bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soil Temperature Limitation to Water Use by Field‐Grown Winter Wheat
Authors: Wraith J. M. , Ferguson A. H. 
Published: July 2010

AbstractModification of crop water use patterns in response to the field soil temperature regime has important agronomic and environmental implications. A 2‐yr field study was conducted to ascertain how soil temperature modification influenced seasonal soil water depletion for a winter wheat (Triticum aestivum L.) crop near Bozeman, MT. Soil surface cover materials including clear plastic, white metal, and styrofoam were applied in the fall after germination and plant establishment. Soil temperature and water content profiles were monitored throughout the winter and spring growing seasons. Soil water depletion was significantly accelerated for those treatments having relatively warmer soil temperatures. Differences of up to 65 mm of cumulative soil water depletion were observed between warm and cool treatments during spring. Significant water extraction from a given depth within the soil profile did not occur until the soil temperature reached 10 to 11 °C during 1985. Repeated rainfall during 1986 obscured any relationship between minimum soil temperature and water uptake in the upper soil profile, but the same relationship as during 1985 was noted at greater depths. Although the nature of our field data does not allow determination of whether cold temperatures constrained root growth, root water uptake, or both of these processes, our field results substantiate conclusions drawn by other investigators using controlled‐environment techniques. It is clear that cultural practices or climatic changes affecting seasonal soil temperature can impact soil water utilization by winter wheat in thermally limited growing areas.
Plot Techniques for Assessment of Bunch Weight in Banana Trials under Two Systems of Crop Management
Authors: Ortiz Rodomiro 
Published: July 2010

AbstractBanana (Musa spp.) is an important perennial crop in tropical countries. Testing improved germplasm and/or agronomic practices to increase productivity requires accuracy and precision. The objectives of this study were to determine the optimum plot size (i.e., number of plants per experimental plot) and the number of replications to detect significant true mean differences in bunch weight (i.e., commercial yield) between treatments. Three uniformity trials of the cultivar Valery grown in Ultisols under two different management practices (alley cropping of banana with multispecies hedgerows and monocropping of banana in cleared land) and at two locations in the humid forest zone of sub‐Saharan Africa were used. The methods of maximum curvature and comparison of variances were used to determine optimum plot size, while the number of replications was estimated by Hatheway's method. This statistical procedure considered an expected relative magnitude of differences between treatment means at a specific probability level and the relationship between the coefficient of variation and soil heterogeneity. The experimental plot should have a single row of 5 plants for banana in an alley cropping system, whereas single rows of 20 plants plot−1 are required in a monocropping system. This finding indicates that alley cropping of banana with multispecies hedgerows may be an adequate system not only to maintain diversity but also for greater efficiency in testing improved germplasm. A table was developed, indicating the expected detectable true mean differences for bunch weight per plant for different number of treatments tested (5–30), plants per plot (5–40), replications (2–6), and management practices. This table allows musa researchers to select minimum trial sizes, according to their objectives and available resources. For example, when 30 treatments are tested in alley cropping fields, using randomized complete block designs with two replications of 10 plants plot−1, a true bunch weight mean difference of 15% may be found to be significant.
Tillage and Rotation Effects on Corn Yield Response to Fertilizer Nitrogen on Aqualf Soils
Authors: Stecker John A. , Buchholz Darly D. , Hanson Roger G. , Wollenhaupt Nyle C. , McVay Kent A. 
Published: July 2010

AbstractFertilizer N recommendations are often increased for no‐till corn (Zea mays L.) relative to conventionally tilled corn. A comparison of relative yield responses to fertilizer N is lacking for continuous corn and corn following soybean [Glycine max (L.) Merr.] when grown with conventional and no‐tillage systems on poorly drained claypan soils. Field studies spanning 5 site‐years were conducted on somewhat poorly (Udollic Ochraqualf) and poorly (Mollic Albaqualf) drained claypan soils in central and northeast Missouri. The experimental design was a split‐split plot, where whole plots were tillage system (chisel‐disk and no‐till) and subplots were rotation (continuous corn and corn following soybean). Subsubplots were N rates of 0, 67, 135, 202, and 269 kg ha−1, applied preplant as either anhydrous NH3 (82‐0‐0 N‐P‐K) or knife‐injected urea‐ammonium nitrate (UAN) solution (32‐0‐0). Corn grain yield response to fertilizer N was described by quadratic and quadraticplateau models that had similar R2 values. With continuous corn, both models predicted no‐till to require 14 to 17 kg ha−1 (5–7%) less fertilizer N for maximum yield and profit than the chisel‐disk system. The predicted maximum no‐till grain yield was 0.34 Mg ha−1 less than the chisel‐disk system. No‐till corn following soybean required an average additional 17 kg N ha−1 (8%) for maximum yield (quadratic model) and 45 kg N ha−1 (35%) for maximum profit (quadratic‐plateau) than the chisel‐disk system. The average maximum yield for no‐till corn following soybean was 0.20 Mg ha−1 less than the chisel‐disk system. Apparent N credit for corn following soybean varied from 0 to 159 kg ha−1. With the quadratic model, the average N credit was 54 kg ha−1 for the chisel‐disk system and 24 kg ha−1 for no‐till. Decreased no‐till corn yields that required equal or greater fertilizer N indicate at least a short‐term economic disadvantage for this tillage system on these poorly drained soils.
Aerodynamic Characteristics of Corn as Determined by Energy Balance Techniques
Authors: Tolk Judy A. , Howell Terry A. , Steiner Jean L. , Krieg Daniel R. 
Published: July 2010

AbstractAerodynamic resistance to heat transfer (rah) needed to calculate sensible heat flux (H) used in energy balance modeling can be estimated from momentum aerodynamic resistance with corrections for atmospheric stability. This study compared rah and H modeled by four commonly used resistance methods with rah and H measured indirectly through energy balance techniques. Three momentum aerodynamic parameters were calculated: roughness length, Zom; zero plane displacement, d; and friction velocity, U*. Corn (Zea mays L.) was grown on east‐west rows (0.75 m wide) in 1989 and 1990 at Bushland, TX, in two contiguous 5‐ha fields where two weighing lysimeters were located and micrometeorological measurements were made. Sensible heat flux was indirectly measured as a residual of the energy balance and then used to calculate aerodynamic resistance. Momentum aerodynamic parameters were calculated from near‐neutral condition wind‐speed profiles using a least squares procedure. The momentum parameter relationships to crop height (CH) were d = 0.73 ✕ CH (r2 = 0.59) and Zom = 0.12 ✕ CH (r2 = 0.96). While no rah model performed well, the best linear fit (r2 = 0.75, y = 1.08x + 4.2) between measured (x) and modeled (y) rah occurred under stable atmospheric conditions; for measured and modeled H, the best linear fit (r2 = 0.84, y = 0.93x + 62.1) occurred under all atmospheric conditions. Measured rah in neutral and unstable conditions was not closely associated with wind speed. Performance of a model with a limited stability factor was improved by increasing the magnitude of the factor. These results suggest that rah models may be sensitive to atmospheric stability and local conditions such as fetch and leaf area.
Estimating Leaf Wetness in Dry Bean Canopies as a Prerequisite to Evaluating White Mold Disease
Authors: Deshpande Rohini Y. , Hubbard Kenneth G. , Coyne Dermot P. , Steadman James R. , Parkhurst Anne M. 
Published: July 2010

AbstractIn semiarid regions, wetness of leaves or other plant parts is essential for development of white mold disease [caused by Sclerotinia sclerotiorum (Lib.) de Bary] in dry edible bean (Phaseolus vulgaris L.). Our goal was to monitor leaf wetness in field plots and predict leaf wetness from prevailing meteorological conditions. The dew point within the canopy and the adjacent leaf temperature (infrared) were used to estimate leaf wetness in two dry bean cultivars of highly contrasting canopy architecture. These are simple, direct measurements that do not disturb the canopy. Sensors were calibrated before and after field measurement periods. Results were compared with the saturation air vapor pressure deficit from a nearby weather station to derive an empirical equation for estimating leaf wetness. The measured leaf wetness period in the dense canopy (cv. Tara) exceeded that in the open canopy (cv. Starlight) by 14% (plus an offset of 1.35 h). This corresponded to higher white mold disease (WM) severity in the dense than in the open canopy. The respective WM severity for dense and open canopies was 93 and 32% in 1990, and 73 and 10% in 1991. The empirical relationship for estimating hourly leaf wetness explained 81% of the variance in the open canopy and 70% of the variance in the dense canopy in 1991; in 1992, accuracy approached 90%. Thus, nearby weather station data offer input to a method that in turn offers a means of assessing leaf wetness in Tara and Starlight, with potential for use with other cultivars. Theoretical considerations indicate that the empirical coefficients are a function of canopy microclimate. Further studies should evaluate the relationship between these empirical coefficients and canopy architecture.
Comparison of Limited Irrigated vs. Dryland Cropping Systems in the U.S. Great Plains
Authors: Norwood Charles A. 
Published: July 2010

AbstractIrrigated hectares in the Great Plains are being converted to dryland because of the declining water table and increasing energy costs for irrigation. A study was conducted in the central Great Plains near Garden City, KS, from 1989 through 1991 to compare limited‐irrigated cropping systems for use on land that would otherwise be converted to dryland. Irrigated continuous winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] were compared with the wheat‐sorghum‐fallow rotation where either one, both, or neither crop was irrigated. Irrigated wheat yields in the rotations averaged 26% more than dryland. Rainfall eliminated any benefits of irrigation on the 1989 and 1990 grain sorghum, but yields in the rotations were increased an average of 168% over dryland in 1991. Average irrigated continuous wheat and sorghum yields were 19 and 8% less than irrigated rotated wheat and sorghum yields, respectively, in 1990 and 1991, but when yields were annualized continuous wheat and sorghum averaged 20 and 59% more than the irrigated rotations. Annualized irrigated rotation yields were similar to dryland in 1990, but 68% more in 1991. Irrigating either crop in the rotation produced similar annualized yields, but irrigating both crops increased yield an additional 13%. Irrigation water use efficiencies were highest for the rotated crops, and lowest for the continuous crops. More grain can be produced with very limited irrigation than with dryland systems, but no single system is best for all conditions. Producers with less water should probably irrigate fallow systems, while those with more water can crop more intensely.
Yields of Alfalfa Varieties Selected for Aphanomyces Resistance in Kentucky
Authors: Vincelli Paul , Lauriault Leonard M. , Henning Jimmy C. 
Published: July 2010

AbstractField tests were conducted over 4 yr to investigate whether alfalfa (Medicago sativa L.) varieties and experimental populations selected for resistance to aphanomyces root rot (caused by Aphanomyces euteiches Drechsler) (here termed aphanomyces‐selected varieties) would collectively outyield varieties not selected for resistance (unselected varieties). All entries were resistant to phytophthora root rot (caused by Phytophthora medicaginis E.M. Hans & Maxwell). At the conclusion of the tests, the mean cumulative dry matter yield of aphanomyces‐selected varieties was higher (4.2% increase, P = 0.063) than that of unselected varieties in a site naturally infested with A. euteiches and P. medicaginis. However, total yields of certain unselected varieties equaled or even exceeded (P = 0.10) those of certain aphanomyces‐selected varieties, and there was no correlation among varieties between yield and percentage of Aphanomyces‐resistant plants. No significant difference in mean cumulative yield was observed between aphanomyces‐selected and unselected varieties in two sites infested with A. euteiches alone nor in four sites not infested with either pathogen. Since outbreaks of seedling diseases were minor in all tests, the yield effects observed may be due to differences in plant health manifested after stand establishment. Our data are consistent with the hypothesis that selection for Aphanomyces resistance contributes to an overall improvement of elite alfalfa germ plasm for cultivation in poorly drained soils infested with both A. euteiches and P. medicaginis. However, considered alone, selection for Aphanomyces resistance in individual varieties was not always predictive of high yield in Aphanomyces‐infested sites. These tests do not rule out the possibility of a substantial yield benefit to Aphanomyces resistance under conditions unusually conducive to seedling disease induced by A. euteiches.
Distinguishing Resource Competition and Chemical Interference: Overcoming the Methodological Impasse
Authors: Weidenhamer Jeffrey D. 
Published: July 2010

AbstractUnderstanding allelopathy may hold the key to new weed management strategies. However, the difficulty of distinguishing chemical interference from competition has hindered studies of allelopathy in natural and cultivated plant communities. Experimental rigor has increased, but has yet to provide unambiguous proof of allelopathy. The complexities of allelopathic interactions, as illustrated by ongoing investigations in the Florida scrub, make it unlikely that clear examples will be forthcoming. While conclusive proof of chemical interference may not be attainable, the challenge of obtaining strong supportive evidence remains. Progress is needed in bioassay methods that distinguish allelopathy from other interference mechanisms. Phytotoxic effects are density‐dependent in a manner inconsistent with resource competition, suggesting that allelopathy can be distinguished by characteristic growth responses across planting densities. In monoculture, greater phytotoxicity at low plant densities causes deviations from expected yield‐density relationships. In mixed culture, the targetneighbor method, in which differing densities of a neighbor species are planted around a target plant, has been used to study phytotoxic effects. In the presence of an applied phytotoxin, increased growth of sensitive target plants as the density of insensitive neighbors increases is inconsistent with a hypothesis of resource competition and provides compelling, though not conclusive, evidence for chemical interference. Once evidence of allelopathy is obtained from plant growth studies, supportive analytical data must be obtained from analyses of toxin concentrations and flux rates in the soil and rhizosphere. The use of adsorbent materials originally applied to the analysis of organic pollutants should allow the measurement of allelochemical flux rates in addition to static concentrations.
Subsoil Nitrate Uptake and Symbiotic Dinitrogen Fixation by Alfalfa
Authors: Blumenthal Jürg M. , Russelle Michael P. 
Published: July 2010

AbstractAlfalfa (Medicago sativa L.) is a deeply rooted perennial that may be able to remove NO3 from the subsoil beneath the rooting zone of annual crops. Our main objectives were to characterize the potential of two alfalfa cultivars (Agate and Ineffective Agate, an ineffectively nodulated near isoline of Agate) to remove NO3 from the subsoil and to evaluate the influence of available subsoil NO3 on symbiotic N2 fixation. Low (≈0.3 mM) or high (20 mM) NO3−N concentrations were supplied through a subsoil irrigation system installed in a Hubbard loamy sand soil (sandy, mixed Udorthentic Haploboroll) at Becker, MN. Nitrate uptake and N2 fixation were evaluated during two regrowth periods using 15N. During fall regrowth in the establishment year, supply of 20 mM 15N‐enriched NO3 through subsoil irrigation did not decrease symbiotic N2 fixation; during summer regrowth of the first production year, symbiotic N2 fixation decreased only 40% (from 7.77 to 4.60 g N m−2). Even though it had higher yields, Agate alfalfa removed less subsoil NO3−N (1.52 and 5.51 g N−2) than did Ineffective Agate (3.12 and 7.13 g N m−2) in each of two harvests where 15N was applied. Root length and mass after 2 yr were not altered by NO3 treatment or cultivar. This is the first time that direct measurements of subsoil nitrate removal have been made in the field for an N2‐fixing crop. Because it is unlikely that differences in NO3 uptake efficiency could account for such cultivar differences, we propose that assimilation of atmospheric N2 reduced the capacity of the fixing crop to absorb NO3. These results suggest that non‐N2‐fixing alfalfa cultivars would be more useful for bioremediation of nitratecontaminated sites than standard cultivars.
Plant Morphology and Forage Nutritive Value of Three Bahiagrasses as Affected by Harvest Frequency
Authors: Cuomo G. J. , Corkern D. L. , McCoy J. E. , Walz R. , Blouin D. C. 
Published: July 2010

AbstractDifferences in morphological development have been reported among bahiagrass (Paspalum notatum Flügge) cultivars. Relationships of harvest management to these developmental differences and subsequent forage production and nutritive value have not been characterized. A 2‐yr study was initiated by harvesting ‘Argentine’, ‘Pensacola’, and ‘Tifton 9’ bahiagrass every 20, 30, or 40 d from mid‐May until mid‐September. Objectives were to determine if differences exist among these cultivars for leafiness, morphological development, forage mass, and forage nutritive value, and to determine if differences were affected by harvest frequency and season of growth. Leaf percentage by weight, inflorescence development, forage nutritive value, and forage mass were evaluated for monocultures of the three cultivars. Argentine had a greater (P 0.01) percent leaf (87.2%) than did Pensacola (80.4%) or Tifton 9 (81.0%). In addition, Argentine and Tifton 9 produced fewer (P = 0.01) inflorescences at 20‐ and 30‐d harvest frequencies than did Pensacola. Leaf percentage was greater (P = 0.01) at 20‐ (88.7%) than at 30‐ (78.6%) and 40‐d (81.4%) harvest frequencies. There were cultivar × plant part interactions (P < 0.05) for neutral detergent fiber (NDF) and lignin, but differences were detected only in the stem component. No differences (P ≤ 0.05) were detected among cultivars for other nutritive value variables. Total forage mass was similar (P ≤ 0.05) among cultivars. Differences in forage mass were detected (P = 0.01) only at the first harvest, where Argentine produced less forage (1.9 Mg ha−1) than Pensacola (3.1 Mg ha−1) or Tifton 9 (2.9 Mg ha−1). The combination of greater leaf percentage and fewer inflorescences indicate that Argentine could have potential advantages as a forage over other bahiagrass cultivars.
Effect of Wheat Morphological Stage at Grazing Termination on Economic Return
Authors: Redmon Larry A. , Krenzer Eugene G. , Bernardo Daniel J. , Horn Gerald W. 
Published: July 2010

AbstractThe economic impact of timing of grazing termination in the wheat (Triticum aestivum L.) grain‐stocker cattle (Bos sp.) enterprise has not been elucidated. A 4‐yr study used the first hollow stem stage of growth in ungrazed wheat as a grazing termination indicator and the subsequent effect on net return. First hollow stem is the stage at which hollow stem can first be identified above the crown; it occurs prior to the growing point reaching the soil surface. Net return was maximized when grazing was terminated at first hollow stem. Grain yield decreased (P< 0.05) 83 kg ha−1 d−1 as cattle grazed past first hollow stem. Increased weight gain by cattle was not sufficient to offset grain yield losses. Since hollow stem formation was delayed in grazed wheat, producers who use semidwarf wheat as a dual‐purpose crop should monitor the morphological stage in ungrazed areas of the field to determine the optimum time to terminate grazing.
NEPER‐Weed: A Picture‐Based Expert System for Weed Identification
Authors: Schulthess Urs , Schroeder Kris , Kamel Ahmed , AbdElGhani AbdElGhani M. , Hassanein El‐Hassanein E. , AbdElHady Shaban Sh. , AbdElShafi AbdElMaboud , Ritchie Joe T. , Ward Richard W. , Sticklen Jon 
Published: July 2010

AbstractMost current expert systems for weed identification are ruled‐based. They use text only and rely on a large number of botanical terms. In rule‐based expert systems, knowledge is not organized in a structured manner. Hence, they are difficult to create and use. This article describes the advantages of the generic task approach to building expert systems. The generic task approach is based on the assumption that certain knowledge and control structures may be common to a particular task across domains. Hence, reusable control structures, or tools, have been developed to solve problems. We developed an expert system that uses a hierarchical classification tool. Text descriptions are replaced with pictures, to minimize the use of technical terms. Hypotheses are established or ruled out on the basis of the user's choices among options presented as pictures. This approach reduces the number of characters required for weed identification and the user does not need to know technical terms. In our system, the classification of grasses is based on the morphologies of the leaf base and leaf surface. Broadleaf weed classification is based on the shapes of the cotyledon and true leaf. The system contains 51 Egyptian weeds. The hierarchical classification tool allowed for a clear separation of the knowledge from the structure in which the knowledge is organized. The object‐oriented nature of this approach simplifies adding or removing weeds. This approach can be readily applied to other domains, such as disease identification, fertilizer recommendation, or cultivar selection.
Soybean Physiology, Regrowth, and Senescence in Response to Defoliation
Authors: Klubertanz Tom H. , Pedigo Larry P. , Carlson Richard E. 
Published: July 2010

AbstractRecent studies have shown that one component of soybean [Glycine max (L.) Merr.] response to insect defoliation is delayed senescence and increased physiological activity of lower, remaining leaves. The objective of this study was to test the ability of these and other mechanisms of defoliation tolerance to function in drought‐stressed plants. Controlled irrigation rates and artificial defoliation treatments were used in a 2‐yr study. Defoliation significantly increased soil‐moisture percentage in both years, showing that defoliated stressed plants conserve more water than nondefoliated stressed plants. Compensatory regrowth was observed following defoliation, resulting in more leaves in defoliated plants than predicted. Removal of expanding leaves, however, reduced leaf area and also reduced growth potential relative to nondefoliated plants. Senescence of lower leaves was delayed in defoliated plants, as has been found in previous studies. The responses of leaf physiological rates to defoliation were similar in drought‐stressed and well‐irrigated plots. These data suggest that crop models integrating physiological parameters and defoliation rates could add or subtract the effect of drought stress as a constant or simple function.