bluuebunny/crossref_metadata_2025 huggingface dataset:
Seed Size and Germination of Hulled and Unhulled Bermudagrass Seeds1
Authors: Ahring Robert M. , Todd Glenn W.
Published: July 2010

Germination procedures used for testing bermudagrass [Cyndon dactylon (L.) Pers.] seed were developed primarily from studies with “common”. Seed of strains other than common, produced under different environmental conditions, may have different germination requirements. Nine strains and five hybrids of bermudagrass, were examined for: 1) differences in seed size, 2) germination capacity in eight different environments, and 3) effects of moist prechill on germination. The objective was to evaluate the differences among strains for seed size and germination requirements.

Seed size among strains were essentially the same during both years of study. Five strains [9945, Guymon, 9958, 10981, and 9958(x)] consistently produce larger seeds. Seed‐set under field conditions would not have to be as high as it was in these strains to have good seed yield potential.

Fresh seed germinated best in a temperature regime alternating between 20 and 30 C. Germination of seed 2 months old, both hulled and unhulled, was significantly greater on substrate moistened with KNO3 than with water. Light, alternating temperatures, and a substrate moistened with KNO3 promoted germination in the dormant or fresh seeds of all but one strain.

Moist prechill treatments tended to reduce viability of the hulled seed, but unhulled seed remained firm and germinaated well after prechill. This finding and the fact that warm alternating temperatures promoted maximum germination suggests that early (February through April) field plantings of hulled seed would not be as successful as late (May through July) plantings. Unhulled seed did not deteriorate as rapidly as hulled seed under moist prechill situations and may find use in February through April plantings.
Herbage Yields and Levels of N and IVDDM from Five Alfalfa Strains of Different Ploidy Levels1
Authors: Arbi Nitza , Smith Dale , Bingham E. T. , Soberalske R. M.
Published: July 2010

Cultivated alfalfa (Medicago sativa L.) cultivars are primarily tetraplolds, and data are sparse about the performance of alfalfa strains of different ploidy levels. Related diploid, tetraploid, and hexaploid alfalfa strains and a ‘Vernal’ check were compared in seeded row plots at Madison, Wisconsin. The soil was a fertile Dodge silt loam (Typic Hapludalf). The alfalfas were harvested during 2 years with two, three, or four cuts annually,, and the forage was analyzed for concentrations of nitrogen and in vitro digestible dry matter (IVDDM). Herbage, N, and IVDDM yields averaged over alfalfa strains were similar for two and three cuts annually, and were lowest for four cuts. Percentages of N and IVDDMw ere in the increasing order of two, three, and four cuts annually and similar for all ploidy levels within a cutting schedule. The 4x strains produced higher yields of herbage, N, and IVDDM than the 2x and 6x strains within each cutting schedule. The 2x strain outyielded the 6x strain with two cuts annually, but the reverse was the case with three and four cuts annually. This same response of strains was apparent in the residual herbage yields, within each cutting schedule, which were in the descending order of two, three, and four cuts annually. It was concluded that among the materials tested the tetraploid level had the highest yield potential and that the experimental diploid was best suited to a two‐cutting schedule. The tetraploid that was synthesized to maximize heterozygosity [4x (70‐44)] outyielded the check cultivar ‘Vernal’ at all cutting frequencies. Lack of maximum heterozygosity in the hexaploid was a possible reason for its comparatively poor performance.
Effects of Annual Weed Control on Alfalfa Forage Quality1
Authors: Temme D. G. , Harvey R. G. , Fawcett R. S. , Young A. W.
Published: July 2010

Establishment of alfalfa (Medicago sativa L.) alone rather than with an oat (Avena sativa L.) companion crop usually results in a reduction in dry matter production. Use of herbicides for weed control during alfalfa seedling establishment also reduces yield since weeds are harvested along with the alfalfa and contribute to forage yield. Thus, if there are benefits from seeding alfalfa alone using herbicides for weed control they would only be expressed in terms of animal consumption, nutritional value, digestability, and finally animal growth or milk production. Consequently, a study was conducted to determine the benefits of annual weed control during alfalfa establishment. Alfalfa was sown into field test plots (Plano silt loam, 3.5 to 4% organic matter, Typic Argindoll, fine, silty, mixed mesic) in April 1976 with an oat companion crop and alone with and without herbicide treatments. Herbicide treatments included were S‐ethyl dipropylthiocarbamate (EPTG) + 4‐(2,4‐dichlorophenoxy) butyric acid (2,4‐DB), and Nbutyl‐N‐ethyl‐α,α,α‐trifluoro‐2,6‐dinitro‐p‐toluidine (benefin). Weeds were also allowed to grow in the absence of an alfalfa or oat seeding. The oat companion crop was harvested at the early dough stage and the alfalfa treatments at first flower, all as chopped hay. The stand of weeds was harvested at the same time as the alfalfa.

The oat hay, weeds, and alfalfa established with and without herbicides, were analyzed in laboratory studies for in vitro digestible dry matter (IVDDM), neutraldetergent fiber (NDF), aciddetergent fiber (ADF), crude protein, and nitrate. A sheep feedingdigestion trial was used to determine the palatability, digestible dry matter (DDM), digestible crude protein (DCP), digestible neutraldetergent fiber (DNDF) and digestible aciddetergent fiber (DADF) of the forages, and N balances of the sheep fed the forages. The four forages were ranked as follows in order of increasing quality as measured by animal intake and digestible dry matter: oat, hay, weed forage, untreated alfalfa, herbicide‐treated alfalfa. The lower quality of the untreated alfalfa in comparison with the herbicide treated alfalfa was attributed to the fact that weeds constituted 50% of the dry weight of the untreated alfalfa stituted 50% of the dry weight of the untreated alfalfa forage. Chemical analysis of the weeds indicated that the Pennsylvania smartweed (Polygonum pensylvanicum L.), shepherds‐purse (Capsella bursa‐pastoris (L.) Medic), and yellow foxtail (Setaria lutescens (Weigel) Hubb.) had the greatest influence in lowering the forage quality. These three weeds, which composed 25% of the untreated alfalfa forage, had the lowest % crude protein and IVDDM and the highest % CWC and ADF. The digestion trial also showed the annual weeds, as a whole, to be the lowest in DCP, DNDF, and DADF. These results confirm that seeding alfalfa alone using herbicides for weed control is beneficial, and that feeding forage thus produced will improve livestock performance.
Evaluation of Legume Mixtures for Hay Plantings1
Authors: Cooper Clee S.
Published: July 2010

Numerous studies have been conducted with grasslegume mixtures for hay and pasture production but few studies have been conducted with legume mixtures. Legume mixtures may be of value in forage production because nonbloating legumes planted with bloating legumes may lessen bloat hazard. Legume mixtures may also be advantageous for use in special purpose mixtures, such as those used for haystockpiling management regimes. We evaluated legume mixtures for irrigated hay production over a 4‐year period in comparison with legumes grown alone. Plantings were made into a Bozeman silt loam (Argic‐Pachic Cryoboroll) soil. Legumes evaluated were sainfoin (Onobrychis viciifolia Scop), birdsfoot trefoil (Lotus corniculatus L.), cicer milkvetch (Astragulus cicer L.), alfalfa (Medicago sativa L.), and red clover (Trifolium pratense L.). Legumes were seeded in 30‐cm row spacings on 1.2 ✕ 6.1 m plots. Legumes in mixtures were seeded in alternate rows. Herbage was harvested twice each year as hay.

Highest yield for the 4‐year period was 36.61 tons/ha for the sainfoin‐birdsfoot trefoil mixture and lowest yield was 26.34 tons/ha for cicer milkvetch grown alone. Yields of other Iegumes grown alone or in mixtures were intermediate. Mixing other legumes with cicer milkvetch increased yields above those obtained with this species grown alone. The contribution of each legume to a mixture was dependent upon the competitiveness of the legume associate. A sainfoin‐alfalfa mixture yield was similar to that for each species grown alone. The merits of growing legume mixtures is discussed.
Gaseous Nitrogen Loss from Soybean Foliage1
Authors: Stutte C. A. , Weiland R. T. , Blem A. R.
Published: July 2010

The loss of non‐elemental N from plant foliage was verified, and the significance of this loss was investigated. Soybean (Glycine max (L.) Merr.) leaf vapors were condensed (–50 C) using a calibrated test tube tra in a closed system. Subsequent N analysis of this condensate revealed water soluble N forms. Since the pyrochemiluminescent technique that was used for N analysis does not detect elemental N, the N present must be in chemically bound forms; preliminary research indicates the N in both oxidized and reduced forms.

Significant losses of N from the determinate cultivar ‘Davis’ were positively correlated to temperature and to transpiration rate under field conditions. These losses, which like transpiration followed a diurnal trend, were greater in early vegetative growth stages than during flowering and pod‐fill. The amount of N lost is significant under the high temperatures of field Conditions and may account for much of the reduction in potential seed yields under this stress condition.
Osmotic Stability of Mannitol and Polyethylene Glycol 20,000 Solutions Used as Seed Germination Media1
Authors: Thill D. C. , Schirman R. D. , Appleby A. P.
Published: July 2010

Solutions of mannitol and high molecular weight polyethylene glycols (PEG) of different osmotic potentials are often used to simulate water stress in seed germination studies. However, little has been reported about the osmotic stability of these solutions. The objectives of this study were to determine the osmotic stability of mannitol and PEG 20,000 solutions, to examine the biological significance of any observed instabilities, and to compare osmotic vs. matric water potential effects on germination of winter wheat (Triticum aestivum L., ‘Nugaines’). Four solutions of mannitol, PEG, and KC1 (standard) with water potentials ranging from −3.5 to −18.0 bars were incubated at 10, 20, and 30 C and water potentials were measured periodically with thermocouple psychrometry. In addition, comparisons were made of the percent and rate of germination of wheat seeds placed in 28‐day‐old and freshly prepared solutions of mannitol and PEG and the percent and rate of seedling emergence from a watered soil media. The osmotic potential of different mannitol solutions and of the −9.1‐ and −17.4‐bar PEG solutions did not change with time. However, the osmotic potential of the −4.0‐ and −6.4‐bar PEG solutions decreased 1.0 bar. Percent and rate of germination of wheat was the same in the 28‐day‐old and in freshly prepared mannitol and PEG solutions; but at equal potentials, the germination rate was most rapid in the mannitol solutions. Wheat emergence rate from watered soil was linearly related to the germination rate in PEG, but not in mannitol solutions.

Hence the slight instability of PEG solutions appears to be of no biological consequence in seed germination studies, and wheat seed emergence rates at different soil matric potentials can be approximated from germination rates in PEG osmotic solutions.
Carbohydrate Sampling in Kentucky Bluegrass Turf1
Authors: Sheffer K. M. , Watschke T. L. , Duich J. M.
Published: July 2010

The percent total nonstructural carbohydrate (TNC) is often used as an indicator of the physiological status of cool season turfgrasses. However, the time of sampling during the day and the plant parts used for analyses may influence results. Growth habit differences of cultivars may also influence the TNC level of plant parts and the rate of accumulation at different times during the day. The purpose of this research conducted on Kentucky bluegrass (Poa pratensis L.) was to determine 1) TNC of five cultivars over three mowing managements, 2) whether TNC of leaf parts (blade or sheath) or the entire leaf (blade plus sheath) provided the best statistical separation of treatments, and 3) diurnal fluctuation of leaf blade TNC in cultivars of diverse leaf blade orientation.

Five Kentucky bluegrass cultivars (‘Merion’, ‘Pennstar’, ‘Baron’, ‘Bonnieblue’, and ‘K‐150A’) maintained at three cuttings heights (1.3, 2.5, and 5.1 cm) in the field were utilized in these experiments. These cultivars were art of the 1972 Northeastern Regional Test established in 1972 on a Hagerstown soil (fine, mixed, mesic Typic Hapludalf). Upper canopy leaf blades (reel mower clippings), leaf sheaths, and entire leaves (blade and sheath) were analyzed for TNC. Blade tissues from intact tillers of Merion were analyzed for TNC and compared with upper canopy leaf blade TNC. Upper canopy leaf blades of Merion and two cultivars (‘Brunswick’ and ‘K‐183’) having diverse leaf blade orientation were sampled diurnally on 2‐hour intervals for TNC

Cuttings heights significantly affected TNC regardless of the tissue fraction analyzed. The 2.5‐cm height had significantly higher TNC than the 1.3 and 5.1 an heights. Entire leaf TNC provided a greater statistical cultivar separation than did sheath or blade tissue alone. K‐150A had significantly higher entire leaf TNC than Pennstar, Baron, and Bonnieblue, while Merion was also higher than Pennstar and Baron. Upper canopy leaf blade tissue of Merion had a much higher TNC level than leaf blade samples which included lower blades. The TNC of blade tissue was found to fluctuate significantly within 2 hours. Cultivars with different blade orientation exhibited similar diurnal TNC patterns. On the basis of these results, future TNC analyses should utilize the entire leaf (blade and sheath) for optimum statistical separations.
Temperature Effects on Growth and Manganese Tolerance in Tobacco1
Authors: Rufty Thomas W. , Miner G. S. , Raper C. D.
Published: July 2010

Symptoms of Mn toxicity in tobacco (Nicotiana tabacum L.) are often observed in the mountain region of North Carolina at soil acidity and soil test levels of Mn which do not produce toxicity in the piedmont. Although genotypic differences between tobacco types grown in the regions may contribute to the differential response, variations in temperature between the regions may also be involved. To investigate the effects of temperature on plant growth and Mn tolerance, tobacco plants of a prevalent cultivar (‘Coker 347’) for the piedmont region were grown in sand culture at day/night temperatures of 22/18, 26/22, and 30/26 C. Manganese was applied daily at rates of 10, 20, 40, 80, and 120 mg/liter in a complete nutrient solution. Plants were sampled weekly during a 6‐week growth period and evaluated for visual toxicity symptoms, dry weight. Mn concentration, relative growth rate (RGR), and relative accumulation rate (RAR) of Mn.

Plant tolerance to high rates of applied Mn increased with increasing temperature despite significantly greater tissue concentrations of Mn during early growth. Tissue levels of Mn in leaves associated with the appearance of visual toxicity symptoms were 700 to 1,200 mg/kg dry wt at 22/18 C, 2,000 to 3,500 mg/kg at 26/22 C, and 5,000 to 8,000 mg/kg at 30/26 C. Mn toxicity symptoms were more severe in immature leaves and often decreased as the leaves matured even though the concentration of Mn in the leaves increased. The RGR of leaves during the exponential growth phase increased with increasing temperatures at each Mn rate, but the RAR of Mn was unaffected by either temperature or applied Mn rate. It is proposed that the increased tolerance to high levels of tissue Mn by plants grown in warm temperatures is associated with more rapid rates of leaf expansion accompanied by increased vaculor capacity for disposal of accumulated Mn.
Assimilate Redistribution from Soybean Pod Walls During Seed Development1
Authors: Thorne John H.
Published: July 2010

Accumulation of dry weight by soybean seeds occurs at a linear rate in spite of daily fluctuations in photosynthate production. This suggests a possible role for assimilate redistribution from storage in maternal fruit tissues to developing seeds. Because of their proximity to the seed, pod walls were suspected as temporary storage organs for photosynthate and nitrogenous assimilates.

Populations of Norman (OO maturity) and Amsoy 71 (II maturity) soybeans [Glycine max (L.) Merr.] were field‐grown in 1977 on Cheshire fine sandy loam (Typic Dystrochrept). Weekly during reproductive growth, developing fruit were harvested and assimilates in pod walls extracted and colorimetrically determined. At midpodfilling, pods from three canopy strata were also harvested diurnally and analyzed. From the examination of dry weight and assimilate levels within these samples, evidence of storage and redistribution from pod walls was obtained.

Prior to mid‐podfilling stage both cultivars accumulated maximum pod wall dry weight; Norman 290 mg pod wall‐1 on 11 August and Amsoy 71 170 mg pod wall‐1 on 25 August. Pod walls of Norman redistributed 112 mg of previously accumulated dry matter, occurring when incipient canopy senescence probably would have otherwise precluded continued linear seed growth. Assuming that these pod wall assimilates were transported to the enclosed seeds and an efficiency of conversion to seed of 41%, the redistributed materials accounted for 12.7% of the final seed yield per plant in Norman while only 1.8% in Amsoy 71.

Pod walls were found to store and later redistribute starch, reducing sugars, and nitrogenous materials. The sucrose present was almost entirely in the major pod vascular bundles. Starch was a major storage product, but there was no significant diurnal variation in the amount. However, significantly more starch was accumulated by Norman pod walls in the upper third of the canopy. Glucose and fructose accumulations were depleted by redistribution in approximately the same time period as starch and nitrogenous materials.

The data suggest that, in extremely short season cultivars such as Norman, assimilate storage and later redistribution by pod walls to the developing seeds may serve to effectively lengthen the period of podfilling and thus contribute significantly to final seed yield.
Salinity‐Induced Modifications in the Response of Maize to Water Deficits1
Authors: Stark J. C. , Jarrell W. M.
Published: July 2010

In many crop species, salinity induces physiological and morphological adjustments which assist in the maintenance of a favorable water balance. Adjustments such as these may also be effective in modifying the response of salinized plants to drought. This study was designed to evaluate the effect of salinity pretreatment on the response of maize to matric water stress.

Maize (Zea mays L.) was grown in sand culture tanks at four levels of nutrient solution salinity, produced with an equivalent mixture of CaCl2 and NaCl: −0.4, −2.4, −4.4, and −6.4 bar osmotic potentials. When the plants were 35 days old, irrigation was stopped and a period of drought stress began. When predawn leaf xylem water potentials (Lψt in all but the highest salinity treatment had dropped below −15 bar, irrigation was resumed. Prior to, during, and after the drought period, rates of leaf blade elongation, Lψt, and relative water content (RWC) were measured.

The lowest rates of leaf blade elongation prior to drought occurred in the high salinity treatments. However, 5 days after discontinuing irrigation, leaf blade elongation in the −0.4 bar treatment had nearly ceased, while the rate for the −6.4 bar treatment slowed considerably but continued to be measurable for 9 days. Plants from the high salinity treatment also did not show the rapid decreases in Lψt exhibited in the other treatments. This response was presumed to be due primarily to salinity‐induced reductions in the transpiration rate which prolonged the period of adequate water supply. Elongation rates partially recovered after the plants were rewatered, but the plants from the high salinity treatment again resisted rapid change.

Salinity pretreatment altered the relationship between elongation and Lψt indicating that loss of turgor during drought may be partially moderated by preconditioning with osmotic stress. The water desorption characteristics of maize were significantly modified by any increase in salinity above that of the control solution.
Inheritancee of Tolerance or Resistance to Manganese Toxicity in Soybeans
Authors: Brown J. C. , Devine T. E.
Published: July 2010

Soybeans (Glycine max L. Merr.) differ in their tolerance to Mn. The objective of this study was to determine the nature or mode of inheritance of Mn tolerance in soybeans. Test plants were Forrest (Mn‐intolerant, Fe‐inefficient), T203 (Mn‐tolerant, Fe‐inefficient) and their F2 progeny Forrest × T203 (F×T) and T203 × Forrest (T×F); and Bragg (Mn‐intolerant, Fe‐efficient), Lee (Mn‐tolerant, mod. Fe efficient) and their F2 progeny, Bragg × Lee (B×L), and Lee × Bragg (L×B). The plants were grown in Mn‐toxic soil and in nutrient solutions containing 0.35 and 0.65 mg Mn/liter. Only T203 did not develop some Mn‐toxicity symptoms under conditions of relatively high Mn. The order of symptom severity was Forrest ≥ Bragg > Lee > T203. Manganese toxicity symptoms also varied among the F2 progeny of reciprocal crosses. The leaves of both parents and progenies contained about 500 mg Mn/g dry matter. Some factor(s) other than Mn concentration in the plants appeared to cause the Mn‐toxicity symptoms. The Fe concentration in plant tops was related somewhat to Mn‐toxicity symptoms in that the Fe concentrations were usually greater in Mn‐intolerant than in Mn‐tolerant genotypes. Control of tolerance to excess Mn appeared to be multgenic rather than controlled by a single gene locus. Reciprocal differences in progeny suggested that cytoplasmic inheritance influenced Mn tolerance. Crop failure can be avoided by selecting a Mn‐tolerant soybean to be grown in a soil relatively high in available Mn.
Adaptation of Cotton Genotypes to an Acid, Manganese Toxic Soil1
Authors: Foy C. D. , Webb H. W. , Jones J. E.
Published: July 2010

Certain soils of the Eastern Cotton Belt are potentially Mn‐toxic. The problem is not always economically prevented or corrected by conventional soil management practices. An alternative or supplemental procedure is to develop plant genotypes having superior resistance to Mn toxicity.

Sixty‐five cotton (Gossypium species) genotypes (cultivars, strains, and breeding lines) were screened in greenhouse pots of an acid (pH 5.1), Mn‐toxic Grenada (fine silty, mixed, thermic, typic, Fragiudalffs) silt loam. Nine of these genotypes, plus two from Brazil, were compared on the same soil at pH 5.1 versus pH 6.9. The cotton germplasm evaluated differed widely in resistance to Mn toxicity as indicated by “crinkle leaf” symptoms and vegetative top dry weight. Genotypes showing greatest resistance included C310,73‐307, LaDSIS 12513; and LaDASB 12609. Manganese sensitive genotypes included C‐Sgl,70‐517; C‐417‐2912; and Coker 201.

Top dry weights of cotton genotypes on the unlimed, Mn‐toxic Grenada soil at pH 5.1 were negatively and highly significantly correlated with crinkle leaf rating. However, top dry weights were not significantly correlated with Mn concentrations in either the two youngest leaves (fourth or fifth) or in samples composed of the three youngest leaves plus petioles. Hence, different internal Mn concentrations are required to induce crinkle leaf symptoms and reduce top dry weights in the different genotypes studied. Crinkle leaf symptoms were significantly and positively correlated with Mn concentrations in the two youngest leaves but not with those in leaf plus petiole samples.

Results indicate that cotton genotypes differ significantly in tolerance to excess Mn. The development and use of Mn tolerant cultivars would be helpful in situations where the control of Mn toxicity by soil management may not be economically feasible.
Seed Element Uptake, Grain Yield, and Bird Damage of Methiocarb‐Treated Sorghum Hybrids1
Authors: Duncan R. R. , Boswell F. C.
Published: July 2010

Bird damage to ripening grain sorghum [Sorghum bicolor (L.) Moench] is a multi‐million dollar problem in the U.S.A. Methiocarb [4‐(methylthio)‐3,5‐xylyl methylcarbamate] (MesurolR) is a chemical insecticide which provides broad spectrum nonlethal avian repellency. This chemical insecticide is not labelled for spray application on ripening grain. This field study, conducted on a Cecil sandy loam soil (Typic Hapludult) during the 1978 and 1979 growing season, sought to investigate uptake of elements into the seed, yield and yield components, height, and bird damage ratings of five sorghum hybrids and to compare results on methiocarbtreated and check plots.

Spray treatments, applied in a randomized block split plot design, significantly reduced seed concentrations of N, K, Mn, and Cu, increased P, and did not affect Zn and Fe. The reduction in N resulted in a 5.1% reduction in crude protein. Copper concentration in the seed was reduced by more than 25% after methiocarb treatment. Grain yields were 1,080 kg/ha higher on the treated than on the check plots. Test weight was 2.2 kg/hl higher, 300‐kernel weight was 0.7g higher, plants were 8 cm taller, and bird damage was 39% lower on the treated than on the check plots. Correlation Coefficients were considerably different on the treated versus check plots, especially as related to N content, test weight, and bird damage influences on yield. Methiocarb treatment of ripening grain sorghum provided an effective chemical method for nonlethal bird repellency and more stable yields under bird pressure. However, the significant decrease in N would result in a lower crude protein content. The additional element changes due to methiocarb treatment coupled with reduced crude protein may have a major impact on feed rationing and utilization. The beneficial aspects of this chemical treatment should be weighed against the detrimental aspects when using the material during grain filling.
Variability Observed in Centipedegrass Grown from 60Co Irradiated Seed1
Authors: Dickens R. , Johnston W. J. , Haaland R. L.
Published: July 2010

Centipedegrass [Eremochloa ophiuroides (Munro) Hack.] has shown limited variability morphology and poor cold tolerance in the 64 years since its introduction into the United States. Variation in morphology and other parameters has been increased in other species by subjecting seed or vegetative parts to ionizing radiation. The purpose of this study was to observe and measure variation in morphology, cold tolerance, and growth habit of centipedegrass grown from irradiated seed. Centipedegrass selections grown from seed exposed to gamma radiation (0 to 80 kR) from a 80Co source were observed for variability in morphology, cold tolerance, and growth habit. No seedling emergence occurred at exposures greater than 40 kR. Irradiated plants had blade widths of 3.7 to 6.8 mm (controls 4.0 to 6.1 mm), blade length of 1.8 to 6.3 cm (controls 2.5 to 4.7 cm), and internode lengths of 0.6 to 4.1 cm (controls 2.0 to 4.1 un). Approximately 7% of the irradiated plants had a dwarfed growth habit, primarily due to shortened internode length. Environmental chamber tests indicated that several irradiated selections were equal or superior in cold tolerance to nonirradiated controls, and to ‘Oklawn’, ‘Tennessee Hardy’, ‘Mississippi 2’, and FC‐2. In field studies conducted on a Dothan sandy loam (Plinthic Paleudult), more than 40% of the irradiated plants had an establishment rate from sprigs equal to that of the controls; however, none was superior and 4% were inferior. Variability was also noted in turfgrass color and seedhead production among the irradiated selections. Seven percent produced no seedheads during the 2 years following establishment. Variability observed in these studies indicates the potential use of gamma radiation of seed to improve several turfgrass quality parameters in centipedegrass.
Organic Matter and N Effects on Soil Nitrite Accumulation and Resultant Nitrite Toxicity to Tobacco Transplants1
Authors: Hamilton James L. , Lowe Richie H.
Published: July 2010

Extended rainy periods during the first few weeks after setting tobacco (Nicotiana tabacum L.) may result in a disorder of tobacco called organic matter toxicity. The decay of organic matter in a soil with moisture levels near field capacity (where O2 diffusion is slower) may deplete the soil O2 enough that nitrite accumulates. Our purpose was to study the accumulation of nitrite in soil with organic matter and N added, and the toxicity of nitrite to tobacco.

To determine the effects of nitrite, burley tobacco (‘Ky 14’) was transplanted into pots containing gravel and irrigated with half‐strength Hoagland solution plus 0, 5, 10, and 15 ppm of nitrite. Tobacco root tips were killed when ntrite concentrations exceeded 5 ppm.

To determine the effects of organic matter and N fertilizer of nitrite accumulation in soil, we determine weekly for 8 weeks the nitrite concentration in pots with: a) organic matter and N fertilizer added, b) only N added, and c) neither organic matter nor N added (controls). Moisture was adjusted to 90% field capacity each day. Tobacco plants were transplanted into the pots at 2, 4, and 6 weeks after preparing the treatments. Nitrite accumulated in the soil layer containing organic matter for 2 weeks, reaching a concentration of 60 ppm. It then started to decrease but remained at toxic levels for 5 weeks. Where no organic matter was added with the N, nitrite levels were toxic only in the sample taken the first week. Tobacco plants transplanted to soil 2 weeks after organic matter was added never grew or developed a root system. The dry weight of plants transplanted 4 weeks after organic matter was added was about one‐half that of the control and plants transplanted 6 weeks after treatments were applied did not differ.
Legume and Mineral N Effects on Crop Yields in Several Crop Sequences in the Upper Mississippi Valley1
Authors: Baldock Jon O. , Higgs Roger L. , Paulson William H. , Jackobs Joseph A. , Shrader William D.
Published: July 2010

The total effect of legumes on subsequent crop yields may be divided into two categories: (i) the effect of the N that they supply, and (ii) the net effect of all other contributions. Knowing the size of these two effects, plus the N response of the subsequent crops, allows N fertilization to be optimized for decreased energy use and for reduced pollution potential. Because the size of the legume effects vary, a study was made to estimate them on a mesic, Typic Hapludalf soil at Lancaster, Wisconsin from 1967–1976. The crop species included alfalfa (A, Medicago sativa L.), corn (C, Zea mays L.), oats (O, Avena sativa L.), and soybeans [S, Glycine max (L.) Merr.] in five crop sequences: continuous C, CSCOA, CCCOA, CCOAA, and COAAA. Four N treatments: 0, 84, 168, and 336 kg/ha were applied only to C. Crop sequence phases were assigned to whole plots in a randomized, complete block design with the N treatments in subplots. There was a highly significant effect of years on all crops due to weather variation and crop variety changes. Soybeans and A did not respond to residual N. Alfalfa yields were the same in all rotations (7.6 ± 0.04 metric tons dry matter/ha/year). The mean 0 yield (Y, quintals/ha) response to residual N (kg/ha) was described by Y = Minimum C(18.4 + 0.0354N), 24.93. Both A and S increased yields of C following these legume crops. Most of the increase was due to their N contribution, which was estimated with a Mitscherlich‐Spillman N response model as 50, 66, 51, 25, 3, 84, 24, and 71 kg N/ha to CSCOA, CSCOA, CCCOA, CCCOA, CCCOA, CCOAA, CCOAA, and COAAA, respectively. The increases in C yields above that due to the legume N were estimated as the difference between the predicted maximum rotational and continuous C yields, specifically: 11, 8, 9, 4, 4, 11, 6, and 11 quintals/ha (in the same order as above).
Herbage Dry Matter Yields of Switchgrass, Big Bluestem, and Indiangrass with N Fertilization1
Authors: Hall K. E. , George J. R. , Riedl R. R.
Published: July 2010

Herbage dry matter (DM) yield potential and N requirement of native perennial, warm‐season grasses must be known before these species can be effectively used in forage‐livestock systems. This study was initiated to determine the herbage yield response of ‘Blackwell’ switchgrass (Panicum virgatum L.), ‘Kaw’ big bluestem (Andropogon gerardi Vitman), and ‘Nebraska 54’ indiangrass (Sorghastrum nutans L. Nash) to N fertilization.

Four replications of a randomized complete block field experiment were established on a Clarion loam (Typic Hapludoll) soil in 1971. A four‐cut management system was used in 1974; a two‐cut system was used during 1975–1976. Applications of ammonium nitrate (34‐0‐0) were made on 21 May 1974 and 13 May 1975 at 0, 75, and 150 kg N/ha levels. Levels of 0, 75, and 150 kg were applied in 1976 as urea (45‐0‐0) on 22 May and again on 3 July after the first harvest. Two of the four replications received 50 kg P/ha as triple superphosphate (0‐46‐0) and 100 kg K/ha as K2SO4 . MgSO4 (0‐0‐22) on 7 May 1976. The K source included 60 kg Mg/ha and 118 kg S/ha.

Switchgrass, big bluestem, and indiangrass produced herbage dry matter (DM) yields of 6.14, 6.29, and 5.59 metric tons/ha, respectively, when averaged over N levels and years. In 1974, big bluestem out‐yielded the rest, and in 2 out of 3 years indiangrass yielded significantly less than one or both of the other species. All species generally responded positively to N through 75, and often through 150 kg N/ha.

No herbage yield response was observed in 1976 to applied P and K fertilizers, the latter containing both S and Mg.

Herbage DM yields generally increased with each of three successive harvests in 1974, whereas second harvest yields decreased with a two‐cut management system used in 1975 and 1976. Relatively unfavorable July–August precipitation seemed primarily responsible for lower second harvest DM yields.

A 5 Oct. 1974 harvest of aftermath herbage cut at a 5‐cm height suggests that 2.2 to 2.4 metric tons/ha of herbage would be available for use by nonlactating beef cows. No species difference in DM yield was observed, suggesting equal carrying capacity/ha, for the aftermath.
Water Use by Forage Species1
Authors: Fairbourn Merle L.
Published: July 2010

Forage production on the High Plains of Western United States might be done more economically if research provided more water‐use information for species. A study was made to determine (1) water‐use efficiency and (2) ability to use available soil water during a harvest growing period. Forages common to the area were evaluated in both greenhouse and field environments. The legume species evaluated were ‘Alsike’ clover (Trifolium hybridum), ‘Dawson’, ‘Fremont’, ‘Ladak’, ‘Team’, ‘Travois’, and ‘Vernal’ alfalfa (Medicago sativa L.), ‘Lutana’ cicer milkvetch (Astragalus cicer L.), and ‘Remont’ sainfoin (Onobrychis vicaefolia Scop.). Pasture grasses evaluated were ‘Fawn’ tall fescue (Festuca arundinacea Schreb.), Garrison creeping foxtail (Alopecurus arundinaceus Poir), ‘Latar’ orchardgrass (Dactylis glomerata L.), ‘Grennar’ intermediate wheatgrass [Agropyron intermedium (Host) Beauv. L.], thickspike wheatgrass [A. dasystachyum (Hook) Scribn.] and ‘Regar’ bromegrass (Bromus biebersteinii Roem & Schult.); while range grasses were blue grama [Bouteloua gracilis (H.B.K.) Lag], crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.], slender wheatgrass [A. trachycaulum (Link) Malte], western wheatgrass (A. smithii Rydb.), and green needlegrass (Stipa viridula Trin.). The study was made on Altvan soil, a fine, sandy, clay loam belonging to the mixed mesic family of aridic arguistolls. Water use was monitored by gravimetric method and by tensiometers in the first and second studies, respectively. Transpiration in the greenhouse during a crop growing period ranged from 7.2 cm for the milkvetch to 15.5 cm for Regar bromegrass. Blue grama had the highest water‐use efficiency of all species but was able to utilize only a relatively small amount of the available water in forage production. Growing the plants in a field environment increased evapotranspiration by 100 to 200% compared with that in the greenhouse. Thickspike wheatgrass appeared to be capable of adapting to either a semiarid or humid climate but range grasses studied were unable to use large amounts of available water.
The Mitscherlich Plant Growth Model for Determining Critical Nutrient Deficiency Levels1
Authors: Ware G. O. , Ohki K. , Moon L. C.
Published: July 2010

The success of a plant tissue analysis program depends on the calibration relating growth and nutrient concentration in specified plant tissues for each essential element. The minimal nutrient concentrations in tissues associated with maximum growth have been determined from calibration curves that were drawn free‐hand to best fit the respective X and Y values in graphical plotting. Statistical models to establish critical deficiency levels related to 90% maximum growth are desirable to reduce the arbitrariness of the graphical procedure.

A modified Mitscherlich response equation was used to quantify critical deficiency levels by characterizing plant growth as a function of tissue nutrient concentration. The model presented is y = β(1 — γe‐ax) where y is the plant yield at tissue concentration x, and α, β, and γ are parameters to be estimated. Critical deficiency levels determined from the Mitscherlich model were significantly greater (P < 0.05) than the previously reported nutrient values of the same studies utilizing the graphical procedure.
Physiological Responses to Wind and Sandblast Damage by Grain Sorghum Plants1
Authors: Armbrust D. V.
Published: July 2010

Yield depression due to physical damage by wind and windblown soil (sandblast damage) is well known. Less well known is the reason for the yield reductions by sandblast damage. The objective of the research was to determine if this yield depression was due to a simple loss of photosynthetically active leaf tissue or to physiological changes within the plant.

Physiological responses of growth chamber grown RS 626 grain sorghum (Sorghum bicolor L. Moench) to injury by wind (13.4 m/sec), wind plus sand (10, 20, 30, 40, 50, 60, and 70 kg), and partial defoliation (removal of the distal one‐fourth and one‐half of each leaf) were evaluated. Wind and wind plus sand treatments were conducted in a wind tunnel. Net photosynthesis, dark respiration, total chlorophyll, dry weight, and leaf area were determined 1, 3, and 7 days after treatment.

Dry weight production increased at low sand levels (< 30 kg) and decreased with higher sand exposure. Reduced growth of sandblasted grain sorghum is caused by loss of viable leaf tissue and physiological changes, which are mainly reduced photosynthesis and increased respiration. It is not clear from this study if these changes result from partial defoliation, short‐term high‐intensity moisture stress, or a combination of both.
Feed Quality of Hay Containing Perennial Broadleaf Weeds1
Authors: Dutt T. E. , Harvey R. G. , Fawcett R. S.
Published: July 2010

Many studies have been conducted to determine how to control perennial broadleaf weeds in alfalfa (Medicago sativa L.) swards, but little information is available on the effects of these weeds on forage utilization by ruminant animals. Therefore, alfalfa or alfalfa‐grass mixtures infested with yellow rocket (Barbarea vulgaris R. Br.), white cockle (Lychnis alba Mill.), and dandelion (Taraxacum officinale Weber.) were treated with herbicides to provide differences in weed composition of harvested forage. Differences in intake, digestibility, and nutrituve value index between weedy and weed‐free forages were determined by feeding hay from the various herbicide treatments to goats in stall trials. Observations indicated that dandelion and white cockle were palatable and yellow rocket was unpalatable.

Animal intake, in vivo digestibility, and nutritive value index werereduced by an infestation of yellow rocket but not by white cockle in alfalfa‐grass mixtures. Crude protein concentration and in vitro digestibility were highest in dandelion, intermediate in white cockle, and lowest in yellow rocket. Based on the small differences in quality observed between most of the weedy and weed‐free forages, we concluded that only yellow rocket would reduce the feed value of hay for ruminant animals.
Interaction of Atmospheric CO2 Enrichment and Irradiance on Plant Growth1
Authors: Sionit Nasser , Hellmers H. , Strain B. R.
Published: July 2010

Atmospheric carbon dioxide and irradiance are important factors affecting growth and yield of plants. Due to the wide variation in irradiance in natural plant stands and the reportedly increasing carbon dioxide concentration in the global atmosphere, it is essential to study the interacting effects of these factors on the growth and production of crop plants. Growth analysis techniques were used to study the interaction of atmospheric CO2 concentration (350 and 675 µl/l) and photosynthetic photon flux density (PPFD) (600 and 1200 µEM−2 s−1)on four species (including both seed and root crops) grown in controlled environment chambers of the Duke University Phytotron. The plants were soybean (Glycine max L. Merr.), radish (Raphanus sativus L.), sugarbeet (Beta vulgaris L.), and corn (Zea mays L.). Total dry matter production increased in all species of plants and at all growth stages with both increased CO2 concentration and PPFD levels, and the maximum dry matter was produced at the highest combined levels of CO2 and PPFD. The dry weight increase varied between the different species and between plant parts within a species. High levels of CO2 and PPFD caused a greater increase in net assimilation rate in the plants during early growth stages than in later stages because the first two or three young, rapidly growing leaves were very efficient photosynthetic organs. A high CO2 or PPFD level resulted in decreasing leaf area ratios with increasing plant age for all the species due to a rapid increase in stem and root growth later in fruit production, and to a decreasing specific leaf area.

Corn, having the C4 pathway of photosynthesis, showed less response to increased CO2 and PPFD than the three C3 species. Increasing the atmospheric CO2 concentration from 350 to 675 µl/liter at low and high PPFD levels produced dry matter increases of 72.7 and 76.4%, respectively, in soybean, and 18.9 and 18.6%, respectively, in corn at 50 days after planting. None of the species tested were light saturated at levels available in the standard fluorescent and incandescent lighting as is shown by the increased growth when higher PPFD levels were obtained with a combination of multivapor and sodium lamps.
Variability of Reflectance Measurements with Sensor Altitude and Canopy Type1
Authors: Daughtry C. S. T. , Vanderbilt V. C. , Pollara V. J.
Published: July 2010

Use of portable, ground‐based sensors for measuring crop reflectance has created a need for comparable and reliable measurement procedures capable of providing calibrated and reproducible canopy reflectance data. In this field experiment we determined how canopy reflectance varies as a function of sensor altitude above the crop and what minimum altitude is needed to acquire repeatable reflectance measurements with a 15 degree field of view instrument. Data were acquired in 1979 on three canopies grown on a Typic Argiaquoll; mature corn (Zea mays L.) planted in 76 cm rows, mature soybeans [Glycine mays (L.) Merr.] planted in 96 cm rows with 71% soil cover, and mature soybeans planted in 76 cm rows with 100% soil cover. Spectral data were acquired using a Landsat band radiometer (Exotech 100) at 10 altitudes ranging from 0.2 to 10 m above the canopy. At each altitude, measurements were taken at 15‐cm intervals along a 2.0 m transect perpendicular to the crop row direction.

The variance of reflectance factor measurements at low altitudes was attributable to row effects which disappeared at higher altitudes where the sensor integrated across several rows. The coefficient of variation of reflectance factor in both visible and near infrared bands decreased exponentially as the sensor was elevated. Systematic sampling (at odd multiples of 0.5 times the row spacing interval) required fewer measurements than simple random sampling over row crop canopies. Extreme care must be exercised in analyzing and interpreting data acquired at sensor altitudes where the diameter of the sensor's FOV at the top of the canopy is smaller than several multiples of the row spacing.
Influence of Water Stress on the Diurnal Exchange of Mass and Energy between the Atmosphere and a Soybean Canopy1
Authors: Baldocchi D. D. , Verma S. B. , Rosenberg N. J. , Blad B. L. , Garay A. , Specht J. E.
Published: July 2010

A micrometeorological‐physiological study was conducted at Mead, Nebr., during the summer of 1980 to examine the diurnal exchanges of mass and energy of well‐watered and water‐stressed soybean (Glycine max (L.) Merr. cv. Harosoy) canopies and to relate these exchanges to environmental and physiological variables. Data are presented for 2 clear days when the canopy was fully‐developed. Measurements of CO2, latent heat and sensible heat flux were made using the Bowen‐ratio energy balance technique. The soil of the area is a Sharpsburg silty clay loam (a fine, montmorillonitic, mesic Typic Argiudoll). Water stress greatly influenced the partitioning of available energy between latent and sensible heat flux. When the crop was well‐watered, sensible heat (H) was directed toward the crop and caused latent heat exchange (LE) to exceed net radiation (Rn). When the crop was water stressed, only two‐thirds of Rn was consumed as LE; the remainder was converted into sensible heat. Since both Rn and vapor pressure deficit were greater on the day when the crop was water‐stressed, stomatal closure appears to have been the primary cause of the reduction in LE.

Carbon dioxide exchange was not sensitive to water stress in the morning but was severely limited by such stress during midday. The midday reduction in CO2 exchange appears to have been caused by a combination of high stomatal resistance limiting CO2 diffusion to the cell chloroplasts and low leaf water potential coupled with high air temperature affecting the enzymatic reactions associated with photosynthesis. Water use efficiency (defined in terms of the CO2‐water flux ratio) was greater when the crop was well‐watered than when it was stressed for water. A combination of water stress, a large vapor pressure deficit, and high air temperature reduced the CO2‐water flux ratio.