake of livestock. Hand‐constructed swards of approximately 0.43 m2 were used to determine the bite dimensions, bite weight, and short‐term intake rate of steers (Bos taurus L.) grazing short swards. Swards were constructed of leaf blades of Paspalum dilatatum Poir. at homogeneous heights of 0.04, 0.06, 0.08, and 0.10 m and heterogeneous heights with means of 0.06 and 0.10 m at two leaf densities. Treatments were replicated using three 4‐yr‐old steers. Bite depth (B) was defined as the initial sward height (H) minus the mean residual height of grazed leaves. Bite area (A) was defined as the surface area represented by the mean number of leaves grazed per bite. Leaf density had no effect on bite dimensions. Linear regression of B on H and linear regression of A on H explained 99% and 89% of the variance, respectively. Mean bite weight ranged from 0.053 to 0.807 g. Correlation of measured bite weight with the product of the measured B, A, and bulk density yielded a coefficient of determination of 0.97. Mean intake rate ranged from 131 to 1473 g h−1. Bite weight accounted for 93% of the variance of intake rate. Bite dimensions on heterogeneous swards were similar to those on homogeneous swards, though by different mechanisms. The importance of biting overlap, leaf insertion in the mouth, and tongue sweeping are discussed in relation to mean bite dimensions and weight.
Water Deficit Effects on Maize Yields Modeled under Current and “Greenhouse” Climates
Authors: Muchow R. C. , Sinclair T. R. 
Published: July 2010

AbstractThe availability of water imposes one of the major limits on rainfed maize (Zea mays L.) productivity. This analysis was undertaken in an attempt to quantify the effects of limited water on maize growth and yield by extending a simple, mechanistic model in which temperature regulates crop development and intercepted solar radiation is used to calculate crop biomass accumulation. A soil water budget was incorporated into the model by accounting for inputs from rainfall and irrigation, and water use by soil evaporation and crop transpiration. The response functions of leaf area development and crop gas exchange to the soil water budget were developed from experimental studies. The model was used to interpret a range of field experiments using observed daily values of temperature, solar radiation, and rainfall or irrigation, where water deficits of varying durations developed at different stages of growth. The relative simplicity of the model and its robustness in simulating maize yields under a range of water‐availability conditions allows the model to be readily used for studies of crop performance under alternate conditions. One such study, presented here, was a yield assessment for rainfed maize under possible “greenhouse” climates where temperature and atmospheric CO2 concentration were increased. An increase in temperature combined with decreased rainfall lowered grain yield, although the increase in crop water use efficiency associated with elevated CO2 concentration, ameliorated the response to the greenhouse climate. Grain yields for the greenhouse climates as compared to current conditions increased, or decreased only slightly, except when the greenhouse climate was assumed to result in severely decreased rainfall.
Canopy Structure and Nutritive Value of Limpograss Pastures during Mid‐Summer to Early Autumn
Authors: Holderbaum J.F. , Sollenberger L.E. , Quesenberry K.H. , Moore J.E. , Jones C.S. 
Published: July 2010

AbstractCattle (Bos spp.) grazing warm‐season, perennial grasses in the lower Southeast USA often gain at a slower rate during mid‐summer to early autumn than they do before or after this season. This has been observed with ‘Floralta’ limpograss [Hemarthria altissima (Poir.) Stapf et C.E. Hubb.], and speculation is that low average daily gains (ADG) may result from changes in canopy structure or herbage nutritive value. During four consecutive 21‐d periods beginning in July 1987 and 1988, a study was conducted on Pomona sands (sandy, siliceous, hyperthermic Ultic Haplaquods) to detect periods of low ADG on rotationally grazed limpograss, and to determine if changes in canopy structure or herbage nutritive value occurred concurrently. Canopies were stratified into two layers of equal depth during each period to characterize herbage bulk density, plant part composition, herbage crude protein (CP), and in vitro digestible organic matter (IVDOM). Additionally, the potential of limited protein supplementation [none, 0.63 kg d−1 (LO) of a 21% CP corn (Zea mays L.)‐urea mixture, or 0.73 kg d−1 (HI) of a 50% CP corn‐urea mixture] to prevent the decline in ADG of steers grazing limpograss was evaluated. Daily gains of steers receiving the 50 and 21% CP supplement treatments (0.59 and 0.53 kg, respectively) were greater than those of nonsupplemented steers (0.29 kg) during the 84‐d trial. Regardless of supplement treatment, steer ADG was lowest during the second period in 1987 (30 July‐20 August) and third period in 1988 (25 August–15 September). Upper (UL) compared with lower canopy layer (LL) had three to six times greater leaf blade to stem plus sheath ratio, 30 to 50% as great a bulk density, 5 to 10% greater IVDOM, and 25 to 100% greater CP. Canopy factors associated with low gain were not identified conclusively, but during periods of low steer ADG, LL stem plus sheath mass was greater than for other periods, whole canopy CP concentration was lower or tended to be lower, and pregraze canopies were tall (57–60 cm), possibly indicating greater physiological maturity of herbage.
Influence of Soil pH and Fertility Programs on Centipedegrass
Authors: Johnson B.J. , Carrow R.N. 
Published: July 2010

AbstractImproper Centipedegrass [Eremochloa ophiuroides (Munro) Hack] fertilization often results in a lower quality turf and progressive decline. Since the grass is best adapted to low fertility and the optimum pH range is uncertain, an experiment was initiated at Griffin, GA, to determine the influence of soil pH and fertility programs on centipedegrass. Soil pH did not influence the growth of Centipedegrass during the first 2 yr after sprigging (1986 and 1987) when the annual fertility program (N‐P‐K, kg ha−1) was ≥100‐44‐83. When N‐P‐K was reduced ≤50‐22‐42 kg ha−1, centipedegrass growth in soil with pH of 6.2 or 6.7 was better than at 5.1. Soil pH did not influence turf quality or density from 1988 through 1990 when fertilized with 100‐44‐83 kg N‐P‐K ha−1. However, soil pH influenced the quality and density of centipedegrass when fertilized at rates greater than 100‐44‐83 kg NP‐K ha−1. Decline of centipedegrass occurred during spring 1988 when the grass was treated with 200‐88‐166 kg N‐P‐K ha− and grown in soil with pH ≥ 6.2 compared with no decline when grown in soil with pH 5.1. Turf quality and density in 1990 was higher in late April when the grass was grown in soil with pH of 6.2 than 5.1, but soil pH differences were not observed by late May. Therefore, soil pH level was not an important factor when fertilized annually at 100‐44‐83 kg N‐P‐K ha−1, but at lower fertilizer rates, the growth was best during the first 2 yr after sprigging when pH was ≥6.2
Leaflet and Canopy Photosynthesis of Peanut Affected by Late Leaf Spot
Authors: Bourgeois G. , Boote K.J. 
Published: July 2010

AbstractLate leaf spot, induced by Cercosporidium personatum (Berk. & Curt.) Deighton, is the most important foliar disease affecting peanut (Arachis hypogaea L.) in Florida and neighboring states. The disease first occurs as necrotic lesions on peanut leaflets and subsequently induces leaflet abscission. Field experiments were conducted to study the effects of late leaf spot on leaflet and canopy photosynthesis. Fully expanded leaflets at the tip of the main stem were tagged and leaflet photosynthesis was measured during the subsequent weeks with a portable photosynthesis system. Leaflet photosynthesis was reduced linearly with the increase in the percentage of necrotic leaf area. Reduction in light utilization due only to necrotic leaf area did not explain completely the reduction in leaflet photosynthesis. Regression analysis suggested that 15% necrotic leaf area contributed to a 65% reduction in the photosynthesis of infected leaflets. It appears that there was an effect on leaflet photosynthesis due to host cells invaded or affected by the pathogen. A chamber made of aluminum frame covered with mylar film was used to estimate canopy photosynthesis over a land area of 0.56 m2. At the canopy level, the effect of reduction in leaflet photosynthesis was negligible compared to the effect of disease‐induced defoliation. The decrease in leaf area index was the major component involved in the reduction of canopy photosynthesis because of the effect of late leaf spot. Canopy photosynthesis was inversely proportional to total disease severity, which is an expression of both defoliation and necrotic area.
Response of Three Quackgrass Biotypes to Nitrogen Fertilization
Authors: Tardif Francois J. , Leroux Gilles D. 
Published: July 2010

AbstractVariability in the response of quackgrass [Elytrigia repens (L.) Nevski] biotypes to N is worth considering if quackgrass is to be used as a forage crop. This study was conducted to determine whether the growth response of quackgrass to different N rates varies among biotypes. The effect of 0, 150, 250 kg N ha−1 on the number of tillers and rhizome buds, total biomass, shoot and rhizome biomass, and shoot to rhizome biomass ratio of three biotypes grown on a St‐Nicolas gravelly loam (loamy, mixed mesic, Typic Dystrochrept) was measured at Ste‐Foy, Québec, Canada, in 1985 and 1986. The response of biotypes to N differed for all variables. At Harvest 1 of 1985 and at Harvests 1 and 2 of 1986, dry matter production of Biotype 3 was at least two times more important at 250 kg N ha−1 than at 0 kg N ha−1. Biotype 1 response to N was comparable to that of Biotype 3 in 1986, but not in 1985. Biotype 2 response to N was inferior to that of the other biotypes and was significant only at the first harvest of 1986. Variations found between years are attributed to differences in rainfall regime. The response of a quackgrass biotype to N is to be considered if it is to be used as a forage crop or in a breeding program.
Agronomic and Economic Response of Spring Wheat Cultivars to Ethephon
Authors: Khan A. , Spilde L. 
Published: July 2010

AbstractEfforts to optimize grain yields in wheat (Triticum aestivum L.) are often hindered by excessive lodging associated with intensive cereal management systems. The plant growth regulator ethephon [(2‐chloroethyl) phosphonic acid] has been used as an essential component of intensive cereal management systems in Europe to control lodging and maintain high yield potential. The objective of this study was to determine the effect of ethephon on four hard red spring wheat cultivars in North Dakota environments. A randomized complete block design in a split plot arrangement with four replicates was used at each of four locations in 1987 and 1988. Main plot treatments consisted of the cultivars Era, Stoa, Len, and Nordic, and split plots were assigned to ethephon and control (no ethephon). Application of ethephon (280 g a.i. ha−1) increased grain yield 5.4% when averaged across environments and cultivars. Generally, ethephon application tended to increase spikes per square meter but had no effect on kernel weight and kernels per spike. Ethephon treatment reduced lodging in 1987. Lodging was absent in 1988. Application of ethephon had a significant positive effect on test weight, but did not influence grain protein concentration and maturity. Economic parameters, net benefit, and marginal rate of return, indicated ethephon could be recommended for cultivars Era, Len, and Stoa, but not for Nordic under environmental conditions similar to those in this study.
Rubber and Resin Yield Performance of New Guayule Selections
Authors: Estilai A. , Ehdaie B. , Naqvi H. H. , Dierig D. A. , Ray D. T. , Thompson A. E. 
Published: July 2010

AbstractGuayule (Parthenium argentatum Gray) is a promising alternative to the rubber tree (Hevea brasiliensis Muell. Arg.) for domestic production of natural rubber in semiarid regions. Guayule is not yet a crop and its commercialization will depend on the development of high rubber‐yielding cultivars. The objectives of this study were to determine if individual plant selection has been effective in improving rubber yield; to determine the suitability of California selections for rubber and resin production in Arizona; and to examine the extent of genotype‐by‐environment (G ✕ E) interactions in improved guayule selections. Plant height, width, dry weight, rubber content, resin content, rubber plus resin content, rubber yield, resin yield, and rubber‐plus–resin yield were measured for 24 guayule genotypes planted at Riverside and Palmdale, CA, and Maricopa, AZ, from 1986 to 1989. Genotypes were significantly different for all traits except for plant width and dry weight at Maricopa. The highest rubber yields were 743 kg ha−1 yr−1 at Riverside, 172 at Palmdale, and 564 at Maricopa. Genotype A9 at Riverside and Genotype A22 at Maricopa exceeded the mean rubber yield of two standard varieties by 163 and 66%, respectively, indicating that selection for increased rubber yield within heterogeneous germplasm has been successful. The highest resin yield was 1405 kg ha−1 yr−1 at Riverside, 668 at Palmdale, and 1006 at Maricopa. With rubber plus resin yields of 2085 and 1579 kg ha−1 yr−1, Genotypes A4 and A22 appear acceptable for large‐scale production at Riverside and Maricopa, provided economic markets are found for guayule resin. The G ✕ E interaction effects were significant for all traits. Analyses of data suggested that both quantitative and qualitative differences in performance of genotypes in different locations were responsible for the observed G ✕ E interactions.
Iron Fertilization Effects on Shoot/Root Growth, Water Use, and Drought Stress of Creeping Bentgrass
Authors: Glinski D. S. , Carrow R. N. , Karnok K. J. 
Published: July 2010

AbstractCreeping bentgrass (Agrostis palustris Huds.) golf greens in the U.S. Southeast are subjected to summer drought and heat stresses. This study was initiated to determine the effects of foliar Fe on FC‐sufficient bentgrass shoot responses, root growth, and respones to drought stress. Ferrous sulfate (FS), Lawn‐Plex (LP), and Sequestrene 330 (Seq. 330) (FeSO4‐7H2O; Fe phosphate‐citrate; and sodium ferric diethlenetriamine‐pentaacetate, respectively) were applied to a golf green at 1.12 kg Fe ha−1 per month for a 17‐mo period. All Fe sources improved color and visual quality throughout the year; summer color improved 5.9% compared to 8.6 to 9.5% for all other seasons. Total extractable tissue Fe was not well correlated with color (r < 0.54). Iron carriers had different effects on growth, especially between late summer and winter. Lawn‐Plex increased cool‐season clipping yields while Seq. 330 reduced verdure in the summer by 18% compared to the control. Root growth (weight and length) was equal to, or less than the control for all Fe treatments. In August, FS‐treated plants exhibited a 31% decrease in root length density (RLD) in the 0 to 10 cm zone. In October, 10‐ to 20‐cm depth RLDs were reduced relative to the control by 31% for FS and 28% LP for treatments. While LP tended to reduce rooting, it was the only Fe carrier to exhibit consistently better (15– 40%) soil moisture extraction than the control. Iron had no apparent effect on canopy temperature as a stress indicator. Since shoot growth, root growth, and water extraction responses often varied with Fe carrier, many reported Fe effects are probably due to the carrier rather than Fe. Exceptions would be the color and visual quality improvements observed for all Fe carriers.