bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ammonium and Nitrate Nitrogen in Soil Profiles of Long‐Term Winter Wheat Fertilization Experiments
Authors: Westerman Robert L. , Boman Randal K. , Raun William R. , Johnson Gordon V. 
Published: July 2010

AbstractAccumulation of NH+4 ‐N and NO‐3 ‐N in soils has not been thoroughly evaluated in long‐term continuous winter wheat (Triticum aestivum L.) production systems. The objectives of this study were to determine long‐term response of winter wheat to N fertilization and to evaluate accumulation of NH+4 ‐N and NO‐3 ‐N in the soil profile. Four long‐term winter wheat soil fertility experiments on thermic Ustoll soils that received annual applications of N for > 18 yr at selected N rates were sampled. At each location, one soil core 4.4 cm in diameter was taken to a depth of 240 cm from plots receiving variable N rates. Cores were separated into 30‐cm increments and analyzed for 2 M KCI‐extractable NH+4 ‐N and NO‐3‐N. At all locations, NH+4 ‐N levels were not significantly different from the check (no fertilizer N) when rates were applied at or below yield goal requirements (90 or 45 kg N ha−1 vs. 0 N). At N rates >90 kg N ha−1, surface (0–15 cm) NH+4 ‐N increased compared with the check, while subsurface NH+4 ‐N did not. Similarly, when N rates were <90 kg N ha−1, no significant differences in either surface or subsurface NO‐3 ‐N were found. At N rates >90 kg N ha−1, NO‐3 ‐N accumulated in the subsurface soil profile (>30 cm). Estimates of N rates determined from simultaneous solutions of NO‐3 ‐N accumulation minimums and yield maximums generated from quadratic regression were greater than N rates currently recommended to achieve yield goals at all locations. For these long‐term continuous winter wheat experiments, no accumulation of NH+4‐N and NO‐3 ‐N occurred at recommended N rates where near maximum yields were obtained.
Plasmid Profiles of Rhizobia Used in Inoculants and Isolated from Clover Fields
Authors: Moënne‐Loccoz Yvan , Sen Dipankar , Krause Erica S. , Weaver Richard W. 
Published: July 2010

AbstractThe persistence of inoculant strains of Rhizobium is a factor determining the need for inoculation of legumes. Four pastures in east Texas, with known histories of arrowleaf [Trifolium vesiculosum Savi] and crimson [T. incarnatum L.] clover planting and inoculation with R. leguminosarum bv. trifolii, were used to investigate the prevalence of inoculant strains in clover root nodules. Three pastures had mixed stands of the two clover species, and the fourth had only arrowleaf clover. Using plasmid profiles as a means of identifying rhizobial strains, we analyzed 50 rhizobial isolates made from root nodules of each clover species in each of the pastures. Sixty‐six plasmid profile types were obtained from the 350 isolates. For the first three sites, only 2 of 300 isolates had plasmid profiles matching that of an inoculant strain, and 5 others had profiles similar but not identical to that of another inoculant strain. More than one‐half of the plasmid profile types corresponded to variations of a single type, distinctly different from that of any inoculant strain. At the site where only arrowleaf clover had been grown, 70% of the isolates had a plasmid profile identical to that of an inoculant strain not used at the site. The instability of the plasmid profile of the latter, when grown in vitro, and the similarity of its plasmid and total soluble protein profiles to those of the inoculant strains used at this site, indicate that the prevalent type probably originated from one of them. The inoculant strains failed to persist as such in the field, regardless of the frequency of inoculation.
Allelopathic Characteristics of Three Cool‐Season Grass Species in the Forage Ecosystem
Authors: Smith A. E. , Martin L. D. 
Published: July 2010

AbstractAllelopathy, the direct or indirect effect of one plant on another through the production of chemical compounds that escape into the environment, occurs widely in natural plant communities and is postulated to be one mechanism by which weeds interfere with crop growth. The purpose of this research was to determine the potential allelopathic influence of selected cool‐season grass species on species interseeded into the pasture ecosystem. Aqueous extracts of tall fescue (Festuca arundinacea Schreb.), Italian ryegrass (Lolium multiflorum Lam.), and little barley [Critesion pusillum (Nutt.) A. Löve; syn. Hordeum pusillum Nutt.] leaf and stem tissue harvested at the mature stage of plant development reduced seed germination and seedling growth of alfalfa (Medicago sativa L.) and Italian ryegrass. It was estimated that 2.8 and 2.5 g L−1 aqueous extracts of mature tall fescue stem tissue, resulted in a 50% reduction in alfalfa seed germination and seedling growth, respectively. For the extracts from Italian ryegrass and little barley, it was estimated that tissue concentrations of near 5.0 g L−1 resulted in a 50% reduction in seed germination and seedling growth for the two bioassay species. Leaf and stem tissue concentrations of the three grasses >7.0 g L−1, resulted in complete inhibition of alfalfa seedling growth. The potential concentration for foliage tissue in soil solution of the pasture ecosystem for tall fescue, Italian ryegrass, and little barley would be 28, 23, and 9 g dry wt. L−1, respectively. Therefore, the allelopathic characteristics of these species could be of economic importance in the pasture ecosystem when overseeding the pasture with annual ryegrass or alfalfa.
Effect of Weed Interference and Soil Nitrogen on Four Maize Hybrids
Authors: Tollenaar M. , Nissanka S. P. , Aguilera A. , Weise S. F. , Swanton C. J. 
Published: July 2010

AbstractIn a mixture of crop and weeds, competition exists between plants for incident solar radiation, soil nutrients, and soil moisture. Integrated weed management manipulates cropping‐system factors such that the competitive relationship favors growth of the crop at the expense of the weeds; however, relatively few studies have been reported on the influence of cropping‐system factors on crop‐weed competition. The objectives of this study were to evaluate the impact of weed interference on the performance of four maize (Zea mays L.) hybrids and to examine the influence of soil N level on the competitiveness of the hybrids. Experiments were conducted during 1990, 1991, and 1992 at the Elora Research Station, Elora, ON, on a London loam (Aquic Hapludalf) soil that had been tile drained. Maize hybrids included an old hybrid (Pride 5, released in 1959) and three more recently released hybrids (Pioneer 3902, DEA, and Pioneer 3953). The maize hybrids were grown at 7 plants m−2 under three weed pressures and at two soil N levels. Weed pressures were established by varying the weed‐free period after planting: all season (weed free), planting to 5‐ to 7‐leaf stage of maize (medium weed pressure), and planting to 3‐ to 4‐leaf stage of maize (high weed pressure). Maize dry matter accumulation and grain yield were measured. Mean grain yield of four hybrids across 3 yr was 65% higher in the high‐N, weed‐free treatment than in the low‐N, high‐weed‐pressure treatment. The effect of weed interference on maize grain yield was higher at low than at high N. Maize hybrids responded differently to N level and weed interference; yield of the old hybrid was reduced more by low N and weed interference than yields of the new hybrids. Consequently, selection of maize hybrid and soil N level should be an integral part in the design of a weed management system.
Nitrogen Source, Timing of Application, and Placement: Effects on Winter Wheat Production
Authors: Mahler Robert L. , Koehler Fred E. , Lutcher L. K. 
Published: July 2010

AbstractStudies to increase profitability and N use efficiency in winter wheat (Triticum aestivum L.) production are needed to develop more sustainable agricultural systems in the 480‐ to 650‐mm precipitation zone of northern Idaho and eastern Washington. Field experiments were conducted on Latahco silt loam (fine‐silty, mixed, frigid Argiaquic Xeric Argialboll) soils east of Moscow, ID, during the 1982–1983, 1983–1984, 1985–1986 and 1986–1987 growing seasons. Fifteen different N placement‐source‐application timing treatments were arranged in a randomized complete block design with five replications. Fertilizer placements were (i) surface broadcast, (ii) band 50 mm below the seed, and (iii) combinations of surface broadcast and banded below the seed placements. Times of application treatments were (i) fall, (ii) spring, and (iii) various fall‐spring splits. All treatments were evaluated with two N sources: NH4NO3 (AN) and urea (U). Parameters evaluated were (i) winter wheat stand counts, (ii) early‐season plant biomass, (iii) grain yield, and (iv) apparent N use efficiency (NUE). Placement, N source and time of application had minimal impacts on winter wheat stand counts and early season biomass production. Both winter wheat grain yield and apparent NUE were greatest when N applications were split between fall and spring. Splitting time of N application resulted in apparent NUE of 58 to 61%, compared with 52 to 55% and 51 to 53% for fall only and spring only N applications, respectively. Grain yield and apparent NUE differences attributable to N source and N placement were not significant. Based on this study, ideal N management in the 480‐ to 650‐mm precipitation zone would utilize AN, U, or comparable N sources and split N applications where as little as 25% of the N is banded below the seed or surface broadcast in the fall, with the remainder applied as a spring topdress prior to Zadoks growth stage 24. This proposed management will improve both profitability and water quality by increasing both grain yield and N use efficiency when compared with systems currently employed.
Investigating Short‐Term Carbon Flows in the Rhizospheres of Different Plant Species, Using Isotopic Trapping
Authors: Cheng Weixin , Coleman David C. , Carroll C. Ronald , Hoffman Carol A. 
Published: July 2010

AbstractMany difficulties exist in studying rhizosphere carbon flows in situ because of limited methodologies. Current photosynthate allocation to root respiration, rhizosphere microbial respiration and soluble root exudates in the rhizospheres of winter wheat (Triticum aestivum L.), tall fescue (Festuca arundinacea Schreb.), and buffalo gourd (Cucurbita foetidissima HBK) were investigated using an isotopic trapping procedure. Plants were grown in containers with 165 g of sandy clay loam soil for 3 wk before the time of 14C pulse labeling. Most root exudates were utilized by the microbes in the immediate rhizosphere and released as 14CO2. Only a small amount of exudates was found in the bulk soil (2.7, 2.5, and 3.7% in the control treatments of wheat, tall fescue, and buffalo gourd respectively). The isotopic trapping mechanism was valid for all three species even though the patterns of total rhizosphere respiration (measured as total 14CO2) rates during the initial 8 h of tracing for the three plant species were different in peak time and peak height. The isotopic trapping procedure can be used in rhizosphere studies for various plant species in principle. Some modifications to the procedure may be needed for different plant‐soil systems.
A Computer Program to Analyze Single‐Season Crop Model Outputs
Authors: Thornton Philip K. , Hoogenboom Gerrit 
Published: July 2010

AbstractComputer simulation models of the growth, development, and yield of annual crops can produce large quantities of data, especially if a simulation experiment involves many treatments and replications across different years. Computer software was written to perform simple analyses of such experiments, allowing the user to identify those treatments that are productive, stable, economically attractive, environmentally sound, or otherwise suitable for the purposes of the investigator. The computer program, which runs on a DOS (IBM‐compatible) personal computer, can interface with output files produced by any crop model run on any other computer that conforms to a common output file structure. Summary statistics for a wide variety of model output variables are calculated and presented to the user in a number of tabular and graphical forms. Net monetary returns and gross margins can also be calculated, and price‐cost variability can be taken into account in the analysis. The user can perform an economic comparison of simulation treatments using mean‐Gini stochastic dominance or, visually, meanvariance analysis. The results of all calculations and analyses are written to an output file that can be manipulated by the user to provide input to a spreadsheet or statistical package for further analysis of the simulated data. The program allows rapid, preliminary analysis of treatments from replicated simulation experiments and can help the user to identify particularly promising treatments that warrant further evaluation.
Calcium Stimulation of Ammonium Absorption and Growth by Beet
Authors: Fenn L. B. , Taylor R. M. , Burks C. M. 
Published: July 2010

AbstractInefficiency in N use by plants contributes to environmental degradation. We examined the use of Ca2+ as a means of increasing NH+4 absorption in beet (Beta vulgaris cv. Detroit dark red). Ammonium absorption was measured in greenhouse and field studies. In the greenhouse, beet plants received full‐strength nutrient solutions with Ca2+: NH+4 molar ratios (MR) of 0, 0.25, 0.5 and 1.0 (Ca2+:NH+4) and a NO‐3 check. Absorption of 15NH+4 was monitored over a 30‐h period. The field production trials occurred over 3 yr on a calcareous Saneli silty clay loam [clayey over sandy or sandy‐skeletal, montmorillonitic (calcareous), thermic Vertic Torrifluvent]. The 15NH+4 absorption study showed the greatest plant weight at the molar ratio (MR) of 1.0 in tops (except in seedlings) and at 0.5 in bulbs. In seedlings, a biomass reallocation occurred in the root‐bulbs from the tops. In both the intermediate and mature growth stages the weight of roots, tops and bulbs greatly increased. In the 15NH+4 absorption studies N concentrations were unchanged or decreased as the Ca2+ concentrations increased, but total N increased. Seedling bulb‐root weight increases were apparenlly metabolite transfer from tops. The intermediate and mature beet plants showed increases in total N. In the greenhouse growth test, vegetative matter increased in excess of 300% at the MR of 0.5 over the check (MR:0). Growth of beet in the 0.5 MR treatment exceeded that on the NO‐3 comparison by 14%. In field testing at a MR of 0.25 (CaCl2:urea), yields increases averaged 26% over 3 yr when compared with urea alone.
Mycorrhizal Dependency and Nutrient Uptake by Improved and Unimproved Corn and Soybean Cultivars
Authors: Khalil Samina , Loynachan Thomas E. , Tabatabai M. Ali 
Published: July 2010

AbstractPlants in nutrient‐deficient soils often benefit when colonized by vesicular‐arbuscular mycorrhizal fungi (VAMF). Plants vary, however, in responsiveness or mycorrhizal dependency (MD). The objective of this work was to evaluate MD within corn and soybean cultivars. Three improved and three unimproved corn (Zea mays L.) and three improved and two unimproved soybean [Glycine soja Siebold & Zucc. and Glycine max (L.) Merr.] cultivars were evaluated for growth response, nutrient uptake (N, P, K, Ca, Mg, and Zn), and root phosphatase activity. Greenhouse studies were conducted with VAMF (Gigaspora margarita or Glomus intraradices) and without inoculation in a Iow‐P soil. The VAMF colonization of roots with inoculation ranged from 62 to 87% for soybean and 49 to 68% for corn. Soybean had a higher MD than corn, but considerable variation occurred within soybean cultivars. Relative growth of the two unimproved soybean cultivars was significantly greater with VAMF colonization than without (Soja, >1900%; Mandarin, >400%). Among improved cultivars, relative growth was less enhanced with colonization (BSR 201, Richland, and Swift cultivars averaged ≈ 200% greater growth with VAMF than without VAMF colonization). An unimproved corn cultivar, Reid Yellow Dent, was unresponsive to mycorrhizal colonization, whereas another unimproved cultivar, Argentine Pop, increased growth 400% with colonization. Total uptakes of N, P, K, Ca, Mg, and Zn were significantly greater (P < 0.001) in mycorrhizal plants, but the concentrations (mg g−1) of N, Mg, and Ca were lower in mycorrhizal plants than in nonmycorrhizal plants. These results suggest that considerable variability exists in MD of corn and soybean cultivars when grown in P‐deficient soils, and the variability extends across both improved and unimproved cultivars.
Development and Growth of White Lupin: Implications for Crop Management
Authors: Duthion Claude , Ney Bertrand , Munier‐Jolain Nicolas M. 
Published: July 2010

AbstractGrain yield of spring white lupin (Lupinus albus L.) varies greatly with sowing date and density. These effects seem to be related to variability of the canopy architecture. To explain and predict such effects, plant growth and development were characterized at different sowing dates and densities and were related to the distribution of seed number between the main stem and branches. ‘Lublanc’ white lupin was sown in field environments for 9 yr, in the greenhouse for 2 yr, and in a growth cabinet for 1 yr at different densities and at different dates within seasons. Current management techniques were applied. Measurements included successive numbers of main‐stem leaf primordia, successive numbers of main‐stem leaves, date of flower initiation on the main stem, date of flowering on the main stem (SF), absorbed photosynthetically active radiation (PAR) by linear sensors (1 yr) or by leaf area index measurement (2 yr), and weekly accumulated dry matter (DM). Flowering date varied between 366 and 621 degree‐days (base 3°C) from emergence and was closely related to the final number of main‐stem leaves. Leaf number was linked to cumulative vernalizing degree‐days received by the apex. Thus, SF was dependent on temperatures during early growth. Absorption efficiency of PAR (εa) varied with plant density, but at high plant densities, regardless of the year, a single curve represented εa change over time. This limit curve gives the maximum possible εa at a given date. Until seed filling began, the coefficient of absorbed PAR conversion was 1.90 g DM MJ−1. Our results contribute to improved management of lupin crops by suggesting cultural practices to minimize climatic hazards from drought and high temperatures.
Mechanisms Responsible for Soybean Yield Response to Equidistant Planting Patterns
Authors: Egli Dennis B. 
Published: July 2010

AbstractIncreased soybean [Glycine max (L.) Merrill] yields in narrow rows can occur without an increase in light interception during reproductive growth. Experiments were conducted for 3 yr in the field to investigate mechanisms responsible for this response. Two Maturity Group IV cultivars (Pennyrile, indeterminate growth habit, and Ripley, determinate growth habit) were grown in 0.76‐m rows or an equidistant planting pattern (each plant ≈0.2 m from all neighboring plants) at a population of 27 plants m−2. Seeds were planted on 5 June 1990, 22 May 1991 and 15 May 1992. The experiment included irrigated and nonirrigated treatments; however, rainfall was above normal every year, and there was no effect of irrigation on yield. Light interception at growth stage R2 was higher (14%) in the equidistant pattern for both cultivars but there was no difference at growth stage R5. Yield of Ripley in the equidistant pattern was significantly higher (9‐19%) than the rows every year, while Pennyrile showed a significant increase only in 1990. The increase in yield occurred because of an increase in seeds per square meter; seeds per square meter was significantly linearly related to fertile nodes (nodes with at least one normal pod) per square meter for Ripley (r2 = 0.42), but not Pennyrile. Ripley showed an increase in fertile nodes per square meter in the equidistant pattern but Pennyrile did not. The data suggest that the increase in seeds per square meter occurred as a result of a more efficient utilization of assimilate associated with more nodes per square meter.
Degradation of Three Warm‐Season Grasses in a Prepared Cellulase Solution
Authors: Magai Margaret M. , Sleper David A. , Beuselinck Paul R. 
Published: July 2010

AbstractInformation is needed on the relationship between anatomical structure and the rate and extent of cell wall degradation in warm‐season forage grasses. The objective was to study the pattern, rate, and extent of tissue degradation of three warm‐season grasses in a prepared cellulase solution, using light microscopy. Most recent fully collared leaf blades from field‐grown big bluestem (Andropogon gerardii Vitman), indiangrass [Sorghastrum nutans (L.) Nash] and switchgrass (Panicum virgatum L.) were cut into 5‐cm sections and digested in 10 mL prepared cellulase solution with an acid‐pepsin pretreatment. All material was in a vegetative state. Leaf segments were retrieved after 3, 9, 24, 48, and 72 h incubation and prepared for light microscopy by fixation, dehydration and embedding in Spurr's low‐viscosity resin. Sections 5 μm thick were made using an ultramicrotome, and undigested tissues in cross section were measured with a computer‐based image analysis system. The proportion of undigested tissue in cross section after 72 h incubation ranged from 25.4% in big bluestem to 35.0% in switchgrass. Switchgrass contained a higher percentage of parenchyma bundle sheath tissue than either big bluestem or indiangrass. Digestion of all tissues except mesophyll and phloem was delayed until after 24 h incubation. Differences among species tended to be greater in extent of digestion than in rate. Degradation of the parenchyma bundle sheath was significantly less in switchgrass than in either big bluestem or indiangrass after 72 h incubation. Digestion of the abaxial epidermis was nearly complete in big bluestem after 72 h incubation. The adaxial epidermis was more readily degraded than the abaxial epidermis. These results imply that differences in digestibility among the three warm‐season grasses could be attributed to differences in the degradation of their individual tissue types.
Soybean Yield Reductions Caused by Defoliation during Mid to Late Seed Filling
Authors: Board James E. , Wier Alan T. , Boethel David J. 
Published: July 2010

AbstractLittle is known about soybean [Glycine max (L.) Merr.] yield response to defoliation during the last half of the seed‐filling period (R6.3 to R7) and how it is affected by source/sink ratio. Because defoliating insect pests in the southeastern USA frequently attack soybean during this period, greater knowledge of yield responses to defoliation at this time would aid in making management decisions. Therefore, the objectives of this field study were to (i) determine yield losses to total defoliation near the temporal midpoint (R6.3) and three‐quarter point (R6.6) of the seed‐filling period; (ii) determine if alterations in source/sink ratio affect this response; and (iii) determine yield component mechanisms responsible for the yield reduction. ‘Centennial’ soybean was planted in 1991 and 1992 near St. Gabriel, LA. Treatments were no defoliation (control), 100% defoliation at R6.3, and 100% defoliation at R6.6 arranged as split plots within high, normal, and low source/sink ratios during seed filling (main plots). Defoliation at R6.3 resulted in 40% yield reduction, whereas defoliation at R6.6 caused a 20% yield loss. Lower yield resulted from reduced seed size. Source/sink ratio did not affect this response. Smaller seed size in both defoliation treatments resulted partly from reduced seed‐filling rate (28% less than control). Shorter effective filling period also contributed to smaller seed size, but this effect was influenced by treatments and years. In conclusion, 100% defoliation during R6.3 to R6.6 must be avoided to maintain optimum yield.