bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Shading on the Growth of Some Common Weeds of the Semi‐Arid Tropics1
Authors: Shetty S. V. R. , Sivakumar M. V. K. , Ram S. A. 
Published: July 2010

AbstractLight is one of the major factors influencing crop‐weed balance. The influence of shading on the growth, leaf area, dry matter production, and seed production of some common weeds of the semiarid tropics was investigated in a field study at ICRISAT Research Center near Hyderabad, India, during the 1978 and 1979 rainy seasons. Different shade treatments were achieved by erecting rectangular bamboo frames over each plot. The weeds studied were Cyperus rotundus L., Digitaria ciliaris (Retz.) Koeler, Celosia argentea L., Acanthospermum hispidum DC., Tridax procumbens L., Dactyloctenium aegyptium (L.) P. Beauv., and Amaranthus viridis L. At 90% shading plant height was reduced to 30% of the control with Celosia and Tridax. Digitaria and Dactyloctenium showed 70 to 80% reductions in leaf area index (LAI) at 90% shading. Dry matter production in Digitaria, Dactyloctenium, and Acanthospermum was reduced up to 80% at higher shading levels. In Cyperus, the effect of decreasing light levels on plant height was not pronounced, but the LAI and dry matter production were severely affected. Photosynthetic photon flux density (PPFD) measurements showed a negative correlation between levels of shading and the seed production in these weeds.The study indicated that by manipulating crop canopies to create desired shading, substantial weed suppression could be achieved. The agronomic significance of these results is discussed in the light of the weed‐suppressing capacity of crop canopies in different cropping systems of the semiarid tropics that may complement other control measures to obtain better weed management.
Effects of Lime, P, and Mo Application on Mo Concentration in Subclover1
Authors: Petrie S. E. , Jackson T. L. 
Published: July 2010

AbstractSubterranean clover (Trifolium subterranium L.) is a winter annual legume grown in the hill pastures and hay fields of western Oregon. Soils are acid (pH 4.5 to 5.5) and yield responses to lime, P, and Mo are common. Lime, P, and Mo application can result in increased Mo concentrations in plants. Forage containing more than 10 µg Mo/g is potentially toxic to ruminants. An experiment involving subterranean clover and perennial ryegrass (Lolium perenne L.) was established in the fall of 1976 on a Typic Haploxeralf, fine, mixed, mesic soil to evaluate the effects of lime, P, and Mo applications on: (1) the Mo concentration in subterranean clover leaflets and petioles and in the clover‐grass mixture and (2) the longevity of the treatment effects on Mo concentration in the clover‐grass mixture. Lime was applied at 0, 4.5, or 9.0 metric tons/ha, P was applied as concentrated superphosphate at 0, 19, or 57 kg/ha, and Mo was applied as Na2Mo04 2H20 at 0 or 0.5 kg/ha. All treatments received adequate K, S, and B. Clover leaflet and petiole samples were analyzed to determine the Mo critical level for the clover and establish the maximum Mo concentration that would be consumed by a grazing animal. Clover grass mixture samples were analyzed to determine the average Mo and Cu concentration that would be consumed. The Mo concentration in clover leaflet and petiole samples collected 18 Mar. and 12 Apr. 1977 was increased from 1.5 to over 25 µg Mo/g by application of lime, P, and Mo. The Mo concentration decreased to less than 15 µg/g by 12 May 1977. Application of lime, P, and Mo increased the Mo concentration in the clover‐grass mixture from 1 to over 5 µg Mo/g and decreased the Cu:Mo ratio to below 2, which is potentially toxic to livestock.The highest Mo concentration was less than 10 µg Mo/g in clover leaflet and petiole samples collected the second growing season and the Mo concentration in the clover‐grass mixture was less than 5 µg Mo/g for all treatments except one. The Mo concentration was below 2 µg Mo/g in all samples collected the third growing season. Although the Mo concentration was as low as 0.1 µg/g, yield responses from Mo application were not evident.
Response of Basin Wildrye and Tall Wheatgrass Seedlings to Salination1
Authors: Roundy Bruce A. 
Published: July 2010

AbstractTall wheatgrass [Agropyron elongatum (Host) Beau. ‘Jose’] and basin wildrye (Elymus cinereus Scribn. & Merr. ‘Magnar’) may have high potential for increasing forage production on degraded, saline/alkaline rangelands in the arid west. To compare their tolerance to salinity and decreasing soil osmotic potentials seedlings of each species were grown in salinized sand cultures in the greenhouse with isosmotic solutions of CaCI2, NaCI, Na2SO4, and equimolar CaCI2 plus NaCl and Na2SO4 plus NaCI. Calcium inhibited growth of both cultivars more than the other salts and was especially toxic to basin wildrye seedlings at osmotic pontentials below − 15 bars. Since Na2SO4, and NaCl are the predominant salts on Great Basin saline rangelands, Ca toxicity should not be a problem in field plantings, but high tolerance to Na should have adaptive value for both cultivars. Absolute yield of Jose shoots and roots exceeded that of Magnar at all soil osmotic potentials, but salination reduced root growth of Jose more than Magnar and reduced shoot growth of Magnar more than Jose. Even though both cultivars maintained relatively high turgor at low leaf water potentials small initial losses in turgor were associated with greatly reduced growth. Either the threshold turgor necessary for growth of these cultivars was very high under these experimental conditions or ionic imbalances or energy expenditures associated with osmotic adjustment limited growth despite high turgor pressure. Gradually salinized plants maintained positive turgor at average leaf water potentials of 12 bars lower than did control plants in which water stress developed rapidly due to decreasing soil matric potentials when water was withheld. Both species survived soil osmotic potentials down to ‐35 bars but grew very little below − 10 bars.
Forage Yield, Quality, and Persistence of Switchgrass and Caucasian Bluestem1
Authors: Anderson Bruce , Matches A. G. 
Published: July 2010

AbstractSwitchgrass (Panicum virgatum L.) and Caucasian bluestem [Bothriochloa caucasica (Trin.) C.E. Hubbard] provide forage during summer when cool‐season grasses in the southern Corn Belt are unproductive. Information is limited on the response of these grasses to defoliation, especially the effect of harvest management on regrowth. Field studies on a Creldon silt loam soil (fine, mixed, mesic Mollic Fragiudalf) were conducted to determine forage yield and quality trends and persistence of Switchgrass and Caucasian bluestem as influenced by date of first harvest and stubble height. Five dates of first harvest and two cutting heights (8 and 23 cm) were imposed factorially on established stands of Switchgrass and Caucasian bluestem for 3 years. The first harvests were taken consecutively at 1 week intervals with the initial first harvest made when plants were in a vegetative to early jointing growth stage. When cut at an 8 cm stubble height, first harvest yields of Switchgrass and Caucasian bluestem averaged over 3 years increased 763 and 1,010 kg/ha per week, respectively, with each week delay of first harvest. However, corresponding total regrowth yields/ha declined 424 kg for Switchgrass and 632 kg for Caucasian bluestem. Trends were similar for cutting at a stubble height of 23 cm, but yields were usually less than at 8 cm. Forage in vitro dry matter disappearance declined 2.0 percentage units per week for both Switchgrass and Caucasian bluestem while crude protein declined 1.6 and 1.0 percentage units per week, respectively, with each week delay in first harvest. Neutral detergent fiber (NDF) increased 1.4 percentage units per week for Caucasian bluestem at both stubble heights and for Switchgrass at 8 cm; the NDF of Switchgrass at 23 cm increased 0.4 percentage units per week. Our results indicated that Switchgrass and Caucasian bluestem should be harvested when plants begin to joint. Early harvest results in forage of higher quality and regrowth potential than harvest at later growth stages.
Leaf and Canopy Temperatures of Pearl Millet Genotypes under Irrigated and Nonirrigated Conditions1
Authors: Singh Piara , Kanemasu E. T. 
Published: July 2010

AbstractIt has been reported from previous research that leaf and canopy temperatures correlate with the level of water stress in a plant. If genotypes of a given species differ in their response to water stress, then leaf and canopy temperatures could serve as indices of their drought resistance. To test this hypothesis, 10 pearl millet (Penniserum americanum (L.) Leeke) genotypes differing in plant morphology were grown on a Eudora silt loam soil (fine silty, mixed, mesic, Pachic Haplustoll) under both irrigated and nonirrigated conditions. Leaf temperature (Tl), canopy temperature (Tc), canopy minus air temperature (Tc – Ta), leaf‐water potential (Ψl), leaf‐diffusion resistance (LDR), water use (WU), and crop yields were observed in both irrigated and nonirrigated treatments. Significant differences (P<0.05) were found in the grain yield, Tc, and Tc – Ta of genotypes, only in the irrigated treatment. Grain yield was negatively and significantly correlated with average afternoon Tc(r = −0.81) and average afternoon Tc – Ta(r = −0.78). Grain yield ratio (nonirrigated grain yield/irrigated grain yield) was positively and significantly correlated with average afternoon Tl(r = 0.64), average afternoon Tc(r = 0.64), and average afternoon Tc – Ta(r = 0.75). In the nonirrigated treatment, however, correlations of grain yield and grain yield ratio with various stress indices were nonsignificant. Average afternoon Tc and Tc – Ta was significantly correlated with average afternoon LDR only in the irrigated treatment. This study suggests that average afternoon Tc and Tc – Ta as observed in a nonstressed environment with an infrared thermometer could effectively be used as a technique to screen millet genotypes for their grain yield and grain‐yield stability (nonirrigated grain yield/irrigated grain yield).
Spectral Estimates of Solar Radiation Intercepted by Corn Canopies1
Authors: Daughtry C. S. T. , Gallo K. P. , Bauer M. E. 
Published: July 2010

AbstractAs the need for timely information on worldwide crop production intensifies the role of remote sensing is becoming more prominent. If agronomic variables related to yield could be reliably estimated from multispectral satellite data, then crop growth and yield models could be implemented for large areas. The objective of this experiment was to develop methods for combining spectral and meteorological data in crop yield models that are capable of providing accurate estimates of crop condition and yields. Initial tests of this concept using data acquired in field experiments at the Purdue Agronomy Farm, West Lafayette, Ind., are presented. Reflectance factor data were acquired with a Landsat band radiometer throughout two growing seasons for corn (Zea mays L.) canopies differing in planting dates, populations, and soil types (Typic Argiaquoll and Udollic Ochraqualf). Agronomic data collected to coincide with the spectral data included leaf area index (LAI), biomass, development stage, and final grain yields. The spectral variable greenness was associated with 76% of the variation in LAI over all treatments. Single observations of LAI or greenness were found to have limited value in predicting corn yields. The proportions of solar radiation intercepted (SRI) by these canopies were estimated using either measured LAI or greenness. Both estimates, when accumulated over the growing season, accounted for approximately 65% of the variation in yields. The Energy Crop Growth (ECG) variable was used to evaluate the daily effects of solar radiation, temperature, and moisture stress on corn yields. Coefficients of determination for grain yields were 0.67 for the ECG model using measured LAI to estimate SRI, and 0.68 for the ECG model using greenness to estimate SRI. We conclude that this concept of estimating intercepted solar radiation using spectral data represents a viable approach for merging spectral and meteorological data in crop yield models. The concept appears to be extendable to large areas by using Landsat MSS data along with daily meteorological data and could form the basis for a future crop production forecasting system.
Leaf and Stem Forage Quality of Big Bluestem and Switchgrass1
Authors: Griffin J. L. , Jung G. A. 
Published: July 2010

AbstractA balanced forage program should include species that provide the highest yields of quality forage throughout the grazing period. In the Northeast, where cool‐season grasses predominate, the short supply of forage during summer limits beef cow‐calf herd size. Warm‐season (C4) perennial grasses are productive in midsummer and may supplement temperate species for grazing and hay. ‘NY 1145’ big bluestem (Andropogon gerardi Vitman) and ‘Blackwell’ switchgrass (Panicum virgatum L.) were grown on soils (Aeric Fragiaquualt and Aquic Hapludalf) low in available P at two locations in Pennsylvania to characterize changes in quality of leaf and stem tissue associated with maturation. Forage was harvested at 10‐day intervals beginning at the 3‐ to 4‐leaf stage in late June and continuing until seed set in early August. Percentage leaf tissue declined similarly with maturation for the two grasses. Leaf dry matter yields were approximately twice those of stems in June but the opposite was true in August. At early head emergence, percentage leaf tissue for big bluestem and switchgrass averaged 34 and 44%, respectively. Averaged over grasses, leaf and stem forage quality estimates at early head emergence, respectively, were: crude protein (CP), 9.7, 4.3% in vitro dry matter disappearance (IVDMD), 60.4, 50.0%; neutral detergent fiber (NDF), 66.0, 75.3%; lignin, 4.7, 7.2%; and phosphorus (P), 0.20, 0.16%. Big bluestem leaves were higher in CP but lower in NDF than switchgrass leaves. Stem tissue of big bluestem was lower in NDF but higher in lignin than that of switchgrass. The decline in leaf and stem CP, IVDMD, and P with maturation was less pronounced in leaf tissue. The increase in NDF and lignin with maturity was greater in stems than in leaves. Fiber accumulation in stem tissue continued after seedheads emerged and was accompanied by decreases in CP and IVDMD. At early vegetative stages, the high percentage of good quality leaf tissue suggest the potential use of big bluestem and switchgrass for ruminants with above maintenance energy requirements. However, at later growth stages (late joint early head), the increase in stem tissue and associated decline in nutritive value suggest using these grasses either for grazing or hay by ruminants to meet only maintenance energy needs.
Corn Growth Response to Temperature and Photoperiod II. Leaf‐Initiation and Leaf‐Appearance Rates1
Authors: Warrington I. J. , Kanemasu E. T. 
Published: July 2010

AbstractThe prediction of evapotranspiration and canopy photosynthesis, for example in crop simulation modeling and in remote sensing applications, requires a quantitative description of the influence of environmental factors such as temperature and photoperiod on leaf area development. The objectives of this study were to define the temperature response curves and the responses to photoperiod for two components of leaf area development in corn (Zea mays L.), namely leaf‐initiation rate and leaf‐appearance rate. Plants of two corn hybrids, W346 and XL45, were grown in controlled environments under 17 day/night temperature regimes ranging from 16/6 to 38/33°C (12 h photoperiod) and under three photoperiod regimes (12, 14, and 16 h) at two selected temperatures (constant 18 and 28°C). Leaf‐initiation rates, determined from frequent dissections, were constant from seedling emergence until tassel initiation in all treatments. Similarly the appearance rate of the first 12 leaves was constant from seedling emergence onward, but after leaf 12, appearance rate increased, presumably as a consequence of rapid stem elongation and because the upper stem leaves were smaller and required less time to expand. Both cultivars had similar leaf‐initiation and leaf‐appearance rates under each day/night temperature regime. Data from the day/night temperature regimes were used to derive rate of leaf‐initiation (leaf primordia/day) vs. temperature and rate of leaf‐appearance (leaves/day) vs. temperature response curves which could be described by third and fourth‐degree polynomial equations, respectively. Previously published values for leaf‐appearance rates have varied by up to three or four‐fold at any particular temperature, primarily because of different definitions that have been used for appearance rate. Values for the rate of change in leaf appearance rate with temperature within the 16 to 26°C range, however, were more similar ranging from 0.21 to 0.30 leaves day−1°C−1 and were similar to a value of 0.23 leaves day−1°C−1 obtained in this study. Both leaf‐initiation and leaf‐appearance rates increased with an increase in photoperiod, particularly under constant 18°C conditions. Cultivar W346 appeared to be more responsive to photoperiod than XL45.
Seeding Rate and Seeding Date Effects on Spring Seeded Small Grain Cultivars1
Authors: Ciha A. J. 
Published: July 2010

AbstractOver the past 15 to 25 years the plant characteristics of small grains have changed; however, little is known in the Pacific Northwest about the production practices necessary to maximize grain yields with these short statured, early maturing, lodging resistant small grain cultivars. A 4‐year (1977 to 1980) field study at Pullman, Wash. on a Palouse silt loam (fine‐silty, mixed, mesic pachic Ultic Haploxerolls) examined grain yield and test weight responses to three seeding dates (early, normal, and late) and three seeding rates (40, 75, and 110 kg/ha). Five spring barley (Hordeum vulgare L.), three spring oats (Avena sativa L.), and five spring wheat (Triticum aestivum L.) cultivars were tested. Significant cultivar × seeding date and cultivar × seeding date × year interactions existed for grain yield. Seeding date delays past the normal date significantly reduced grain yield and test weight for the majority of the cultivars when averaged over the 4‐year period. However, several cultivars showed yield reductions with seeding date delays past the earliest date. Several cultivars showed yield reductions with the lowest or highest seeding rate. Reduced yields with the 110 kg/ha seeding rate were caused by lodging. The non‐significant seeding rate × seeding date and cultivar × seeding rate × seeding date interactions for yield indicate that increasing the seeding rate with later seeding dates was not beneficial in increasing grain yield. Test weight values for the small grains averaged over years were generally reduced with late seeding dates.
Alfalfa Stem and Leaf Growth during Water Stress1
Authors: Brown P. W. , Tanner C. B. 
Published: July 2010

AbstractAlfalfa (Medicago sativa L.) requires irrigation in semiarid and arid regions and improved yields often result from irrigation in subhumid and humid areas. Despite the importance of optimizing water management for alfalfa leaf and stem growth, no field study has been reported which relates alfalfa leaf expansion or stem extension to plant water deficits. The objective of our research was to determine how leaf expansion, stem elongation, and stomatal response of alfalfa related to the water potential in alfalfa, field‐grown on Plainfield loamy sand (mixed, mesic Typic Udipsamment). Periodic measurements of alfalfa stem extension and leaf expansion (area derived from length and width measurements) were related to leaf water potential (ΨL) measured with a pressure chamber, soil matric potential (Ψm, measured with tensiometers, and stomatal conductance measured with porometers. For wellwatered alfalfa, expansion curves of individual leaves were sigmoid‐shaped, while internode extensions were nearly exponential with time through about 95% of the total extension. The primary leaf attached at the top of an internode expands to nearly full size before the internode begins rapid extension. The growth of individual leaves and internodes collectively results in nearly constant rates of leaf expansion and stem extension during vegetative regrowth. When Ψm at 30 cm decreased to −0.35 bar, afternoon ΨL decreased to about −8 bars, about 2 bars below irrigated alfalfa, and both the growth rate (GR) and relative growth rate (RGR) of stressed leaves and stems were significantly less (p < 0.1) than well‐watered leaves and stems. In stressed treatments, wilting, gray‐green canopy color, decreased afternoon stomatal conductance, and a 50% decrease in RGR as compared to irrigated treatments resulted when afternoon ΨL decreased to about −15 bars even though Ψm exceeded −0.1 bar at 90 and 150 cm. Alfalfa extracted 85% of its total water from the 1st meter of soil prior to the onset of decreased afternoon stomatal conductance, but nearly equal percentages from each of the top 2 m of soil afterward. Little shoot growth occurred when ΨL dropped below −10 bars. Development of water stress 2 weeks after cutting reduced alfalfa leaf size, internode length, and dry matter production, but not leaf and internode number or stem density. The percentage of total forage dry weight in leaves (LPDW) decreased linearly with stem height resulting in higher LPDW and a better quality forage in stress‐stunted forage. Cool night temperatures limited growth of well‐watered alfalfa.
Steer Performance and Association of Acremonium coenophialum Fungal Endophyte on Tall Fescue Pasture1
Authors: Hoveland C. S. , Schmidt S. P. , King C. C. , Odom J. W. , Clark E. M. , McGuire J. A. , Smith L. A. , Grimes H. W. , Holliman J. L. 
Published: July 2010

AbstractPoor animal performance on tall fescue (Festuca arundinacea Schreb.) pasture may be associated with toxic products produced by the fungal endophyte Acremonium coenophialum Morgan‐Jones and Gams (previously identified and referred to as Epichloe typhina (Fries) Tulasne). The object of this study was to determine steer performance on ‘Kentucky 31’ tall fescue pastures which were either heavily infested or relatively free of the fungal endophyte. Replicated 1.2 ha paddocks were located in west central Alabama on three soils, Sumter clay (fine silty, carbonatic, thermic Rendolic Eutrochrept), Houston clay (very fine montmorillonitic, thermic Typic Chromudert), and Eutaw clay (very fine, montmorillonitic, thermic Entic Pelluderts). They were fertilized annually with 224 kg N ha−1 and grazed with yearling steers. The grazing season during the 4‐year period averaged from 23 October to 24 December and 26 February to 16 June. Tall fescue, averaging 94% of plants fungus infested, produced 768 animal days ha−1 and produced 384 kg beef ha−1 with an average daily gain (ADG) of 0.50 kg. Tall fescue with less than 5% of plants infested produced 593 animal days ha−1 and produced 492 kg beef ha−1, with an ADG of 0.83 kg. Rectal temperatures were 0.8 °C higher and hair coats much rougher on steers which grazed fungus‐infected grass rather than grass free of the fungus. Results of the study furnish further evidence that the fungal endophyte, A. coenophialum, is associated with low performance of steers on tall fescue pasture. In the absence of the fungal endophyte, ADG of steers on tall fescue is high and similar to that on small grain pastures.