bluuebunny/crossref_metadata_2025_split huggingface dataset:
Forage Legume Roots and Nodules and Their Role in Nitrogen Transfer
Authors: Dubach Markus , Russelle Michael P. 
Published: July 2010

AbstractLegumes can transfer significant amounts of symbiotically fixed N to neighboring plants, and a putative pathway for N transfer is decomposition of fine roots (those that are not secondarily thickened) and nodules. Our objective was to quantify the amount of N in living and dead roots and nodules of alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.). These values were used with estimates of root length and nodule numbers that decomposed during a season to estimate the size of this pathway of N transfer. Birdsfoot trefoil and effectively and ineffectively nodulated alfalfa were grown in root observation boxes filled with 15N‐labeled topsoil (Typic Hapludolls). Roots and nodules were removed according to age and analyzed for total N and C. Specific N content of fine roots older than 2 wk was 0.22 mg N m−1 in alfalfa and 0.14 mg N m−1 in trefoil, and did not change with age. Specific N content did not decline in dead, nondecomposed roots of N2‐fixing plants, indicating either that no significant N remobilization occurred or that N import equaled N export in these organs. Large, active birdsfoot trefoil nodules (>2 mm) had twice the N content of large active alfalfa nodules. Dead nodules, observed in birdsfoot trefoil only, had significantly lower N content than live nodules, indicating N remobilization during senescence. Fine roots contained up to 69% of N from fixation in alfalfa and 47% in birdsfoot trefoil, and nodules contained 89% and 94% fixed N, respectively. We conclude that alfalfa releases more N through decomposing roots than nodules, whereas birdsfoot trefoil contributes more N to the soil through decomposing nodules than roots, but neither process could account fully for published estimates of N transfer.
The ALFALFA CATALOG Software Package
Authors: Townsend M. S. , Henning J. A. , Currier C. G. 
Published: July 2010

AbstractDue to modern plant breeding methods, agricultural producers have many cultivars available for many different species. Consequently, it is often difficult to recommend a cultivar for a particular growing area. A list of alfalfa cultivars, germplasms, and breeding lines available was published. However, due to the large number of entries in these publications finding pertinent information about a cultivar, breeding line, or germplasm was tedious. The objectives of this project were to (i) develop a computer program to access the alfalfa information in the original database, and (ii) update the database to include those alfalfa cultivars, breeding lines, and germplasms released through late 1992. A computer program was written using Microsoft QuickBasic, ver. 4.5. The original alfalfa database was converted to ASCII format. The resulting software package is entitled the ALFALFA CATALOG ver. 1.0. Three program files and four data files comprise the ALFALFA CATALOG software package. Users may rapidly search the database and retrieve entries by cultivar name, experimental designation, or germ‐plasm. We also wrote a routine to print a list of all cultivars or germplasms that have a specific combination of traits. These search capabilities will allow plant breeders, extension agents, and consultants rapid access to pertinent alfalfa data. Currently, the ALFALFA CATALOG has 752 entries for cultivars and breeding lines, and 144 entries for germplasms. The database will be updated yearly. In its present form, the ALFALFA CATALOG is probably the most complete compilation of alfalfa cultivars, breeding lines, and germplasms available.
Reflood Timing for Ratoon Rice Grown on Everglades Histosols
Authors: Coale F. J. , Jones D. B. 
Published: July 2010

AbstractRice (Oryza sativa L.) ratooning is commonly practiced in the Everglades Agricultural Area of southern Florida, yet optimum length of the drained period between main and ratoon crops has not been determined. Research was conducted to determine the effect of length of drain period at main‐crop harvest on ratoon rice productivity on an Everglades Histosol. Our research was conducted in 250‐L (0.95 m height, 0.58 m i.d.) custom‐made water control lysimeters filled with a Pahokee muck soil (euic, hyperthermic Lithic Medisaprist). Ratoon reflood timing treatments were 0, 5, 15, 25, 35, and 45 d drained beginning at maincrop maturity. Ratoon‐crop grain yield exhibited a significant quadratic response to length of drain period with maximum grain yield produced at 28 d drained. Ratoon panicle number was not affected by reflood timing, but quadratic responses to length of drain period were observed for grain number and 1000‐grain weight. We propose that the resultant effect of reftood timing on ratoon grain yield was the combined responses to increasing mineral N supply and increasing water stress associated with delayed reftooding. For drained durations =28 d, the beneficial effects of increased mineral N supply resulting from organic matter oxidation resulted in a net increase in ratoon‐crop yield. Conversely, for drained periods >28 d, the detrimental impact of prolonged water stress dominated the response to reflood timing and ratoon rice yields declined.
Fenarimol Tolerance of Roughstalk Bluegrass Overseeded in Bermudagrass Greens
Authors: Johnson B. Jack 
Published: July 2010

AbstractBermudagrass (Cynodon spp.) putting greens are overseeded with cool‐season grasses in the fall to maintain a high‐quality putting turf throughout the southern USA. Perennial ryegrass (Lolium perenne L.) has been the predominant grass used for overseeding until recently, when roughstalk (Poa trivialis L.) has been increasingly used for overseeding. Annual bluegrass (Poa annua L.) is a problem winter annual weed that infests most overseeded bermudagrass greens and the weed must be controlled with a herbicide to maintain a high‐quality putting surface. Fenarimol [ɑ(2‐chlorophenyl)‐ɑ‐(4‐chlorophenyl)‐5‐pyrimidinemethanol] has preemergence herbicidal activity on annual bluegrass, but it may also reduce the germination and establishment of roughstalk bluegrass seedlings. A field experiment was conducted over a 2‐yr period to determine the time interval of fenarimol treatments necessary to avoid injury to roughstalk bluegrass overseeded on a bermudagrass green. Overseeded roughstalk bluegrass tolerated fenarimol when applied as (i) a single application at 2.7 kg ha−1, (ii) two applications of 2.0 kg ha−1 each, and (iii) three applications of 1.4 kg ha−1 each, provided the final application was made ≥ 2 wk before overseeding. Quality and density of roughstalk bluegrass were not influenced by fenarimol, provided the last application was made ≥ 2 wk before overseeding in 1991 and ≥ 1 wk before overseeding in 1992. When the final fenarimol application was made during this period, the transition of overseeded roughstalk bluegrass back to bermudagrass was not affected the following spring and early summer.
Climate Change and Large‐Area Corn Yield in the Southeastern United States
Authors: Stooksbury D. E. , Michaels P. J. 
Published: July 2010

AbstractThere is concern about the negative effects that a possible trace‐gas‐induced climate change will have on crop yields. This study determines the effect of climate change already observed on large‐area corn yield (Zea mays L.) in the southeastern USA. Our multiple regression models differ from most previous large‐area models in two important respects. First, we modeled simultaneously the technological trend and the climate. This is required because of the warming of Southeastern nights during the past 50 yr. Second, we used maximum and minimum temperatures, rather than average temperature. Our results generally associate yield reductions with increases in daytime temperatures during the month of corn pollination. In the Middle and Upper South, increased yield is associated with warming of nighttime temperatures during mid‐season. A trace‐gas‐induced warming should produce minimal change in maximum temperatures. Because projections of future climate generally indicate more night warming than day warming, our results argue that Southeastern corn yield will either change very little or may increase slightly beyond the increase normally expected from technological advancement.
Soybean Leaf Gas‐Exchange Responses to Carbon Dioxide and Water Stress
Authors: Allen L. H. , Valle R. R. , Mishoe J. W. , Jones J. W. 
Published: July 2010

AbstractAs global carbon dioxide concentrations rise, we need to understand the combination of direct effects of this gas and the anticipated effects of climate change, including drought, on physiology and growth of all crops. Effects of CO2 on plants begin at the leaf level; our objectives, therefore, were to determine interrelationships among factors governing gas exchange responses of soybean [Glycine max (L.) Merr.] leaves to elevated CO2 and water stress. Photosynthetic CO2 assimilation and transpiration rates were measured in cuvettes on leaflets of soybean (cv. Bragg) grown in controlled‐environment chambers at 330 and 660 μmol CO2 mol−1 air. Leaflets at high CO2, either water‐stressed or wellwatered, had higher photosynthetic and lower transpiration rates, and therefore higher water‐use efficiencies (WUE), than those at control CO2 levels. As irrigation was withheld during an ll‐d period, WUE decreased about 30 to 50% with respect to the well‐watered treatments. Midday leaf temperature and leaf‐to‐air vapor pressure gradient levels increased as the water stress progressed. For water stress treatments, midday leaf conductance (Gtw) was generally higher and residual internal conductance (Gr) was generally lower in low than in high CO2. Ratios of midday Gr/Gtc were nearly constant throughout the period in both the stressed and the well‐watered treatments. The ratios of intercellular Ci, to ambient Ca, CO2 concentration (i.e., Ci/Ca) during the water stress period remained similar to the respective nonstressed treatments within each CO2 level. These findings support the concept that leaf conductances are governed by CO2 assimilation rates under water‐stressed as well as unstressed conditions.
Herbage and Seed Production of Annual Lespedezas as Affected by Harvest Management
Authors: Davis David K. , McGraw Robert L. , Beuselinck Paul R. 
Published: July 2010

AbstractStriate [Kummerowia striata (Thunb.) Schindler] and korean [K. stipulacea (Maxim.) Makino] annual lespedezas are warm‐season forage legumes grown throughout the southeastern USA for pasture, hay, or seed. They provide high quality herbage during midsummer, when grasses often have poor quality. Limited information is available on harvest management for herbage and seed yield of annual lespedezas. The objective of this study was to determine the effect of cutting height and frequency on herbage production and seed yield of striate and korean annual lespedeza. Two field experiments were performed. The first determined the effects of a one‐ or two‐harvest management system and cutting initially at either 6 or 12 cm above the soil surface on herbage and seed yields. The second experiment was a growth analysis of lespedeza on plots not cut or cut at either 6 or 12 cm above the soil. Maximum herbage accumulation occurred for both species during late August, at ≈ 30% bloom. Harvesting in late August in the one‐harvest management system, yielded more total herbage than harvesting in July and October in the two‐harvest management system. Maximum seed yields were obtained when Marion and Summit were harvested only once in October (1115 kg ha−1 and 751 kg ha−1 of seed, respectively). Cutting height affected Summit more than Marion. Cutting Summit at a stubble height of 6 cm in July reduced both regrowth herbage and seed yields more than cutting at 12 cm. Marion regrowth herbage and seed yields were unaffected by initial cutting height. Growth habit differences between Marion and Summit were probably responsible for differences in response to cutting height. Marion is more prostrate than Summit and thus had more herbage below the cutting height after harvest to provide energy for regrowth.
Soil Compaction and Root Growth: A Review
Authors: Unger Paul W. , Kaspar Thomas C. 
Published: July 2010

AbstractAdverse effects of soil compaction on crop production have been recognized for many years. The objectives of this report were to briefly review the early literature, review the contributions of Dr. Howard M. Taylor (1924–1991) and co‐workers, examine the current status of soil compaction and root growth research, and identify research needs related to soil compaction and root growth. Early in his career, Dr. Taylor and co‐workers established relationships among soil strength, soil water content, and seedling emergence and root growth. These studies showed that root growth and distribution were altered to the point that water and nutrient uptake, and, hence, plant growth and yield, were reduced when soil strength reached critical levels due to natural or induced compaction. That research formed the basis for our current knowledge concerning the effects of compaction on root growth and the alleviation of compaction through soil and tillage management. Usually, not all parts of a root system are equally exposed to compaction under field conditions. Hence, because of compensatory growth by unimpeded parts of the system, only the distribution and not the total length of roots may be altered. Even if compaction limits root growth, weather events sometimes enhance or diminish the effect of root limitation on crop growth. To reduce risks in dry years and to use applied nutrients efficiently, managing soils through the use of tillage and related practices and growing of deep‐rooted crops in rotations will help avoid or alleviate compaction, thus improving root distribution and increasing rooting depth.
Calculation of Optimal Nitrogen Fertilizer Rates
Authors: Bullock David S. , Bullock Donald G. 
Published: July 2010

AbstractAgronomists sometimes fail to apply sound economic theory when recommending economically optimal nitrogen fertilizer application rates. Producers' objectives, producers' attitudes toward risk, and the effect of N on second and higher moments of the yield distribution are often left unstated or ignored. If a farmer knew, prior to N application, the future values of all stochastic factors that affect yield response to N during the growing season, optimal N rates could be established for each individual site‐year. However, farmers do not have perfect knowledge, so recommended rates should not change from year to year for a given site. We propose a more economically sound method for deriving economically optimal N fertilizer application rate recommendations. Our method maximizes profit on average over observed years for a given site. Long‐term field experiments from Illinois demonstrate that our proposed method increases profit from a trivial $0.18 ha−1 yr−1 to a substantial $103.41 ha−1 yr−1, depending on site and cropping sequence. We call for increased collaboration among agronomists and agricultural economists in the economic analysis of fertilizer application.
Predicting Daily Mean Soil Temperatures in the EPIC Simulation Model
Authors: Potter Kenneth N. , Williams Jimmy R. 
Published: July 2010

AbstractSoil temperature is an important component of crop simulation models, because it affects crop growth and development, nutrient cycling, and, in some cases, water infiltration. This study was conducted to determine the efficacy of the EPIC (Erosion/Productivity Impact Calculator) mean soil temperature model and to evaluate the Parton mean surface temperature model developed for a shortgrass steppe in an agricultural simulation model. Simulated mean daily 0.05‐m soil temperatures were compared with measured mean daily 0.05‐m soil temperatures from three locations (Bushland, TX; Boone, IA; and Mandan, ND) for a range of residue management practices. The EPIC model simulated mean 0.05‐m soil temperature trends, although the predicted temperature lagged measured temperatures by 3 to 5 d, and the predicted temperature oscillations were dampened compared with the measured temperatures. The Parton model followed the mean daily temperature oscillations, but generally overestimated early spring mean soil temperatures. Simple adjustments to both models greatly enhanced temperature predictions.
Applications of Stability Analysis for Single‐Site, Long‐Term Experiments
Authors: Guertal E. A. , Raun W. R. , Westerman R. L. , Boman R. K. 
Published: July 2010

AbstractStability analysis, which is the linear regression of treatment yield on the environmental mean yield, has been proposed for use in singlesite, long‐term experiments (treatments applied to the same plots year after year), without first determining if treatment yield reveals a significant relationship with year (experiment years plotted sequentially in time). This research was initiated to demonstrate potential problems associated with stability analysis on long‐term, wheat fertility experiments where treatment yield may be correlated with year. Three single‐site, long‐term experiments were evaluated using stability analysis and linear regression of treatment yield on year. Each study was a replicated, longterm, continuous winter wheat (Triticum aestivum L.) fertility experiment, receiving annual rates of N, P, and K fertilizer. Of the single‐site, long‐term trials evaluated, one was not suitable for stability analysis, as grain yield decreased significantly with each ensuing year that the experiment was conducted. In this case, a negative residual yield response was noted with time (year) in plots receiving N and no P. Therefore, the environmental mean in stability analysis no longer reflected the random influence of climate (e.g., low and high rainfall or temperature) which could be used to decipher variable treatment response in seasonably wet or dry years. Without prior evaluation of the relationship between treatment yield and year in single‐site, long‐term experiments, stability analysis can be inappropriate.
Defoliation Effects and Seed Yield Components in Pearl Millet ✕ Elephantgrass Hybrids
Authors: Diz Diego A. , Schank Stanley C. , Wofford David S. 
Published: July 2010

AbstractPrior to widespread use of seeded hybrids of pearl millet ✕ elephantgrass [Pennisetum glaucum (L.) R. Br. ✕ Pennisetum purpureum Schumach.], management to permit mechanical seed harvesting must be developed. Extreme panicle height and high biomass complicate this procedure. Defoliation management is a potential solution. This field study was conducted on a Mulat sand (sandy, siliceous, thermic Arenic Ochraquults) to (i) evaluate the effects of three defoliation treatments on height of panicles, days to flowering, seed yield components, seed yield, seed germination, and plant survival in four hybrid genotypes and (ii) evaluate the associations among seed yield components under these defoliation treatments through the use of path‐coefficient analysis. In the defoliation treatments, plants were cut zero, two, and three times per year at a 30‐cm stubble height, both in 1991 and 1992. Linear effects of defoliation accounted for 18 to 90% (1991) or 18 to 96% (1992) of the total variation in the characteristics studied. Genotype ✕ treatment ✕ year interactions were common. Panicle height and plant biomass were drastically reduced with two and three cuts per year. Defoliation delayed flowering. Two cuts per year (mid‐June and early August) did not decrease seed yield and seed quality significantly, nor did they affect plant survival Three cuts per year (the last in mid‐September) drastically reduced seed production and seed quality. Path‐coefficient analyses gave significant defoliation treatment and year effects in all traits. Seeds per panicle was always highly correlated to seed yield per plant, due to high positive direct effects and relatively low indirect effects through the other components. Defoliation altered the correlational structure among seed yield components and the compensatory mechanisms among them, but adequate seed production was maintained with two cuts per year.
From Cell Growth to Leaf Growth: III. Kinetics of Leaf Expansion
Authors: Arkebauer Timothy J. , Norman John M. , Sullivan Charles Y. 
Published: July 2010

AbstractPlant growth models have, in general, not considered the detailed aspects of cell expansion and cell division. A key benefit gained by considering growth from a cellular perspective is a more thorough understanding of the role of water relations and plant growth. The objective of this research was to simulate leaf expansion in monocots using a model that incorporates cell division and cell expansion. The core of the model is a module that couples cell division and cell expansion. Assumptions are made concerning the arrangement within the leaf of the cells produced by the cell growth module. Inputs to the model include the total water potential external to the cells and the temperature of the cells. The effects of varying these input parameters on the model outputs (leaf length, leaf area, cell number, elongation rate, and meristem dimensions) are studied. The output is fairly sensitive to the water potential inputs and somewhat less sensitive to the temperature input. These sensitivities are discussed in relation to leaf expansion in field‐grown maize (Zea mays L.) plants under well‐watered and water‐limiting conditions. An extension to the model is described wherein a simple mass balance is calculated on the amount of C produced by the mature portion of the leaf and the amount of C used in the expanding portion.
A Review of Livestock Grazing and Wheat Grain Yield: Boom or Bust?
Authors: Redmon Larry A. , Horn Gerald W. , Krenzer Eugene G. , Bernardo David J. 
Published: July 2010

AbstractWinter wheat (Triticum aestivum L.) grown as a dual‐purpose crop is a unique and economically important resource, especially in the southern Great Plains. Since the last major review of grazing effects on grain yield, in 1956, wheat cultivars have been developed that may affect the productivity of the grazing‐grain enterprise. Thus, we decided to review current research on grazing winter wheat and the effects on grain yield in light of earlier information. During a year of favorable precipitation and adequate to excess soil fertility, tall winter wheat cultivars grazed prior to jointing experienced increased grain yield relative to nongrazed wheat, because of reduced lodging. Current research suggests that the grain yield of semidwarf wheat cultivars is more sensitive to forage removal than for tall cultivars. Grazing termination dates necessary to prevent grain yield reduction of semidwarf cultivars also appear to be much earlier than for taller wheat cultivars. The reason for the difference in grazing tolerance is not clear; however, research suggests that semidwarf cultivars require maximum leaf area at anthesis for maximum grain yield. Tall wheat cultivars are not affected in the same manner, and decreased leaf area due to later grazing does not reduce grain yield of taller wheat cultivars to the same extent as for the semidwarf cultivars. Thus, taller wheat cultivars have the potential for extending the grazing period for livestock producers while producing grain yield similar to that of semidwarf wheat cultivars (which generally produce more grain in a nongrazed situation).