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Espeland E.K.,Northern Plains Agricultural Research Laboratory | Perkins L.B.,University of Nevada, Reno | Leger E.A.,University of Nevada, Reno
Rangeland Ecology and Management | Year: 2010

Evaluation of the viable seeds in a soil, otherwise known as the seed pool or seed bank, is a crucial component of many weed dynamic and plant ecology studies. Seed bank estimation is used to predict the possibility of future weed infestations in rangelands as well as the nascent native plant diversity within them. However, there is no standardized method of reporting seed bank evaluation techniques, limiting the ability to compare across studies. After sowing known quantities of cheatgrass, Bromus tectorum (L.); brome fescue, Vulpia bromoides (L., S.F. Gray); pigweed, Amaranthus retroflexus (L.); kochia, Kochia scoparia (L. Schrad.); lambsquarters, Chenopodium album (L.); and field pepperweed, Lepidium campestre (L. R. Br.) into sterile soil, we compared two different watering regimes in two soil types to Petri plate germination of these seeds. Seed bank estimations from the emergence method were lower compared to estimations from the Petri plate germination. Top-and-bottom watering increased absolute abundance, and the rank order of abundance among species changed with watering method. Emergence levels were the same between the two soil types. The higher water availability of the top-and-bottom watering method resulted in greater seedling emergence (26.3%±10% SD vs. 9.1%±7.5% SD). Lower emergence compared to germination (62.3%±24.4%) may indicate that emergence is an important postgermination barrier to seedling establishment. While emergence techniques may not accurately portray the volume of seeds in the soil, they may more accurately predict which plants can become established in field conditions. Our different species abundances between watering methods show that multiple emergence methods may need to be employed to forecast a range of future rangeland conditions from the soil seed bank. © Society for Range Management. Source


Lenssen A.W.,Iowa State University | Lenssen A.W.,Northern Plains Agricultural Research Laboratory | Sainju U.M.,U.S. Department of Agriculture | Jabro J.D.,U.S. Department of Agriculture | And 2 more authors.
Agronomy Journal | Year: 2015

Annual cereal forages are resilient in water use (WU), water use effciency (WUE), and weed control compared with grain crops in dryland systems. The combined influence of tillage and management systems on annual cereal forage productivity and WU is not well documented. We conducted a field study for the effects of tillage (no-till and tilled) and management (ecological and conventional) systems on WU and performance of forage barley (Hordeum vulgare L.) and weed biomass in two crop rotations (wheat [Triticum aestivum L.]–forage barley–pea [Pisum sativum L.] and wheat–forage barley–corn [Zea mays L.] –pea) from 2004 to 2010 in eastern Montana. Conventional management included recommended seeding rates, broadcast N fertilization, and short stubble height of wheat. Ecological management included 33% greater seeding rates, banded N fertilization at planting, and taller wheat stubble. Forage barley in ecological management had 28 more plants m–2, 2 cm greater height, 65 more tillers m–2, 606 kg ha–1 greater crop biomass, 3.5 kg ha–1 mm–1 greater WUE, and 47% reduction in weed biomass at harvest than in conventional management. Pre-plant and post-harvest soil water contents were similar among tillage and management systems, but barley WU was 13 mm greater in 4-yr than 3-yr rotation. Tillage had little effect on barley performance and WU. Dryland forage barley with higher seeding rate and banded N fertilization in more diversified rotation produced more yield and used water more effciently than that with conventional seeding rate, broadcast N fertilization, and less diversified rotation in the semiarid northern Great Plains. © 2015 by the American Society of Agronomy, 5585. Guilford Road, Madison, WI 53711. All rights reserved. Source


Jackson M.A.,National United University | Dunlap C.A.,National United University | Jaronski S.T.,Northern Plains Agricultural Research Laboratory
BioControl | Year: 2010

Insect pests persist in a wide-variety of agricultural, arboreal and urban environments. Effective control with fungal entomopathogens using inundation biocontrol requires an understanding of the ecology of the target insect, fungal pathogen, and the insect-pathogen interaction. Historically, the development of production and formulation processes for biocontrol fungi has primarily focused on reducing costs by maximizing the yield of infective propagules, increasing storage stability, and improving product form for ease of application. These goals are critical for commercialization but are often in conflict with environmental and ecological considerations. Critical parameters for selecting a fungal pathogen for use in inundation biocontrol include the cost-effective production of a stable, infective propagule that is suited for use in the environment where the insect must be controlled. Production processes can be manipulated nutritionally and environmentally to produce efficacious propagules or to direct fungal differentiation to propagule forms that may be better suited for use in specific environments. Formulation development must also consider ecological and environmental factors to maximize biocontrol efficacy. A basic understanding of the surface chemistries of the fungal propagule and insect, the interactions between a fungal propagule and the insect cuticle that lead to infection, and the impact of the environment on this interaction can aid in the development of effective formulations. © US Government 2009. Source


Jabro J.D.,Northern Plains Agricultural Research Laboratory
Applied Engineering in Agriculture | Year: 2010

A site-specific controller, hardware and software systems were developed with the capability to switch between either mid-elevation spray application (MESA) or low-energy precision application (LEPA) methods. These systems were field tested and used to manage site-specific irrigations under a linear move sprinkler system and simultaneously varied water application depths by plot as the machine traveled back and forth across the field. The controller and modifications to the water application methods utilized off-the-shelf components as much as possible. The linear move system was modified so that every plot could be irrigated using either MESA or LEPA methods. A programmable logic controller (PLC)-based control system was utilized to activate grouped networks of electric over air-activated control valves. Both the depth and method of irrigation were varied depending on the location of each plot in the field as provided by a low-cost WAAS enabled GPS system mounted on the machine. When not being used, low-cost pneumatic cylinders lifted the LEPA heads above the MESA heads to avoid spray interference when the MESA mode was operating over a specified plot width and length. The control system was used on fifty-six 15- × 24.4-m (50- × 80-ft) plots as well as several other adjacent research projects in which there were a mix of crops and a prescribed set of management experiments. While this particular application was designed specifically for a large, complex agronomic research project to address artificially imposed spatial variability water management, the same controllers, valves and general software could be easily adapted to field scale commercial irrigation. © 2010 AmericanSociety of Agricultural and Biological Engineers. Source


Dalin P.,University of California at Santa Barbara | Dalin P.,Swedish University of Agricultural Sciences | Bean D.W.,Biological Pest Control | Dudley T.L.,University of California at Santa Barbara | And 9 more authors.
Environmental Entomology | Year: 2010

Seasonal adaptations to daylength often limit the effective range of insects used in biological control of weeds. The leaf beetle Diorhabda carinulata (Desbrochers) was introduced into North America from Fukang, China (latitude 44° N) to control saltcedars (Tamarix spp.), but failed to establish south of 38° N latitude because of a mismatched critical daylength response for diapause induction. The daylength response caused beetles to enter diapause too early in the season to survive the duration of winter at southern latitudes. Using climate chambers, we characterized the critical daylength response for diapause induction (CDL) in three ecotypes of Diorhabda beetles originating from 36, 38, and 43° N latitudes in Eurasia. In a field experiment, the timing of reproductive diapause and voltinism were compared among ecotypes by rearing the insects on plants in the field. CDL declined with latitude of origin among Diorhabda ecotypes. Moreover, CDL in southern (<39° N latitude) ecotypes was shortened by more than an hour when the insects were reared under a fluctuating 3515°C thermoperiod than at a constant 25°C. In the northern (>42° N latitude) ecotypes, however, CDL was relatively insensitive to temperature. The southern ecotypes produced up to four generations when reared on plants in the field at sites south of 38° N, whereas northern ecotypes produced only one or two generations. The study reveals latitudinal variation in how Diorhabda ecotypes respond to daylength for diapause induction and how these responses affect insect voltinism across the introduced range. © 2010 Entomological Society of America. Source

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