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United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

1992

Articles 1 - 14 of 14

Full-Text Articles in Life Sciences

Simulating Winter Wheat Shoot Apex Phenology , G. S. Mcmaster, Wallace Wilhelm, J. A. Morgan Nov 1992

Simulating Winter Wheat Shoot Apex Phenology , G. S. Mcmaster, Wallace Wilhelm, J. A. Morgan

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Simulation models are heuristic tools for integrating diverse processes and help to increase our understanding of complex processes and systems. Models that predict crop development can serve as decision-support tools in crop management. This paper describes a phenology simulation model for the winter wheat shoot apex and reports validation and sensitivity analysis results.

The complete developmental sequence of the winter wheat shoot apex is quantitatively outlined and correlated with commonly recognized phenological growth stages. The phyllochron is used to measure the thermal time between most phenological growth stages, thereby increasing the flexibility over the growing degree-day (GDD) and photothermal approaches. …

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Low Pressure Center Pivot And Soil Management Effects On Runoff, L. N. Mielke, J. R. Gilley, Wallace Wilhelm Nov 1992

Low Pressure Center Pivot And Soil Management Effects On Runoff, L. N. Mielke, J. R. Gilley, Wallace Wilhelm

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The objective of this research was to determine the influence center-pivot sprinkler irrigation methods in combination with tillage practices for corn (Zea mays L.) have on surface runoff of irrigation and rainfall. A center pivot irrigation machine was redesigned to apply water by high-pressure-impact (HPI), low-pressure-impact (LPI), and low-pressure-spray (LPS) nozzles. The center-pivot was a standard 10-tower machine, 395 meters in length and 38.4 meters tower spacing. Three tillage systems were used -- till-plant (T), disk (D), and subtill (S) which was till-plant with subsoiling between rows with straight single shanks, 360 mm deep, after last cultivation. The soil …

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Simulating Winter Wheat Spike Development And Growth, Gregory S. Mcmaster, Jack A. Morgan, Wallace Wilhelm Nov 1992

Simulating Winter Wheat Spike Development And Growth, Gregory S. Mcmaster, Jack A. Morgan, Wallace Wilhelm

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Mechanistic crop simulation models can aid in integrating and directing research, and in improving farm management strategies. Information derived from recent research on spike development and growth of winter wheat (Triticum aestivum L.) was incorporated into a submodel, SPIKEGRO, and added to an existing model called SHOOTGRO. This manuscript discusses the SPIKEGRO submodel.

SPIKEGRO emphasizes the reproductive functioning of the shoot apex. The complete developmental sequence of the shoot apex is outlined and quantified. All developmental events and growth stages are predicted, most using the phyllochron approach. Spikelet and floret primordium initiation, growth, and abortion; ovule fertilization and growth; …

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Response Of Central Plains Taligrass Prairies To Fire, Fertilizer, And Atrazine, Robert A. Masters, Kenneth P. Vogel, Robert B. Mitchell May 1992

Response Of Central Plains Taligrass Prairies To Fire, Fertilizer, And Atrazine, Robert A. Masters, Kenneth P. Vogel, Robert B. Mitchell

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Tallgrass prairies are an important forage resource in the eastern Central Great Plains. The effect of spring burning, fertilization, and atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine- 2,4-diamine] on standing crop of selected herbaceous species and categories of vegetation was determined in 6 tallgrass prairie environments located near Lincoln and Virginia, Neb., from 1987 through 1989 and 1 site near Bloomfield, Neb., in 1987. The grasslands were in good to excellent condition at the time these studies were conducted. Portions of each site were burned in mid-to late spring, atrazine was applied at a rate of 2.2 kg a.i. ha-1 in late April to …

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Simulating Winter Wheat Production In Three Tillage Systems Using The Nitrogen Tillage Residue Management Model, B. Davidoff, Wallace Wilhelm, Joseph M. Skopp May 1992

Simulating Winter Wheat Production In Three Tillage Systems Using The Nitrogen Tillage Residue Management Model, B. Davidoff, Wallace Wilhelm, Joseph M. Skopp

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Crop production system analysis is necessary to identify tillage and residue management practices that affect crop production. The objective of this study was to evaluate the potential of using the Nitrogen Tillage Residue Management (NTRM) model to evaluate the influence of tillage practices on winter wheat (Triticum aestivum L.) yield. Modifications of the NTRM model were required to simulate winter wheat production. The model was calibrated using site-specific information obtained from a tillage-nitrogen rate experiment conducted at the High Plains Agricultural Laboratory near Sidney, NE, on an Alliance silt loam (fine silty, mixed, mesic Aridic Argiustoll). Model output was …

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Determination Of Root Biomasses Of Three Species Grown In A Mixture Using Stable Isotopes Of Carbon And Nitrogen, H. Wayne Polley, Hyrum B. Johnson, Herman S. Mayeux Jan 1992

Determination Of Root Biomasses Of Three Species Grown In A Mixture Using Stable Isotopes Of Carbon And Nitrogen, H. Wayne Polley, Hyrum B. Johnson, Herman S. Mayeux

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A method is evaluated that employs variation in stable C and N isotopes from fractionations in C and N acquisition and growth to predict root biomasses of three plant species in mixtures. Celtis laevigata Willd. (C3), Prosopis glandulosa Torr. (C3, legume) and Schizachyrium scoparium (Michx.) Nash (C4), or Gossypium hirsutum L. (C3), Glycine max (L.) Merr. (C3 legume), and Sorghum bicolor (L.) Moench (C4) were grown together in separate, three-species combinations.

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Scs Water Surface Profile Model - Wsp2, William H. Merkel, Donald E. Woodward Jan 1992

Scs Water Surface Profile Model - Wsp2, William H. Merkel, Donald E. Woodward

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The Soil Conservation Service (SCS) has revised its mainframe water surface profile model WSP2 and is distributing it as a microcomputer program. WSP2 is used by SCS and others in flood plain management studies and project planning. The model uses the standard step method for computing one-dimensional steady flow profiles for channel and flood plain cross sections and computes backwater at bridges and culverts.

Unique features of WSP2 are described with respect to input data, calculation procedures, user manual, error checking, and output. The use of WSP2 with other SCS hydrologic software is described.

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New Diets For Production Of House Flies And Stable Flies (Diptera: Muscidae) In The Laboratory, Jerome Hogsette Jan 1992

New Diets For Production Of House Flies And Stable Flies (Diptera: Muscidae) In The Laboratory, Jerome Hogsette

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A diet for rearing the house fly, Musca domestica (L.), was developed from feed constituents available on a year-round basis in Gainesville, FL. The diet, called the Gainesville House Fly Diet, performed as well or better than the Chemical Specialties Manufacturers' Association fly larval medium (CSMA) and can be mixed, bagged, and delivered by a local feed mill within 3 d. By adding pelleted peanut hulls 1:1 by volume, the house fly diet becomes suitable for rearing the stable fly, Stomoxys calcitrans (L.). Use of these diets and the economics involved are discussed further.

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Comparative Toxicity Of Aqueous Solutions Of Boric Acid And Polybor 3 To House Flies (Diptera: Muscidae), Jerome Hogsette, Philip Koehler Jan 1992

Comparative Toxicity Of Aqueous Solutions Of Boric Acid And Polybor 3 To House Flies (Diptera: Muscidae), Jerome Hogsette, Philip Koehler

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

LC50s and LT50s of boric acid and polybor formulated in water and 10% sucrose were determined for 3- to 5-d-old adult house flies, Musca domestica (L.), of mixed sex. Differences between boric acid and polybor toxicities were significant in 10% sucrose, but not in water. However, borates formulated in water had significantly lower LC50S than those formulated in 10% sucrose. Rate of kill for formulations in water was fairly uniform over time, whereas mortality from sucrose formulations was not observed until 17 h after treatment. Reasons for differences in the manifestation of mortality and …

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Spontaneous Tetraploid Melons, Perry E. Nugent, Dennis T. Ray Jan 1992

Spontaneous Tetraploid Melons, Perry E. Nugent, Dennis T. Ray

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Since 1968, three spontaneous 4x melons (Cucumis melo L.) plants were discovered in our field or greenhouse plantings. Two were found in the cultivar Planters Jumbo and one in the virescent marker C879-52. Each of these 4x plants had rounded cotyledons, shorter internodes, thicker stems and leaves, more hairs, and smaller fruits, with larger stem and blossom scars, than their 2x counterparts. Also, their flowers, pollen grains, stomates, and seeds were larger. The discovery of a 4x virescent plant in 1987 allows easier germplasm transfer between ploidy levels. Morphological characteristics of 2x and 4x melons will allow identification without …

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Comparison Of Restriction Fragment Length Polymorphisms In Chloroplast Dna Of Five Leafy Spurge (Euphorbia Spp.) Accessions, Scott Nissen, Robert A. Masters, Donald Lee, Martha Rowe Jan 1992

Comparison Of Restriction Fragment Length Polymorphisms In Chloroplast Dna Of Five Leafy Spurge (Euphorbia Spp.) Accessions, Scott Nissen, Robert A. Masters, Donald Lee, Martha Rowe

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Chloroplast DNA (cpDNA) restriction fragment length polymorphisms (RFLPs) were analyzed to assess genetic variation and relatedness among selections of North American and Eurasian leafy spurge. Leafy spurge accessions from Nebraska, Montana, Russia, Italy, and Austria were evaluated. Total DNA was extracted from young leaves and digested with the restriction endonuclease, EcoRI. CpDNA fragment patterns were determined by Southern blot analysis using mung bean cpDNA probes. Colinearity between the mung bean and leafy spurge chloroplast genomes was indicated by the observation that common fragments were hybridized by adjacent probes. Minimum estimates of chloroplast genome size for the five leafy spurge …

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Loop Rating Curves From Goodwin Creek, Roger A. Kuhnle, Andrew J. Bowie Jan 1992

Loop Rating Curves From Goodwin Creek, Roger A. Kuhnle, Andrew J. Bowie

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Two types of hysteresis loops have been observed on Goodwin Creek: those with a greater flow depth for a given discharge on the falling limb of the hydrograph (type 1) and those with a greater flow depth for a given discharge on the rising limb of the hydrograph (type 2). Causes of these 2 loop types are investigated in this paper.

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Effects Of Weaning On Concentrations Of Inhibin In Follicular Fluid And Plasma Of Sows, W. E. Trout, J. H. Killen, R. K. Christenson, B. D. Schanbacher, J. J. Ford Jan 1992

Effects Of Weaning On Concentrations Of Inhibin In Follicular Fluid And Plasma Of Sows, W. E. Trout, J. H. Killen, R. K. Christenson, B. D. Schanbacher, J. J. Ford

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Changes in plasma and follicular fluid concentrations of inhibin were examined in sows after weaning at 28-32 days post partum. From 0 to 48 h after weaning, inhibin concentrations were 200-300times higher in follicular fluid from small ( < 4 mm) and medium-large( ≥4 mm) follicles than in ovarian venous plasma. Inhibin concentrations increased in follicular fluid from medium-large follicles at 24 and 48 h after weaning; concentrations in ovarian venous plasma were positively correlated with the number of medium-large follicles (r= 0·40)and with ovarian venous plasma concentrations of oestradiol (r= 0·61).Blood samples were collected for 30 days from sows (n=6) that exhibited oestrus within 5 days after weaning and from sows (n=5) that remained anoestrous for 11 days after weaning. Plasma inhibin concentrations rose in oestrous and anoestrous sows by 12 h and continued to rise for 60 h after weaning. Plasma inhibin concentrations rose further and were higher at 3·5-4·5days after weaning in oestrous sows than in sows that remained anoestrous. After oestrus, plasma inhibin concentrations declined. At weaning, plasma concentrations of follicle-stimulating hormone (FSH) were higher in sows that subsequently exhibited oestrus than in sows that remained anoestrous. After weaning, plasma concentrations of FSH declined in both groups, reached a nadir at 2·5days, and increased gradually in anoestrous sows; oestrous sows exhibited an FSH surge at oestrus. Plasma FSH returned to preweaning concentrations in both groups of sows at Days 7-8.The results demonstrated dynamic changes in plasma concentrations of FSH and inhibin in sows after weaning; an inverse relationship of these, with the exception during the preovulatory surge of FSH, typifies the porcine oestrous cycle.

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Autoseparation Method For Harvesting House Fly (Diptera: Muscidae) Pupae Of Known Age, Jerome Hogsette Jan 1992

Autoseparation Method For Harvesting House Fly (Diptera: Muscidae) Pupae Of Known Age, Jerome Hogsette

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Postfeeding larvae of Musca domestica (L.) were allowed to crawl from the larval rearing medium into sand-filled collection containers to pupate. By separating postfeeding larvae and pupae from the sand at predetermined intervals, the approximate time of pupation and the pupal age could be determined. More postfeeding larvae were collected in fine, wet sand than in coarse, dryer sand. Whether or not the sand was tightly packed into collection containers was unimportant, and fly mortality was not increased by the sand-collection method. Uses for the system and implications of the results are discussed.

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