Life Sciences Commons^™

Native Wildflower Establishment With Imidazolinone Herbicides, Daniel D. Beran, Roch E. Gaussoin, Robert A. Masters

Department of Agronomy and Horticulture: Faculty Publications

Native wildflowers are important components of grassland communities and low-maintenance wildflower seed mixtures. Weed interference limits successful establishment of native wildflowers from seed. Experiments were conducted to determine the influence of the imidazolinone herbicides imazethapyr, imazapic, and imazaquin on the establishment of blackeyed susan (Rudbeckia hirta L.), upright prairieconeflower [Ratibida columnifera (Nutt) Woot. and Standl.], spiked liatris [Liatris spicata (L.) Willd.], blanket flower (Gaillardia aristata Pursh.), purple coneflower [Echinacea purpurea (L.) Moench.], and spotted beebalm (Monarda punctata L.). Wildflower response to the herbicide treatments was variable and appeared to be influenced by the level …

A Review Of Issues Pertaining To Transgenic Turfgrasses, Paul G. Johnson, Terrance P. Riordan

Department of Agronomy and Horticulture: Faculty Publications

Recombinant DNA technology is a rapidly growing field in plant and animal breeding. This technology involves the transfer of pieces of DNA, or genes, regardless of the organisms involved or how they are related. Transformation procedures in plants were first developed for important crop and model plant systems. Although turfgrass management and production is one of the fastest growing areas of agriculture, genetic transformation of turfgrasses lags behind that of many other important crop plants. Turfgrasses are becoming more important primarily because of their association with the ever-increasing urban population. The size of the turfgrass seed market is second only …

Ecophysiological Characteristics Of Four Maize Hybrids And Abutilon Theophrasti, John L. Lindquist, David A. Mortensen

Department of Agronomy and Horticulture: Faculty Publications

Combining empirical research with simulation modeling may improve our understanding of the dynamics of crop:weed competition and for testing hypotheses on the importance of specific traits for enhancing crop performance in mixtures. Two field experiments were conducted to quantify and compare estimates of traits important for radiation interception and utilization in four maize hybrids and Abutilon theophrasti grown in monoculture. Early leaf area growth rate did not vary among maize hybrids within a year, but varied among years. The response of CO₂ assimilation rate to absorbed radiation and leaf nitrogen content did not differ among hybrids. Abutilon theophrasti and …

Stability Of Corn (Zea Mays)- Foxtail (Setaria Spp.) Interference Relationships, John L. Lindquist, David A. Mortensen, Philip Westra, W. J. Lambert, Thomas T. Bauman, Jason Fausey, James Kells, Steven Langton, R. Gordon Harvey, Brett H. Bussler, Kevin Banken, Sharon Clay, Frank Forcella

Department of Agronomy and Horticulture: Faculty Publications

Variation in interference relationships have been shown for a number of crop-weed associations and may have an important effect on the implementation of decision support systems for weed management. Multiyear field experiments were conducted at eight locations to determine the stability of corn-foxtail interference relationships across years and locations. Two coefficients (I and A) of a rectangular hyperbola equation were estimated for each data set using nonlinear regression procedures. The I and A coefficients represent percent corn yield loss as foxtail density approaches zero and maximum percent corn yield loss, respectively. The coefficient I was stable across years …

Measurement Of Sorghum Stalk Strength Using The Missouri-Modified Electronic Rind Penetrometer, Jeffrey F. Pedersen, J. J. Toy

Department of Agronomy and Horticulture: Faculty Publications

Resistance to lodging is critical in sorghum [Sorghum bicolor (L.) Moench] grown for grain, yet adequate tools for plant breeders to assess this character at or before anthesis have not been developed. The objective of this study was to evaluate whether an electronic penetrometer previously shown to be an effective tool for measuring stalk strength in maize (Zea mays L.) could be usedd to differentiate among grain sorghum hybrids. Entries in three commercial grain sorghum hybrid trials were evaluated for rind penetrometer resistance (RPR) of the peduncle, the lower stalk anthesis and the lower stalk at maturity. Actual …

Evaluation Of Switchgrass Rhizosphere Microflora For Enhancing Seedling Yield And Nutrient Uptake, John J. Brejda, Lowell E. Moser, Kenneth P. Vogel

Department of Agronomy and Horticulture: Faculty Publications

Many rhizosphere microorganisms enhance nutrient uptake and plant growth, but their effectiveness can vary with host species and with genotype within species. This study evaluated the effectiveness of rhizosphere microflora indigenous to the rhizosphere of switchgrass (Panicum virgatum L.) for enhancing seedling yield and nutrient uptake. Switchgrass roots and rhizosphere soil were collected from native prairies and seeded stands in Nebraska, Kansas, Iowa, Missouri, Virginia, and North Carolina. Seedlings of four switchgrass cultivars were inoculated with root fragments and rhizosphere soil from each collection, fertilized with a nutrient solution, and gown in steamed sand for 12 wk in a …

Growth Responses Of Warm-Season Tall Grasses To Dormant Season Management, Walter H. Schacht, Alexander J. Smart, Bruce Anderson, Lowell E. Moser, Richard J. Rasby

Department of Agronomy and Horticulture: Faculty Publications

A study on Conservation Reserve Program (CRP) land was established in southeastern Nebraska to determine the effect of dormant-season management on subsequent-year growth rates and yields of tallgrasses. The purpose of the management practices was removal of standing dead material and litter that negatively impact plant growth and grazing efficiency. Treatments consisted of a control with no residue manipulation and 5 residue manipulation practices including (1) October shredding and leaving residue; (2) October haying; (3) October intensive grazing; (4) March intensive grazing; and (5) spring prescribed burning. The study was conducted in 1994195 and 1995/96 on a switchgrass (Panicum …

Morphological Development Of 2 Warm-Season Grasses In The Nebraska Sandhills, J. R. Hendrickson, Lowell E. Moser, K. J. Moore, Steven S. Waller

Department of Agronomy and Horticulture: Faculty Publications

Morphological development of grasses has numerous implications to rangeland management including the timing and amount of herbivory. The objective of this study was to quantify the developmental morphology of prairie sandreed [Calamovilfa longifolia (Hook.) Scrihn.] and sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fem.] tiller populations. Tier populations of these 2 grasses were studied for 2 years in the Nebraska Sandhills. Plant development was evaluated using a growth staging system which quantifies the development of tiller populations. A morphological growth index for each species was calculated from either the weighted average of tiller numbers reported as mean stage …

Prediction Of Leaf:Stem Ratio In Grasses Using Near Infrared Reflectance Spectroscopy, Alexander J. Smart, Walter H. Schacht, Jeffrey F. Pedersen, Daniel J. Undersander, Lowell E. Moser

Department of Agronomy and Horticulture: Faculty Publications

Leaf:stem ratio of grass stands is an important factor affecting diet selection, quality, and forage intake. Estimates of leaf:stem ratios commonly are based on a labor intensive process of hand separating leaf and stem fractions. Near infrared reflectance spectroscopy (NIRS) has been used successfully to predict forage quality and botanical composition of vegetation samples. The objective of this study was to evaluate the use of NIRS to predict leaf:stem ratios in big bluestem (Andropogon gerardii Vitman), switchgrass (Punicum virgatum L.), and smooth bromegrass (Bromus inermis Leyss.). A total of 72 hand-clipped samples of each species was taken …

Waxy Wheats: Origin, Properties, And Prospects, Robert A. Graybosch

Department of Agronomy and Horticulture: Faculty Publications

Starch amylose is synthesized through the activity of the granule-bound starch synthase (GBSS). In wheat (Triticum aestivum L. ), there are three structural genes encoding iso- forms of GBSS. Naturally occurring mutations (null alleles) resulting in the loss of one or more GBSS isoforms have recently been identified. The presence of one or two GBSS null alleles results in the production of starch with reduced amylose content. Reduced amylose wheats have been termed `partial waxy'. Wheats with three GBSS null alleles produce essentially amylose-free, or waxy, starch. Partial waxy wheats are sources of flours with optimal quality characteristics in …

Baking Quality Of Hard Winter Wheat: Response Of Cultivars To Environment In The Great Plains, C. J. Peterson, R. A. Graybosch, D. R. Shelton, P. Stephen Baenziger

Department of Agronomy and Horticulture: Faculty Publications

Inconsistency of wheat end-use quality has long been a problem for the milling and baking industries, which require high levels of uniformity for modern, high speed, processing. Extensive research was conducted to characterise genetic, environmental, and biochemical factors that contribute to variation in wheat quality. Samples from 17 locations of trials with 30 cultivars grown over two years were evaluated for grain quality, milling yield, mixograph parameters and baking properties. Protein quality and composition of flour samples were determined by SDS sedimentation and size-exclusion chromatography. Test sites were monitored for soil fertility, and meteorological data was collected hourly during grain …

Weather And Management Impact On Crop Yield Variability In Rotations, Charles Yamoah, Gary E. Varvel, Charles Francis, William Waltman

Department of Agronomy and Horticulture: Faculty Publications

Crop rotations are designed to increase productivity and reduce costs. These advantages are contingent upon favorable weather and require appropriate management. Unpredictable weather poses risks to dryland crop production. Information on how weather affects yields in different cropping systems and how farmers could respond with management would help minimize risk and stabilize yield and income. We evaluated the effects of preseason and growing season weather variability on continuous and sequential cropping of corn, sorghum, and soybean in a 12-yr span, and suggest how management decisions could influence cropping system performance.
Models of different levels of sophistication have been developed to …

Growth Traits Among Sorghum Genotypes In Response To Aluminum, J. H. Bernal, R. B. Clark

Department of Agronomy and Horticulture: Faculty Publications

Aluminum (Al) has many detrimental effects on plant growth, and shoots and roots are normally affected differently. A study was conducted to determine differences among sorghum [Sorghum bicolor (L.) Moench] genotypes with broad genetic backgrounds for growth traits of plants grown at 0,200,400,600, and 800 uM Al in nutrient solutions (pH 4.0). Genotypes were categorized into "Al-sensitive", "intermediate Al-tolerant", "Al-tolerant", and SC 283 (an Al-tolerant standard). As Al increased, shoot and root dry matter (DM), net main axis root length (NMARL), and total root length (TRL) became lower than controls (0 Al). Aluminum toxicity and/or nutrient deficiency symptoms become …

Statistical Design And Analysis Of Producer/Consumer Evaluations To Assess Plant Quality, Walter W. Stroup, Stacy A. Adams, Ellen Paparozzi

Department of Agronomy and Horticulture: Faculty Publications

Researchers in ornamental horticulture often want to assess the effects of experimental treatments on plant quality. Producers often use the results of such experiments to establish the minimum level of a treatment, for instance, the amount of a growth regulator or a nutrient, such as nitrogen, needed to achieve desired plant quality. For edible plants, quality can be quantified objectively by using numeric response variable such as yield or nutritional content. However, for ornamental plants, quality depends on aesthetic appeal and consumer acceptance, traits which are subjective and qualitative.

Statistical models for the design and analysis of experiments involving numeric …

Seedbank Characteristics Of A Nebraska Sandhills Prairie, Claudio J. Perez, Steven S. Waller, Lowell E. Moser, James L. Stubbendieck, Allan A. Steuter

Department of Agronomy and Horticulture: Faculty Publications

Evaluating seedbank ecology is critical for understanding plant community development and successional patterns and for identifying factors regulating population dynamics. The relationships among seedbank composition, seedbank depth, seed dormancy, and vegetative expression were evaluated for a range site on a Valentine fine sand soil (mixed, mesic Typic Ustipsamments) in the Sandhills Prairie. Twenty soil samples were collected at each of 2 depths (0 to 5, 15 to 20 cm) in early June 1990 and 1991 from 12 macroplots (32 X 32 m) representing 3 range condition classes. A seed extraction and germination trial was conducted to determine the diversity, size, …

Tiller Demographics And Leaf Area Index Of Four Perennial Pasture Grasses, Robert B. Mitchell, Lowell E. Moser, Kenneth J. Moore, Daren D. Redfearn

Department of Agronomy and Horticulture: Faculty Publications

Developing grazing systems requires basic information on the growth and development of adapted species. The objective of this field study was to determine seasonal tiller demographics and leaf area index (LAI) of intermediate wbeatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey], smooth bromegrass (Bromus inermis Leyss.), switchgrass (Panicum virgatum L.), and big bluestem (Andropogon gerardii Vitman) tiller populations. This study was conducted in 1992 and 1993 near Mead, NE, on a silty clay loam soil (Typic Argiudoll) as a randomized complete block. Monocultures were harvested six times each year for tiller demographics. Additionally, mean stage count …

The ‘‘Foliage Is The Fruit’’ Hypothesis: Complex Adaptations In Buffalograss (Buchloe Dactyloides), John Ortmann, Walter H. Schacht, James L. Stubbendieck, Dennis R. Brink

Department of Agronomy and Horticulture: Faculty Publications

Buffalograss (Buchloe dactyloides) has been described as an excellent fit for Janzen’s ‘‘Foliage is the Fruit’’ (FF) hypothesis, which suggests that large grazing animals ingest and later disperse seeds of some herbs when consuming their foliage. We tested this hypothesis by feeding buffalograss burs and legume seeds to ruminally fistulated beef steers. Our objectives were to determine (1) rumen residence times of buffalograss burs, free buffalograss caryopses and legume seeds; (2) total tract residence times for the three types of propagules; (3) percentage propagule survival after passage and (4) germinability of fed and unfed burs and caryopses. Bur …

Mycorrhizal Colonization And Nutrition Of Wheat And Sweet Corn Grown In Manure-Treated And Untreated Topsoil And Subsoil, David D. Tarkalson, Von D. Jolley, Charles W. Robbins, Richard E. Terry

Department of Agronomy and Horticulture: Faculty Publications

Dry bean yields (Phaseolus vulgaris L.) were raised to similar levels as the topsoil by manure application to eroded or leveled Portneuf silt loam soil (coarse-silty mixed mesic Durixerollic Calciorthid). Only soil organic matter and zinc (Zn) content of leaf tissue were correlated with improved yields. Manure application increased mycorrhizal colonization and Zn uptake in pot experiments with dry bean which would explain the increased yields in the field. A field study was conducted to see if similar effects of manure and mycorrhizal colonization could be observed in field grown spring wheat (Triticum aestivum L.) and sweet corn …

Tolerance And Velvetleaf (Abutilon Theophrasti) Suppressive Ability Of Two Old And Two Modern Corn (Zea Mays) Hybrids, John L. Lindquist, David A. Mortensen

Department of Agronomy and Horticulture: Faculty Publications

Improved crop tolerance and weed suppressive ability are tactics that may reduce the negative effect of weeds on crop yield. Irrigated field experiments were conducted to compare leaf area index (LAI), intercepted photosynthetic photon flux (PPF), and relative tolerance and velvetleaf suppressive ability among two old (circa1 940) and two modern corn hybrids. Each hybrid was grown in monoculture and in mixture with velvetleaf at 1, 4, 16, and 40 plants m^-1 row. Plants were periodically harvested in monoculture plots to obtain estimates of corn LAI, and PPF interception was measured. Variation in hybrid tolerance to velvetleaf competition for …

Economic Importance Of Managing Spatially Heterogeneous Weed Population, John L. Lindquist, J. Anita Dieleman, David A. Mortensen, Gregg A. Johnson, Dawn Y. Wyse-Pester

Department of Agronomy and Horticulture: Faculty Publications

Three methods of predicting the impact of weed interference on crop yield and expected economic return were compared to evaluate the economic importance of weed spatial heterogeneity. Density of three weed species was obtained using a grid sampling scheme in 11 corn and 11 soybean fields. Crop yield loss was predicted assuming densities were homogeneous, aggregated following a negative binomial with known population mean and k, or aggregated with weed densities spatially mapped. Predicted crop loss was lowest and expected returns highest when spatial location of weed density was utilized to decide whether control was justified. Location-specific weed management resulted …

Nebraska Range Shortcourse: A Successful Approach To Continuing Education, Daniel R. Vaughn, Anthony D. Watson, Lowell E. Moser, Walter H. Schacht

Department of Agronomy and Horticulture: Faculty Publications

Casual visitors to Nebraska rarely see the diversity of the 23 million acres of its rangeland. The state boasts of its nonparalleled range beef cattle industry which relies heavily on the Sandhills, a seemingly endless expanse of grass-covered dunes. In sharp contrast to the Sandhills, however, is a wide array of landscapes including the pine ridge of northern Nebraska, the sagebrush grassland of the southwestern region, the shortgrass prairie of the panhandle, the highly-dissected loess hills, and wooded river valleys. These landscapes offer a complex mixture of habitats, recreational opportunities, rangeland products, and management challenges. People with varied education and …

Morphological Development Of Switchgrass As Affected By Planting Date, Alexander J. Smart, Lowell E. Moser

Department of Agronomy and Horticulture: Faculty Publications

Late-spring and early-summer plantings of warm-season grasses often fail, due to dry soil conditions and competition from annual grass and broadleaf weeds. The objective of this study was to compare the morphological development of switchgrass (Panicum virgatum L.) planted in early, mid, and late spring in eastern Nebraska. This study was conducted in 1994 and 1995 at Lincoln, NE, on a Kennebec silt loam (fine-silty, mixed, mesic Cumulic Hapludolls). 'Blackwell' and 'Trailblazer' switchgrass were planted in mid-March, late April, and late May using a single-row, precision grass-seed cone planter to a depth of 0.6 to 1.3 cm at 98 …

Predicting Developmental Morphology In Switchgrass And Big Bluestem, Rob B. Mitchell, Kenneth J. Moore, Lowell E. Moser, John O. Fritz, Daren D. Redfearn

Department of Agronomy and Horticulture: Faculty Publications

Switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) are important warm-season grasses in livestock production systems in the central and eastern USA. The objectives of this study were to quantify the morphological development of ‘trailblazer’ switchgrass and 'Pawnee' big bluestem and to evaluate day of the year (DOY) and growing degree day (GDD) as predictors of switchgrass and big blnestem morphological stage. Pure stands of each species were sampled at weekly intervals in 1990 and 1991 at Mead, NE, and classified as to mean stage count (MSC) and mean stage weight (MSW). Prediction equations for MSC …

Relationships Between In Situ Protein Degradability And Grass Developmental Morphology, R. B. Mitchell, D. D. Redfearn, Lowell E. Moser, R. J. Grant, K. J. Moore, B. H. Kirch

Department of Agronomy and Horticulture: Faculty Publications

The objective of this research was to determine the relationships between the morphological development and in situ ruminally degradable protein (RDP), ruminally undegradable protein (RUP), and microbial protein of two cool season grasses (intermediate wheatgrass and smooth bromegrass) and two warm season grasses (switchgrass and big bluestem). The initial growth of grass tillers grown near Mead, Nebraska was clipped at ground level six times during the 1992 growing season and morphologically classified. Mean stage was calculated. Forage was ground to pass a 2-mm screen and was incubated in ruminally fistulated steers for 16 h. The RUP was adjusted for microbial …

Leaf Nutritive Value Related To Tiller Development In Warm-Season Grasses, J. R. Hendrickson, Lowell E. Moser, K. J. Moore, Steven S. Waller

Department of Agronomy and Horticulture: Faculty Publications

Assessing nutritive value of key grass species in relation to plant development is essential for producers to efficiently manage livestock enterprises. Changes in nutritive value for tiller populations of 2 common Nebraska Sandhills grasses, prairie sandreed [Calamovilfa longifolia (Hook.) Scribn.] and sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.], in response to morphological development was evaluated at the Gudmundsen Sandhills Laboratory (GSL) during the 1990 and 1991 growing seasons. Morphological development was determined on a 40 to 60-tiller sample from each block (12 blocks in 1990 and 8 blocks in 1991) at ten-day intervals using a comprehensive staging …

Chlorophyll Meter And Stalk Nitrate Techniques As Complementary Indices For Residual Nitrogen, Gary E. Varvel, James S. Schepers, Dennis D. Francis

Department of Agronomy and Horticulture: Faculty Publications

An irrigated monoculture corn and soybean-corn cropping systems study with cropping system as the first split, corn hybrid as the second split, and N fertilizer rate as the final split in four replications was used. Four commercially available Pioneer brand corn hybrids (3162, 3379, 3394, and 3417) were evaluated in both cropping systems. Nitrogen fertilizer as ammonium nitrate was broadcast at rates of 0, 45, 90, 135, and 180 lb N/acre in 1991 and 1992 and 0, 56, 112, 168, and 224 lb N/acre in the 1993 and 1994 growing seasons.

Fractal Analysis Of Temporal Yield Variability Of Crop Sequences: Implications For Site-Specific Management, Bahman Eghball, Gary E. Varvel

Department of Agronomy and Horticulture: Faculty Publications

Characterizing spatial and temporal variability is important in site-specific or long-term studies to evaluate the effects of different management systems on crop performance. Long-term experiments offer unique possibilities to study the effects of management practices on crops and soils over time. The objective of this study was to characterize temporal grain yield variability of seven crop sequences using fractal analysis and to determine whether temporal or spatial variability dominated the grain yield variability. Three crops of corn (Zea mays L .), soybean [Giycine max ( L.) Merr.], and sorghum [Sorghum bicolor (L.) Moench] were studied from 1975 …

Soil Temperature And Fumigation Effects On Plant Phosphorus Uptake And Related Microbial Properties, Dennis L. Mccallister, L. A. Jawson, M. D. Jawson

Department of Agronomy and Horticulture: Faculty Publications

Early season problems with growth of corn (Zea mays L.) under cool, wet conditions prompted a study of the effects of soil and environmental conditions on mineralization and plant uptake of phosphorus (P). Our objective was to determine the effect of soil test P, temperature, and soil fumigation on soil P availability and uptake during early corn growth. Corn was grown in growth chambers at temperatures of 14°C or 25°C. Soils were a high-P Hastings silty clay loam (fine, montmorillonitic, mesic Udic Argiustoll) and a low-P Sharpsburg clay loam (fine, montmorillonitic, mesic Typic Argiudoll). Plants grew for up to …

Notes: Forage Yield, Quality, And Fertility Of Sorghum X Sudan Grass Hybrids In A1 And A3 Cytoplasm, Jeffrey F. Pedersen, J. J. Toy

Department of Agronomy and Horticulture: Faculty Publications

Currently, no information is available comparing the agronomic performance of A1 and A3 cytoplasms in sorghum x sudangrass [Sorghumbi color (L.) Moench] hybrids. The objectives of this study were to compare the effects of A1 and A3 cytoplasm on the maturity, fertility, height, forage yield, and forage quality of sorghum × sudangrass hybrids. In 1989, pollen from a bulk of eight sudangrass populations was used to pollinate four sorghum lines that had been male-sterilized in both A1 and A3 cytoplasm. Hybrids were grown at the Univ. of Nebraska Field Laboratory Ithaca, NE, in 1990 and 1991, in a split-plot …

Buffalograss Establishment With Preemergence Herbicides, Jack D. Fry, Roch E. Gaussoin, Dan D. Beran, Robert A. Masters

Department of Agronomy and Horticulture: Faculty Publications

Field studies were conducted at two sites in Nebraska (NEI and NE2) and one site in Kansas (KS) in 1994 to determine the influence of selected preemergence herbicides on establishment of seeded 'Sharp's Improved' buffalograss [Buchloe dactyloides (Nutt.) Engelm.]. Herbicides were applied within 2 days after seeding. Application ofimazethapyr at 0.07 kg·ha^-1 usually resulted in buffalograss seedling density, vigor, and foliar cover that were superior to buffalograss stands where other herbicides were applied. Buffalograss response to AC 263,222 at 0.07 kg∙ha^-1 was variable and appeared to be influenced by level of weed interference. Seedling density and vigor …