Interference from crested wheatgrass (Agropyron cristatum [L.] Gaertn.) seedlings is considered a major obstacle to native species establishment in rangeland ecosystems; however, estimates of interference at variable seedling densities have not been defined fully. We conducted greenhouse experiments using an addition-series design to characterize interference between crested wheatgrass and four key native species. Crested wheatgrass strongly interfered with the aboveground growth of Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young), rubber rabbitbrush (Ericameria nauseosa [Pall. ex Pursh] G. L. Nesom & Baird subsp. consimilis [Greene] G. L. Nesom & Baird), and to a lesser extent with bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Lö ve). Alternatively, bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey subsp. californicus [J. G. Sm.] Barkworth) and crested wheatgrass had similar effects on each other's growth, and interference ratios were near 1.0. Results indicate that the native grasses more readily establish in synchrony with crested wheatgrass than these native shrubs, but that once established, the native shrubs are more likely to coexist and persist with crested wheatgrass because of high niche differentiation (e.g., not limited by the same resource). Results also suggest that developing strategies to minimize interference from crested wheatgrass seedlings emerging from seed banks will enhance the establishment of native species seeded into crested wheatgrass-dominated communities. Resumen La interferencia por parte de plántulas de agropiro crestado (Agropyron cristatum [L.] Gaertn.) se considera un obstáculo mayor para el establecimiento de especies nativas en ecosistemas de pastizal natural; sin embargo, las estimaciones de interferencia con densidades variables de plántulas no han sido definidas con precisión. Se condujo un experimento de invernáculo utilizando un diseñ o de series de adición para caracterizar la interferencia entre agropiro crestado y cuatro especies nativas clave. Se observó una interferencia marcada del agropiro crestado sobre el crecimiento aéreo de Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young, Ericameria nauseosa (Pall. ex Pursh) G. L. Nesom & Baird subsp. consimilis (Greene) G. L. Nesom & Baird, y en menor medida con Pseudoroegneria spicata (Pursh) A. Lö ve. Por otra parte, Elymus elymoides (Raf.) Swezey subsp. californicus (J. G. Sm.) Barkworth y el agropiro crestado tuvieron efectos recíprocos similares sobre el crecimiento de cada uno, y la proporción de interferencia fue cercana a 1.0. Los resultados indican que los pastos nativos se establecen con mayor facilidad que los arbustos nativos en sincronía con el agropiro crestado, pero que una vez establecidos, hay mayor probabilidad de que los arbustos nativos coexistan y persistan con el agropiro crestado debido a la diferenciación de nichos (ej., no están limitados por el mismo recurso). Los resultados también sugieren que el desarrollo de estrategias para mini...

Adequate weed control and nutrient supply are critical for successful establishment of fruit trees. This is of particular concern in organic orchard establishment. In order to determine the best approach for establishing peach trees (Prunus persica L.) organically in climates characterized by hot dry summers and cold winters such as the North American Intermountain West, seven organic and three integrated and conventional treatment combinations were established in two first leaf orchards at the USU Kaysville Research Farm, Utah, in 2008 and 2009. Treatments consisted of different tree-row and alleyway mulch and fertilizer combinations.

No abstract

Treerow vegetation abundance and biodiversity were measured in response to six orchard floor management strategies in organic peach in northern Utah for three growing seasons. A total of 32 weed species were observed in the treerow; the most common were field bindweed, dandelion, perennial grasses (e.g., red fescue and ryegrass), clovers, and prickly lettuce. Weed biomass was two to five times greater in unmanaged (living mulch) than in manipulated treatments. Tillage greatly reduced weeds for approximately one month; however, vegetation rebounded midseason. Tillage selected for species adapted to disturbance, such as common purslane and field bindweed. Straw mulch provided equivalent weed suppression to tillage in the early season. Straw required annual reapplication with material costs, labor, and weed-seed contamination (e.g., volunteer grains and quackgrass) as disadvantages. Plastic fabric mulch reduced weeds the most, but had high initial costs and required seasonal maintenance. Weed biomass declined within seasons and across the three years of the study, likely due to tree canopy shading. Neither birdsfoot trefoil nor a perennial grass mixture planted in the alleyways influenced treerow weeds. Our results demonstrate several viable alternatives to tillage for weed management in treerows of organic peach orchards in the Intermountain West.

A two-year study examined weed control in glyphosate resistant sugarbeet with various glyphosate rates and application timings, and glyphosate in combination with residual herbicides or ammonium sulfate (AMS). Treatments that included two or three applications of glyphosate regardless of rate or glyphosate applied once in combination with dimethenamid-p resulted in redroot pigweed, common lambsquarters and hairy nightshade control equal to, or greater than , a standard herbicide program. T he addition of AMS to glyphosate did not affect weed control efficacy. A single application of glyphosate did not provide season long weed control in 1998, but was effective in controlling all weeds but redroot pigweed in 1999. Generally, sugarbeet root yield was similar in plots treated with glyphosate or standard herbicide programs.