bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Exchange of Field‐Grown Soybean under Drought1
Authors: Cortes P. M. , Sinclair T. R. 
Published: July 2010

AbstractDrought stress has been shown to reduce leaf carbon exchange rates (CER) and to hasten leaf senescence of plants. This study was undertaken to assess concurrently the relative effects of each process on seasonal accumulation of C for soybean [Glycine max(L.) Merr.| grown under field conditions. Leaflet CER and water vapor exchange rates were measured continuously during drought stress treatments of two indeterminate cultivars. The cultivars differed in maturity with ‘Wilkin’ being in maturity group 0 and ‘SRF 150’ being maturity group I. Gas exchange measurements were made using an open system with assimilation chambers enclosing uppermost fully expanded leaflets. Data were recorded concurrently every 12 min for leaflets attached to plants in an irrigated treatment and in treatments drought stressed at differing stages of reproductive growth. As a result of drought during reproductive growth, CER of both cultivars was reduced by approximately 25% for the remainder of the season. Drought during flowering to mid‐podfill did not seem to hasten leaf senescence in either cultivar. However, drought after mid‐podfill resulted in a 5 to 10 day earlier leaf senescence of these leaves at the top nodes of the plants. These data suggest that reduced CER for the remainder of the season was a consistent consequence of drought stress during reproductive growth. Hastened leaf senescence could further reduce total accumulated C if drought occurred late in reproductive growth.
Phosphorus‐induced Zinc Deficiency in Wheat on Residual Phosphorus Plots1
Authors: Singh J. P. , Karamanos R. E. , Stewart J. W. B. 
Published: July 2010

AbstractOne‐time heavy application of P on certain soils can provide sufficient available P to sustain crop production over a period of several years, but may cause Zn nutritional problem for crops. A field study was conducted to determine the effect of applied Zn on wheat (Triticum aestivum L.) grown on residual P plots and identify the mechanism of P ✕ Zn interaction. This study was conducted in 1984 in a continuous wheat system on a clayey, mixed, frigid Typic Hyploboroll soil that had received 0, 80, and 160 kg P ha−1 in 1979. Three experiments were carried out using a split plot randomized complete block design with three levels of P as main plots and rates of soilapplied Zn‐sulfate (0, 5, 10, and 20 kg Zn ha−1) or Zn‐chelate (0, 0.5, 1.0, and 2.0 kg Zn ha−1) or foliar‐applied Zn‐chelate (0 and 0.35 kg Zn ha−1) as subplots. A one‐time application of 80 or 160 kg P ha−1 increased wheat yield significantly. In the presence of P, application of Zn resulted in significant increase in grain yield and Zn uptake into grain. Applied P increased soil P levels and tissue P concentration, but resulted in a significant decrease of tissue Zn levels. DTPA (diethylenetriaminepentaacetic acid)–extractable soil Zn levels in the non–Zn‐amended treatment were independent of P application rate. Plant roots in high P treatments contained significantly lower levels of vesicular‐arbuscular mycorrhizal (VAM) infection than the control. Further, a close relationship was observed between Zn levels in the aboveground plant parts and VAM infection.
Ground Cover and Weathering Effects on Reflectances of Three Crop Residues1
Authors: Wanjura D. F. , Bilbro J. D. 
Published: July 2010

AbstractCrop residue, which is important in protecting soil from wind and water erosion, is not easily differentiated from bare soil and difficult to quantify using remote sensing techniques. A field study was conducted on Amarillo fine sandy loam (Aridic Paleustalfs) for the purpose of measuring the change in spectral reflectance due to varying concentrations and weathering of Texas panicum (Panicum texanum Buckl.) pearl millet [Pennisetum americanum (L.) K. Schum], and cotton (Gossypium hirsutum L.) bur residue. Reflectance was measured in seven wavelength intervals with a multiband radiometer (MMR). The greatest change in reflectance occurred between bare soil and 33% ground cover. Band MMR 2 gave the best separation between the crop residues. The MMR bands 1, 2, and 3 provided the best discrimination among fresh residue types; however, as weathering progressed after 240 mm of rainfall, reflectance in bands MMR 5, 6, and 7 was significantly different among residues. The ratio of MMR 5 divided by MMR 6 was < 1.0 for fresh crop residues compared with values > 1.0 after exposure to a 240‐mm rainfall. The largest relative change in reflectance during the weathering period among residues in decreasing order was pearl millet, Texas panicum, and cotton burs. Band MMR 4 showed the greatest relative reflectance change during 251 days of weathering. Detecting crop residue on bare soil with remote sensing techniques may be feasible if it is known whether the residue is fresh or weathered.
Continuous Flow System for Collecting Volatile Ammonia and Amines from Senescing Winter Wheat1
Authors: O'Deen W. A. , Porter L. K. 
Published: July 2010

AbstractEvolution of ammonia and amines from wheat‐media systems following anthesis has previously been observed with chambers that have been either closed or open, but lacking in low ultimate relative humidity. Few systems have isolated the aerial parts of the wheat (Triticum aestivum L.) from its growth medium. Therefore, a freeflow open system was designed that isolated the aerial wheat from its growth medium and obtained low ultimate relative humidities of 10 to 20%. Surfaces of 0.1 M HCl were used to trap the ammonia and amines both inside and outside the chamber, increasing the efficiency of collection. Potted winter wheat was heavily fertilized with five additions of 50 mg N kg−1 soil and watered to near field capacity as required. Emission of volatile bases yielded a sensitive double‐peaked senescent N band. The 90‐day average plant emission of 1.8 mg N m−2 day−1 represented a crop loss of 1.6 kg N ha−1 and 3.1% of the total N in the plant material contained in the chamber.
Techniques for Measuring Intercepted and Absorbed Photosynthetically Active Radiation in Corn Canopies1
Authors: Gallo K. P. , Daughtry C. S. T. 
Published: July 2010

AbstractA portable system that would enable rapid measurement of photosynthetically active radiation (PAR) would be useful in studies that include measurements of interception and absorption of PAR in crop canopies. The objectives of this study were to develop and evaluate a portable system for measuring intercepted and absorbed PAR in corn (Zea mays L.) canopies. This study consisted of two field experiments with corn planted in north‐south rows at two densities with two planting dates in each of 2 yr. The soil was a dark (10YR 4/1) Chalmers silt loam (Typic Argiaquoll). A handle, two levels, and a data logger were added to a line quantum sensor to form a portable system for rapidly measuring the ascending and descending fluxes associated with absorbed PAR (APAR). The effects of sensor orientation and surface length on measurement of transmitted PAR and the errors induced by use of intercepted PAR as an estimate of absorbed PAR were examined. Transmitted PAR (TPAR) was optimally measured with the sensor leveled and positioned perpendicular to the row direction with the length of the sensor equal to the row spacing. Intercepted PAR (IPAR), the difference in descending PAR fluxes above and below the canopy, required fewer measurements than APAR and differed from APAR by the difference between canopy and soil surface reflectances. Prior to the dent stage (R5) of grain maturity, differences between APAR and IPAR were less than 3.5% for this study. Thus IPAR was a reasonable approximation of APAR and required fewer measurements.
Winter Survival Response of Winter Wheat: Tillage and Cultivar Selection1
Authors: Cox D. J. , Larsen J. K. , Brun L. J. 
Published: July 2010

AbstractWinter wheat (Triticum aestivum L.) production in the Northern Great Plains is dependent upon adequate survival of the crown tissue for regeneration of root and shoot in early spring. Thus, the establishment of winter wheat as a viable alternative crop in North Dakota has been dependent upon the use of management practices that enhance winter survival. Objectives of this study were (i) to verify previous results associating winter injury or lack of with tillage and its associated effects on snow depth and soil temperature, and (ii) to determine the affect of tillage and cultivar selection on grain yield in an environment where winter injury frequently is experienced. Two hard red winter wheat cultivars were planted during the fall of 1981 and 1982 into conventional tillage (CT), mulch tillage (MT), and notillage (NT) plots on a Fargo clay (fine, montmorillonitic, frigid Vertic Haplaquoll) located at Fargo, ND. The experiment was repeated during the winters of 1983–1984 and 1984–1985 using MT, and short (0.05 m) and tall (0.20 m) stubble NT plots. Snow depth was greatest in conjunction with tall stubble (0.20 m) and resulted in warmer soil temperatures and a reduction in the duration of time temperatures dropped within the range responsible for winter injury. Winter injury was recorded only for the winters of 1981–1982 and 1984–1985. Percentage winter survival was greatest for NT wheat planted into tall stubble. The survival of MT wheat was intermediate between that of CT and NT wheat. The snow trapping ability of short stubble (0.05 m) and amount of winter injury recorded was similar to that for MT. The mean grain yield of CT, MT, and NT (both 0.05 and 0.20 m) wheat was 455, 2203, 2270 and 4073 kg ha−1 respectively, for the two winters in which winter injury was recorded. There were no significant differences in yield harvested from tillage treatments for the two mild winters. Tillage selection (CT vs. NT) was more important in explaining the variation in percentage winter survival than was cultivar selection.
Yield and Regrowth Characteristics of Alfalfa Grazed with Sheep. II. Summer Grazing1
Authors: Allen V. G. , Hamilton L. A. , Wolf D. D. , Fontenot J. P. , Terrill T. H. , Notter D. R. 
Published: July 2010

AbstractGrazing alfalfa (Medicago sativa L.) in summer would provide high quality forage during periods of low rainfall when other forages are in short supply. ‘Arc’ alfalfa, grown on fine‐loamy, mixed, mesic Fluventic Dystrochrept at Blacksburg, VA, was grazed by sheep following two hay cuts in 1982 and 1983 with six treatments: (i) no grazing with hay being cut at 1/10 bloom; (ii), (iii), and (iv) grazing began approximately 14 days after second hay cut and continued for 2, 4, and 6 weeks, respectively; (v) grazing began at early bud stage and continued for 10 days in 1982 and 7 days in 1983; and (vi) grazing began at early bloom and continued for 7 days. Following grazing, hay was cut on each treatment if regrowth reached 1/10 bloom stage before killing frost. No grazing was imposed in 1984 and hay was harvested three times from plots from all six treatments. Forage remaining after grazing for 2, 4, or 6 weeks was higher in percent leaf, in vitro dry matter digestibility, crude protein, Ca, Mg, and P concentration, and was lower in cell wall constituents than after grazing at early bud or bloom. Grazing for 4 and 6 weeks precluded fall hay harvest and increased weeds. Alfalfa yield in 1984 was reduced by grazing except grazing at early bloom. Yield was 8.5, 7.3, 7.1, 6.7, 7.3, and 8.7 Mg ha−1 for the six treatments, respectively. Weed encroachment generally increased with increased grazing duration (GD). Grazing could decrease productivity, especially as GD is lengthened, but may be less detrimental than previously supposed.
Grazing Duration Effects on Wheat Growth and Grain Yield1
Authors: Winter S. R. , Thompson E. K. 
Published: July 2010

AbstractWinter wheat (Triticum aestivum L.) is frequently grazed from November until March in the Southern Great Plains. The effects of grazing on growth and grain yield are not clearly understood. Irrigated grazing trials were conducted on Pullman clay loam, a fine, mixed, thermic Torrertic Paleustolls soil, to determine the growth and grain yield responses of a semidwarf winter wheat cultivar (TAM 105) planted in late August using five dates of grazing termination in the spring. An ungrazed (grain‐only) treatment that was planted in early October and managed for high grain yield was included for reference. Wheat forage was removed to a 50‐ to 70‐mm stubble height (15 to 30% ground cover) by stocker cattle (Bos taurus L.). Growing conditions were good, and heading dates averaged near normal. Growth and grain yield responses to grazing duration were basically the same for all growing seasons. Three‐year‐average grain yields were 4.79,4.79,4.29,3.70,3.20, and 2.40 Mg ha−1 dry weight for grain‐only, 1 February, 6 March, 17 March, 31 March, and 13 April grazing termination dates, respectively. The wheat grazed until 1 February had reduced leaf area index (LAI), biomass, mean tiller weight, height, and single‐seed weight; but grain yield, tiller density at heading, and harvest index were not reduced when compared to the grain‐only wheat. Grazing until 6 March or later progressively reduced LAI, biomass, tiller weight, height, and single‐seed weight. Heading was delayed by late grazing. Tiller density and harvest index were not reduced unless grazing continued past 31 March and 17 March, respectively. Grazing until 6 March or later appeared to reduce grain yield by limiting LAI and biomass in the spring. Since grain yield was reduced even by grazing until 6 March and the wheat did not reach Feeke's stage 6 until about 1 April, removal of spikes by grazing cattle can not be a primary cause of the loss in wheat grain yield. It was observed that grazing past the period of initial elongation of the first internode delayed internode elongation. This delay in reproductive development caused by continued grazing will need to be considered if grazing termination decisions are based on stage of development.
Environmental × Genotype Effects on Seed Dormancy and After‐Ripening in Wheat1
Authors: Hagemann M. G. , Ciha A. J. 
Published: July 2010

AbstractThe length of the after‐ripening period (ARP) for winter wheat (Triticum aestivum L.) in the Pacific Northwest of the United States is very important. If the ARP is too long, fall planted seeds will not germinate uniformly, resulting in poor stands; preharvest sprouting may occur if the ARP is too short. The objective of this study was to examine the influence of cultivar and temperature during grain fill on the level of seed dormancy during ARP. Three winter wheat cultivars differing in susceptibility to preharvest sprouting were grown in five environments with varying rainfall and temperature conditions during grain fill. Grains were harvested at harvest ripeness and stored at −10, 10, 20, and 30°C during an 8‐week ARP. The level of seed dormancy was calculated using germination index and percent germination values determined at harvest ripeness and after an 8‐week ARP. Seed dormancy at harvest ripeness was a function of cultivar and environment during grain development. Loss of seed dormancy during after‐ripening was a function of the cultivar, the environment in which the grain developed, and the after‐ripening environment. Grains that developed in cool environments generally lost their dormancy more rapidly than grains that developed in warm environments. High temperatures during the ARP generally accelerated the loss of seed dormancy. One of the cultivars with low dormancy at harvest ripeness expressed higher levels of seed dormancy when stored at –10°C for 8 weeks than when it developed under certain field conditions. Environmental conditions typical of the Pacific Northwest, cool temperatures during grain development followed by high temperatures after harvest ripeness of the seed, are conducive to rapid loss of seed dormancy, which may lead to severe preharvest sprouting if grain harvest is delayed.
Corn Seedling Root Growth as Influenced by Soil Physical Properties1
Authors: Logsdon S. D. , Reneau R. B. , Parker J. C. 
Published: July 2010

AbstractManagement practices often affect soil physical properties adversely thus reducing root growth. In the field difficulty arises in determining which soil physical property is influencing root growth because the factors are not readily separated. The purpose of this study was to examine the effects of isolated soil physical factors on corn (Zea mays L.) seedling growth under controlled conditions. Corn was grown in A horizon material of Groseclose silt loam (clayey, mixed, mesic Typic Hapludult) at four bulk densities (1.10, 1.22, 1.35, and 1.47 Mg/m3), four lower soil moisture levels (0.24, 0.21, 0.18, and 0.15 m3/m3), four higher soil moisture levels (0.24, 0.27, 0.30, and 0.33 m3/m3), and three temperatures (25, 21, and 17°C) in growth chamber experiments. Optimal conditions as indicated by maximum root elongation for corn in Groseclose silt loam occurred with volumetric moisture contents from 0.24 to 0.27 m3/m3, bulk densities <1.22 Mg/m3, and a temperature of approximately 25°C. High bulk density, oxygen stress, low temperature, and water stress all reduced root elongation to some extent. Low temperature had the most dramatic effect. At 6 days corn root length at 21°C was only about 20% of that at 25°C, whereas root length at 17°C was only about 5% of that at 25°C. As bulk density increased, root length decreased. After 4 days high soil moisture stimulated root growth. Root length was not reduced by low soil moisture except at the lowest level (equivalent to a matric potential of −1090 kPa).
Quality Analysis of Summer‐Annual Forages. II. Effects of Forage Carbohydrate Constituents on Silage Fermentation1
Authors: Fisher D. S. , Burns J. C. 
Published: July 2010

AbstractFermentation characteristics of many of the sorghum (Sorghum bicolor L.) types and cultivars within types and the consequent relationship between nonstructural carbohydrates and fermentation products of such forages has not been adequately examined. The objectives of this study were to examine fermentation products and changes in nonstructural carbohydrate fractions with ensiling and relate these to the unfermented forage characteristics of one millet (Pennisetum americanum L.), one corn (Zea mays L.), and eight sorghum cultivars. The buffering capacity of unfermented forage was found to be greater (P<0.01) in sorghum (9.8 mL 0.1 M lactate) than in corn (8.0 mL 0.1 M lactate). Starch was less susceptible to degradation during fermentation than sugar. High levels of starch resulted in fermentation and loss of a smaller proportion of the total nonstructural carbohydrates (TNC). Reductions in TNC ranged from 61 g kg−1 for ‘Tifleaf‐I’ millet to 239 g kg−1 for ‘NK‐367’ forage sorghum at Location 1 and 30 g kg−1 for ‘Savanna‐5’ grain sorghum to 167 g kg−1 for NK‐367 forage sorghum at Location 2. Predictive equations for the proportion of TNC retained after ensiling were developed using unfermented forage characteristics as independent variables. These regression equations accounted for 70 to 91% of the variation. By weight, the most important fermentation products were lactate (42.9–114.1 g kg−1), acetate (9.4–39.4 g kg−1), and ethanol (1.4–50.0 g kg−1). Only small quantities of substrate were fermented to propionate (0.0–1.3 g kg−1), butyrate (0.3–1.6 g kg−1), and acetaldehyde (0.4–1.3 g kg−1). Palatability was positively correlated with acetate (r=0.70*), propionate (r=0.91**), and total sugars in the silage (r=0.84**).
Radiation Balance of Dryland Grain Sorghum as Affected by Planting Geometry1
Authors: Steiner J. L. 
Published: July 2010

AbstractThe effects of planting geometry on the radiation balance of dryland grain sorghum (Sorghum bicolor L. cv. DK 46) were studied in a field experiment at the USDA‐ARS Conservation and Production Research Laboratory at Bushland, TX, in 1984 on a Pullman clay loam (a fine, mixed, thermic Torrertic Paleustoll). The objective was to reduce the radiation load on a crop through manipulation of planting geometry and to determine whether that would affect crop productivity. Net radiation was 5% higher over wide compared to narrow rows (0.76 and 0.38 m, respectively) when averaged over three population levels from 33 to 110 days after sowing. East‐west rows had 14% higher net radiation than north‐south rows, averaged over two row spacings. The differences in net radiation were due to daytime responses, presumably shortwave albedo differences. Leaf photosynthesis and transpiration rates and stomatal resistance were measured twice during the grain‐filling period. These measurements, taken 5 days after a period of moderate rains, showed no differences in the plant response due to row spacing or direction treatments. Slightly higher leaf temperatures in the high‐population plots may have been related to greater depletion of plant available water than in medium and low population plots (72, 66, and 67% depletion, respectively). After 2 weeks of drying, narrow‐row and high‐population treatments showed greater stress as evidenced by lower transpiration and photosynthesis rates and higher stomatal resistance and leaf temperature. Soil water depletion was 20% less in narrow than wide rows during a 2‐week period spanning the leaf transpiration measurement dates. Leaf photosynthesis, transpiration, temperature, and stomatal resistance were not affected by differences in net radiation due to row spacing or row direction.
Nitrogen Fixation and Translocation in Field‐Grown Fababean1
Authors: Zapata F. , Danso F. , Hardarson G. , Fried M. 
Published: July 2010

AbstractFababean (Vicia faba L. var. minor) has high N requirements for optimum yields. There are some indications that this legume can satisfy a greater part of this requirement largely through biological N2 fixation. To confirm these observations, more quantitative estimates of N2 fixed in fababean on different soils and over different seasons are necessary. Also, detailed N nutrition and translocation studies could serve as the basis for any required improvement in N2 fixation. This study assessed the contribution of soil, fertilizer, and fixed N2 to the nutrition and growth of fababean at seven growth stages. The soil used is classified as a Typic Eutrocrept. The A‐value approach, involving the application of 20 and 100 kg N/ha of l5N‐labeled ammonium sulphate to fababean and spring wheat (Triticum vulgare) as a reference crop, respectively, was used to assess the relative contributions of N from fixation, soil, and fertilizer to plant growth. At physiological maturity harvest (126 days after planting), fababean had accumulated 209 kg N/ha, 79% of which was derived from fixation, with about 20% coming from soil and 1% from the labeled fertilizer. These results confirm that fababean has the ability for high N2 fixation. Growth and N2 fixation were, however, low during early growth (0–59 days after planting), but increased rapidly after this period. The maximum N2 fixation rate was achieved between the early and mid‐pod‐filling stages, an interval during which N2 fixation accounted for more than 4 kg N/ha/day. The N2 fixation activity dropped to almost zero after the mid‐podfilling stage. After the mid‐pod‐filling stage, the N demand of the developing seeds and pods was higher than could be satisfied through the negligible soil uptake of N and N2 fixation. Thus, N translocated from the shoot was virtually the only source for pod and seed development at these final stages. With such a high level of N2 fixation in fababean, it was estimated that after grain removal, fababean growth led to a net positive residual N level in soil.