bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trained and Untrained Individual's Ability to Identify Morphological Characters of Immature Grasses
Authors: Fermanian T. W. , Barkworth M. , Lui H. 
Published: July 2010

AbstractIdentifying juvenile grasses is especially difficult because their characteristics are greatly affected by growing conditions. One problem, which affects both computer‐based identification systems and written identification keys, is the inability of users to select the correct alternatives for some morphological characters or structures. This study was designed to determine, for each selected character, whether individuals without training in plant identification could identify each character state correctly as often as trained individuals, and to determine if combining poorly distinguished character states would increase the value of a character for identification of the selected species. seeds or young seedlings of 18 grass species commonly found in turfs of the USA were sown in 125 cm3 plastic plots in a standard greenhouse mix. Untrained participants were students enrolled in an introductory horticulture course on the campus of the University of Illinois and molecularly oriented (not working at the whole plant level) members of the Department of Biology at Utah State University. Observations for trained participants were obtained from sessions held at various locations with faculty members in turfgrass science, plant taxonomists, and graduate students with field experience in grass identification. Considered across all characters, the trained participants selected the correct alternative for a character 59% of the time, the untrained participants 53%. There was no significant association between training group and selection ability for ligule size, sheath, blade width, collar, and pubescence when all species were considered jointly. The frequency with which ligule type was correctly identified was reanalyzed after combining the states of truncate or round and acute or acuminate. This modification increased the frequency of correctly identified, ligule‐type states from 47 to 62% and 31 to 49% for the trained and untrained groups, respectively. On the basis of this study, we would recommend that anyone attempting to construct an identification tool examine both the ability of characters to discriminate among the included species and the ability of expected users to select the correct state or condition of each character.
Alfalfa Persistence and Regrowth Potential under Continuous Grazing
Authors: Smith S. R. , Bouton J. H. , Hoveland C. S. 
Published: July 2010

AbstractAlfalfa (Medicago saliva L.) generally does not persist well under continuous grazing. Experiments were conducted under continuous grazing to compare the persistence and regrowth potential of an alfalfa germplasm (Georgia—Grazed Collection, GA‐GC), selected for continuous grazing, with two hay‐type (Apollo and Florida 77) and two grazing‐type (Travois and Spredor II) cultivars. The germplasm and cultivars were subjected to continuous, heavy grazing by beef cattle for 18 weeks in each of 3 yr to a height of 3 to 5 cm. Wire exclosures rotated at 28‐d intervals on all plots were used to estimate the regrowth potential of each entry during the grazing period. Plant and stem counts were taken before and after grazing each year as estimates of stand persistence. Cultivars differed significantly for stand persistence after 3 yr of continuous grazing with 6 to 9 plants m−2 remaining for the hay‐type cultivars and 40 to 48 plants m−2 remaining for grazing‐type cultivars. The GA‐GC maintained plant densities of 64 plants m−2 while producing the highest forage regrowth compared with all cultivars. Total nonstructural carbohydrates (TNC) in roots at the end of 1986 and 1987 grazing seasons ranged from 256 g kg−1 for Florida 77 to 429 g kg−1 for Travois, suggesting that grazing tolerance may be related to the TNC concentration in roots of alfalfa that had been heavily and continuously grazed. This study indicates that selection for plant persistence under continuous grazing from a broad‐based population improved the grazing tolerance of the resulting germplasm (GA‐GC) while maintaining the potential for good forage yields.
Assessment of Carbon Allocation with Stable Carbon Isotope Labeling
Authors: Svejcar Tony J. , Boutton Thomas W. , Trent James D. 
Published: July 2010

AbstractLabeling plants with isotopic forms of C allows many processes important to agriculture and/or natural resource management to be studied. Most C‐labelling experiments have employed radioactive 14C, but in recent years regulatory constraints associated with use of radioactive materials appear to have curtailed studies which may have benefited from 14C labeling. In this paper, we describe a procedure for using the stable isotope 13C for C labelling. By using gas‐isotope‐ratio mass spectrometry, isotopic differences as small as 0.4 µg of 13C could be detected in the 23‐d‐old cheatgrass (Bromus tectorum L.) we used to demonstrate the technique. The procedure is flexible and can be applied to most plant species and a wide range of research objectives. Because 13C is a naturally occurring stable isotope, there are no regulatory problems, environmental hazards, or health risks associated with its use.
Soil Nitrogen Mineralization in the Presence of Surface and Incorporated Crop Residues
Authors: Smith S. J. , Sharpley A. N. 
Published: July 2010

AbstractThe increasing adoption of farming practices which maintain crop residues on the soil surface has created a need for more detailed information regarding associated soil N availability. This study examines the effects of crop residue placement and type on soil N availability for a range of soils. Representative field rates of alfalfa (Medicago saliva L.), corn (Zea mays L.), oat (Avena saliva L.), peanut (Arachis hypogaea L.), sorghum, (Sorghum sudanense (Pipe;:) Stapf.), soybean (Glycine max L.), and wheat (Triticum aestivum L.) crop residues were applied to eight Oklahoma surface soils. The experiment was conducted under aerobic laboratory conditions at 35 °C, and involved 2‐mm soil particles and 0.25‐mm crop residue materials. The N availability was measured on the basis of indigenous and fertilizer‐derived soil N mineralized during short‐ (14 d) and long‐ (84 d) term incubation. Short‐term, an initial depression (more than 80% with corn) in net mineralization occurred with nonlegume residue additions. The depression was enhanced when the residues were incorporated rather than left on the soil surface. The relative depression was greater with the newly formed, fertilizer‐derived soil N than the older, indigenous soil N. On the other hand, N mineralization was enhanced more than 50% with the alfalfa addition. Effects of crop residue type on N mineralization showed ranges up to threefold or more and generally proceeded in the order alfalfa > peanut > soybean > oat ≥ sorghum > wheat > com. Long‐term, N mineralization for all systems was more comparable to that without residue additions.
Tissue Test for Excess Nitrogen during Corn Production
Authors: Binford G. D. , Blackmer A. M. , El‐Hout N. M. 
Published: July 2010

AbstractSeeming conflict between the need to use N fertilizers and the need to protect groundwater quality requires better tools for distinguishing between fertilizer applications that are essential and those that are excessive. Studies were conducted to evaluate NO‐3 concentration in corn (Zea mays L.) stalks at physiological maturity as the basis for a tissue test to characterize degree of N excess during corn production. Samples of the lower portion of corn stalks were collected from plots in N‐rate experiments at 18 site‐years in Iowa. Observed relationships between grain yields and stalk NO‐3 concentrations indicated sharp breaks between NO‐3 concentrations that were not adequate and those that were adequate for obtaining maximum or near‐maximum yields. When yields were near maximum, stalk NO‐3 concentrations increased linearly with amounts of N fertilizer applied. Stalk samples collected at various times after black layering showed that NO‐3 concentrations remained constant for at least 2 wk. These observations suggest that stalk NO‐3 concentration offers great potential as the basis for a tissue test to characterize degree of N excess during corn production.
Stubble Height Effect on Winter Wheat in the Northern Great Plains: I. Soil Temperature, Cold Degree‐Hours, and Plant Population
Authors: Bauer Armand , Black A. L. 
Published: July 2010

AbstractSoil temperatures at the crown‐depth of winter wheat (Triticum aestivum L.) that effect winterkill are generally known. In contrast, estimates of the effect that duration of the low temperature has on winter survival have not been published for winterhardy cultivars. Objectives were to relate temperature at the 4‐cm soil depth to winter survival and develop capability to estimate survival based on accumulated cold degree‐hours. Field trials were conducted during a 4‐yr period on Williams loam (fine‐loamy, mixed Typic Argiborolls) at Mandan, ND. Soil temperature at the 4‐cm depth was measured at 2‐hr intervals under three cultivars (Roughrider, Mironovskaya and Centurk) grown on four stubble heights (0, 5, 20, and 36 cm) and with two preplant water levels (0 and 50 mm supplemental water applied 1–2 wk before planting). Based on postwinter pretillering plant populations, complete winterkill was effected at about −20 °C soil temperature for Roughrider and Mironovskaya; Centurk did not survive at −18 °C. Population reductions began to occur when 4‐cm depth soil temperatures were about 7 °C warmer than the lethal soil temperature. Duration of the lethal temperature effecting complete winterkill appears to be a matter of hours, based on cold degree‐ hours lower than a threshold temperature. This information, coupled with that of soil temperatures estimated from models, has utility in predicting degree of potential winterkill and reduction in plant populations.
Temperature and Solar Radiation Effects on Potential Maize Yield across Locations
Authors: Muchow R. C. , Sinclair T. R. , Bennett J. M. 
Published: July 2010

AbstractThe objective of this analysis was to use a simple, mechanistic crop growth model to examine the effects of variation in solar radiation and temperature on potential maize (Zea mays L.) yield among locations. Crop phenology and leaf growth were calculated from daily mean temperature data obtained at the five locations studied. Daily biomass accumulation was calculated by estimating the amount of radiation intercepted and assuming maximum crop radiation use efficiency of 1.6 g MJ−1. Grain yield accumulation was simulated using a linear increase in harvest index during grain filling. Observed and simulated grain yields were compared for several sowings at each of five localions ranging from latitude 14°S to 40°N lat. Averaged across sowings, respective observed and simulated oven‐dry grain yields (g m−2) were 816 and 830 at Katherine, Australia; 953 and 908 at Gainesville, FL; 1059 and 1106 at Quincy, FL; 1091 and 1119 at Champaign, IL; and 1580 and 1626 at Grand Junction, CO. Temperature primarily affected growth duration with lower temperature increasing the length of time that the crop could intercept radiation. The solar radiation response was related to the amount of incident radiation and to the fraction of radiation intercepted by the crop. In the tropics (Katherine), high temperature decreased the duration of growth and grain yield, despite high levels of radiation. Only at locations with low temperature and consequent long growth duration. and with high radiation were maize yields simulated to be more than 1600 g m−2 (300 bushels per acre at 15.5% moisture).
Use of Spectral Vegetation Indices to Infer Leaf Area, Evapotranspiration and Yield: I. Rationale
Authors: Wiegand C. L. , Richardson A. J. 
Published: July 2010

AbstractObservations of plant canopies in visible and near‐infrared wavelengths and the calculation of spectral vegetation indices from them are now routine, but a unified rationale for interpreting the measurements has been lacking. Herein we present a rationale that links spectral observations to plant processes and express the relationships in equation form. Specifically, the equations relate vegetation indices or cumulative daily vegetation indices to leaf area index, fraction of photosynthetically active radiation that is absorbed, economic yield, leaf mass, aboveground dry phytomass, and evapotranspiration. Data from the literature demonstrate the relationships. The approach, termed spectral components analysis, assumes that crop canopies display the net assimilate achieved in response to growing conditions experienced and that vegetation indices are a measure of the amount of photosynthetically active and transpiring tissue present. It is expected to hold as long as the size of the canopies achieved by the time reproduction begins and the duration/persistence of the canopies limit economic yield, the situation typical of commercial agriculture. The approach provides a basis for using spectral observations to estimate large area yields and to model effects of multiple stresses on crops and forages.
Environment and Genotype Influence on Grain Protein Concentration of Wheat and Rye
Authors: Fowler D. B. , Brydon J. , Darroch B. A. , Entz M. H. , Johnston A. M. 
Published: July 2010

AbstractProtein is a primary quality component of cereal grains. Protein concentration is influenced by both environmental and genotypic factors that are difficult to separate. In the present study, a series of cultivar and agronomic trials were conducted on several Saskatchewan soil types with the objective of characterizing the influence of genotype and environment on wheat (Triticum aestivum L.) and rye (Secale cereale L.) grain protein concentration and N use efficiency (NUE) for grain protein production. Minimum protein concentration of 95.4 g protein kg−1 dry grain was expressed when cultivars were produced under high productivity conditions on soils with low total plant available N. Minimum protein concentration was maintained until N was no longer the factor most limiting grain yield. At this point, the protein concentration‐N response curve of a cultivar entered an increased phase. Any environmental (e.g., water or time of N availability) or genotypic factor that increased yield potential also increased the amount of N required to initiate the increase phase of the grain protein concentration N‐response curve. Asymptotic maximum protein concentration was determined by both environmental and genotypic factor. Maximum protein concentration at high levels of N varied from 130 to 231 and 107 to 177 g protein kg−1 dry grain for winter wheat and rye, respectively. At low levels of total available N, the NUE for grain protein production approached 80%. The NUE for grain protein production dropped off rapidly for subsequent increments of N fertilizer, approaching zero for maximum grain yield and reaching zero when maximum grain protein yield was achieved. The end of the increase phase of the protein concentration‐N response curve occurred at approximately the same available N level as maximum grain yield. These observations indicate that management systems designed for the production of cereals with high grain protein concentrations will have a very low NUE for grain and grain protein production.
Forage Yield and Quality of Oat Cultivars with Increasing Rates of Nitrogen Fertilization
Authors: Collins M. , Brinkman M. A. , Salman A. A. 
Published: July 2010

AbstractForage yield and several quality parameters of oat (Avena saliva L.) have been addressed in the literature, but the effect of N fertilizer rate on forage yield and quality of oat cultivars, and the possibility of cultivar by N interactions, has received little attention. The objective of this study was to evaluate oat cultivar responses to N fertilization when harvested as forage at heading. Nine adapted oat cultivars ranging from early to late in heading date were grown in four field environments from 1982 to 1984 with five N application rates (0, 28, 56, 84, and 112 kg ha−1). Nitrogen application rates up to 84 or 112 kg ha−1 increased forage yield and increased N concentration in two of three environments. Increasing N application rate increased neutral detergent fiber (NDF) 46 g kg−1 in one environment but decreased it slightly otherwise. In three of four environments, forage yield at heading increased (r2 = 0.66−0.94) linearly with later heading date. Nitrogen concentration generally decreased and NDF, acid detergent fiber, and acid detergent lignin concentrations increased with later heading date. The difference in NDF between the earliest and latest cultivars could affect forage utilization by affecting forage intake. In situations where high quality is important, early maturing oat cultivars might be preferable because they produce higher quality forage. Early harvest would also alleviate competition with an underseeded perennial legume earlier in the season. Application of 84 to 112 kg ha−1 of N produces maximum yields and increases N concentration with generally small effects on fiber concentrations and without increasing lodging.
Nitrogen Transfer from White Clover, Red Clover, and Birdsfoot Trefoil to Associated Grass
Authors: Mallarino A. P. , Wedin W. F. , Perdomo C. H. , Goyenola R. S. , West C. P. 
Published: July 2010

AbstractInformation on N transfer from field‐grown forage legumes to associated grass would contribute to elucidation of N budgets and improved N management of pasture mixtures. This research evaluated N transfer by white clover (Trifolium repens L.) (WC), red clover (Trifolium prutense L.) (RC) or birdsfoot trefoil (Lotus corniculatus L.) (BT), grown with tall fescue (Festuca arundinacea Schreb.) (TF) at various legume proportions. Two identical experiments were established on a Typic Argiudoll soil in Uruguay, one in 1983 (Exp. 1) and one in 1984 (Exp. 2), and each was evaluated for approximately 2 yr. The soil of the area was a fine, montmorillonitic, mesic, Typic Argiudoll. Transfer of N to TF was estimated by 15N isotope dilution, using TF grown alone as the reference crop. Mean values for the proportion of grass N derived from legumes (%NT) were 20% for the 60% harvest after seeding, and later increased up to 60%. The increase on %NT over time was greater for WC‐TF and RC‐TF in Exp. 1 and for WC‐TF in Exp. 2. The annual uptake of transferred N (TNY) averaged 18 and 34 kg ha−1 in 1st and 2nd yr, respectively. The WC‐TF mixture usually showed greater annual TNY than RC‐TF on BT‐TF. Transfer by WC in summer often was greater than for RC or BT. Increasing legume proportion generally resulted in linear increases of %NT for the three mixtures, but TNY either did not change or decreased. We conclude that these legumes transferred small amounts of N shortly after seeding, but transfer increased to significant values with time. The concentration of legume‐derived N in TF herbage increased when legume proportion increased, but the amount transferred was not affected or reduced.
Indole Acetic Acid Production by the Fungal Endophyte of Tall Fescue
Authors: De Battista J. P. , Bacon C. W. , Severson R. , Plattner R. D. , Bouton J. H. 
Published: July 2010

AbstractIncreased plant growth and morphological alterations are characteristics of tall fescue (Festuca arundinacea Schreb.) infected with a fungal endophyte (Acremonium coenophialum Morgan‐Jones & Gams). A study was conducted to determine if there were ancillary plant growth regulators produced by the endophyte, which could account for these vegetative characteristics. Two endophytes, RRC 401 and RRC 347, were isolated from a rhizomatous and upright growing genotype of tall fescue, respectively. These isolates were cultured on laboratory medium, and extracts of this medium were examined for plant growth regulators using thin‐layer and gas chromatography. Only 3‐indole acetic acid (IAA) was detected in culture extracts of this fungus. The in vitro production of IAA by both isolates was confirmed by gas chromatography‐mass spectrometry. This was the first report of IAA production by this endophyte. Indole acetic acid production varied according to the strain, culture conditions, and age. Indole acetic acid in plant material was quantified with an immunoassay. Attempts to relate free IAA concentrations to altered growth expressions characteristic of endophyte‐infected and noninfected rhizomatous and upright growing genotypes of this grass were inconclusive.
Rice, Mungbean, Soybean, Peanut, Ricebean, and Blackgram Yields under Different Intercropping Systems
Authors: Mandal Bijan K. , Dhara Madhab C. , Mandal Barid B. , Das Swapan K. , Nandy Rita 
Published: July 2010

AbstractIntercropping provides farmers profit‐oriented and subsistence‐oriented requirements from the same piece of land. The objective of a 2‐yr experiment on intercropping rice (Oryza sativa L.) and legumes was to assess effect on yield in India. Rice was intercropped with mungbean (Vigna radiata L.), soybean [Glycine max (L.) Merr.], peanut (Arachis hypogaea L.), ricebean (Vigna umbellata L.) and blackgram [Vigna mungo (L.) Hepper.] on a well‐drained sandy loam soil in the Gangetic Alluvial Plains (Fleuvudent). Rice/legume planting ratios (row basis) were 2:1, 4:1 simultaneously planted or legumes were planted (2:1 planting ratio) at 30 d after planting of rice (deferred planting). Control plots were monocrops of rice and legumes with each species fertilized according to soil test recommendations. Rice + mungbean, rice + soybean, rice + peanut and rice + blackgram intercroppings resulted in higher yields than that of rice + ricebean intercropping. Rice + ricebean and rice + blackyielded higher when deferred planting was practised. All intercropping treatments of rice + legumes save rice + ricebean (simultaneous planting) were greater in land equivalent ratio (LER), relative net return (RNR), monetary advantage (MA), etc. The competitive ratios (CR) of rice was above one in deferred planting except rice + blackgram and rice + mungbean in 1985 and only rice + blackgram in 1986. Thus, LER, RNR, and MA showed that intercropping of rice + legumes other than ricebean resulted in greater productivity per unit of land than monocultures.
Yield and Botanical Composition of Alfalfa‐Bermudagrass Mixtures
Authors: Brown R. H. , Byrd G. T. 
Published: July 2010

AbstractThe regions of adaptation of alfalfa (Medicago sativa L.) and bermudagrass [Cynodon dactylon (L.) Pers.) overlap in the southeastern USA, but the compatibility of these species in a mixture has not been described. Two field experiments were conducted to compare the yield and botanical composition of alfalfa‐bermudagrass mixtures with each species grown alone. In the first experiment ‘Apollo’ alfalfa was grown alone and in mixtures with ‘Tifton 44’ bermudagrass fertilized with 0 and 100 kg N ha−1, and compared with bermudagrass fertilized with N at rates of 100, 300, and 500 kg ha−1. In a second experiment Apollo alfalfa was grown alone in 15‐cm rows and in 15‐ and 30‐cm rows in mixtures with ‘Coastal’ bermudagrass. Bermudagrass was also grown alone and fertilized with 100, 200, and 300 kg of N ha−1. Yields of the alfalfa‐bermudagrass mixtures averaged 9.7 Mg ha−1 over both experiments and were similar to alfalfa alone (9.2 Mg ha−1). The mixtures also were similar in yield to bermudagrass fertilized with 200 kg N ha−1 in the second experiment (11.2 Mg ha−1) and between yields of bermudagrass receiving 100 and 300 kg N ha−1 in the first experiment. Alfalfa dominated the mixture in both experiments comprising 100% of the forage in the spring harvests, except for the establishment year in the first experiment. The lowest percentage of alfalfa was in August when in 1 yr it reached 53%. Neither N fertilization nor row spacing of the alfalfa affected yield or botanical composition of the mixture.