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Revegetating Spotted Knapweed Infested Rangeland in a Single Entry

Roger L. Sheley, James S. Jacobs and Daniel E. Lucas
Journal of Range Management
Vol. 54, No. 2 (Mar., 2001), pp. 144-151
DOI: 10.2307/4003175
Stable URL: http://www.jstor.org/stable/4003175
Page Count: 8
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Revegetating Spotted Knapweed Infested Rangeland in a Single Entry
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Abstract

Introducing and establishing competitive plants is essential for the successful management of spotted knapweed (Centaurea maculosa Lam.) infested rangeland where a desirable understory is absent. Our objective was to determine a herbicide-mix that would maximize grass establishment in spotted knapweed-cheatgrass (Bromus tectorum L.) bluegrass (Poa pratensis L.) infested rangeland in a single fall application. On 2 sites in Montana, 8 herbicide treatments [none, glyphosate (N-[phosphonomethyl] glycine) at 0.5 kg a.i. ha-1, picloram (4-amino-3,5,6-trichloropicolinic acid, potassium salt) at 0.14 kg a.i. ha-1, picloram at 0.28 kg a.i. ha-1, clopyralid (3,6-dichloro-2-pyrdinecarboxylic acid, monoethanolamine salt) at 0.21 kg a.i. ha-1 plus 2,4-D (2,4-dichlorophenoxyacetic acid) at 1.12 kg a.i. ha-1, picloram at 0.14 kg a.i. ha-1 plus glyphosate at 0.5 kg a.i. ha-1, picloram 0.28 kg ${\rm a}.{\rm i}.{\rm ha}^{-1}$ plus glyphosate at 0.5 kg a.i. ha-1, and clopyralid 0.2 kg a.i. ha-1 plus 2,4-D at 1.12 kg a.i. ha-1 plus glyphosate 0.5 kg a.i. ha-1] and 3 seeded grass species ['Luna' pubescent wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey], bluebunch wheatgrass [Pseudorogneria spicata (Pursh.) Löve], and 'Bozoyski' Russian wildrye [Psathyrostachys junceae (Fisch.) Nevski] were applied in a split-plot design with 4 replications in the late-fall of 1994 and 1995. Spotted knapweed and grass density were measured in 1995, 1996, and 1997, and biomass was measured in 1997 at peak standing crop. Density data were analyzed as a split-split-plot in time, and biomass data were analyzed as a split-plot using analysis of variance. By the end of the study, picloram applied at either 0.14 or 0.28 kg a.i. ha-1 in the late-fall consistently yielded lowest spotted knapweed density and biomass. Initially, glyphosate alone lowered spotted knapweed density and increased grass biomass compared to that of the control. However, glyphosate treated plots had more spotted knapweed and less seeded grass established by the end of the study. 'Luna' pubescent wheatgrass consistently yielded the high test density and biomass of the seeded grasses. We believe a single-entry revegetation program applying picloram in late-fall combined with a fall-dormant seeding will maximize seedling establishment in spotted knapweed infested rangeland. /// La introducción y establecimiento de plantas competitivas es esencial para un manejo exitoso de pastizales infestados con "Spotted knapweed" (Centaurea maculosa Lam.) carentes de vegetación herbácea deseable. Nuestro objetivo fue determinar una mezcla de herbicidas que con una sola aplicación en otoño maximizara el establecimiento de zacates en un pastizal infestado con "Spotted knapweed-Cheatgrass" (Bromus tectorum L.) y "Bluegrass" (Poa pratensis L.). En dos sitios de Montana, a fines de otoño, se aplicaron 8 tratamientos de herbicidas [control (no herbicida), glifosato (N-[fosfonometil] glicine) en dosis de 0.5 kg i.a. ha-1, picloram (sal de potasio, 4-amino-3,5,6 ácido tricloropicolinico) en dosis de 0.14 kg i.a. ha-1, picloram en dosis de 0.28 kg i.a. ha-1 clopiralid, (sal monoetanolamina, 3,6 dicloro-2- ácido pirdinecarboxilico) en dosis de 0.21 kg i.a. ha-1 mas 2,4-D (2,4-ácido diclorofenoxiacetico) en dosis de 1.12 kg i.a. ha-1, picloram en dosis de 0.14 kg i.a. ha-1 mas glifosato en dosis de 0.5 kg i.a. ha-1, picloram en dosis de 0.28 kg i.a. ha-1 mas glifosato en dosis de 0.5 kg i.a. ha-1 y clopiralid en dosis de 0.2 kg i.a. ha-1 mas 2,4-D en dosis de 1.12 kg i.a. ha-1 mas glifosato en dosis de 0.5 kg i.a. ha-1] y se sembraron tres especies de zacates "Pubescent wheatgrass" [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] variedad 'Luna', "Bluebunch wheatgrass" [Pseudorogneria spicata (Pursh.) Löve], y "Russian wildrye" [Psathyrostachys junceae (Fisch.) Nevski] variedad 'Bozoyski'. Se utilizó un diseño experimental de parcelas divididas con 4 repeticiones. En 1995, 1996 y 1997 se midió la densidad de "Spotted knapweed" y zacates, y en 1997, se midió la biomasa de zacate en la época de mayor producción de forraje en pie. Los datos de densidad se analizaron como parcelas divididas en tiempo y la biomasas se analizó como parcelas divididas utilizando análisis de varianza. Al final del estudio el picloram aplicado en dosis de 0.14 y 0.28 kg i.a. ha-1 tuvieron la mas baja densidad y biomasa de "Spotted knapweed". Inicialmente, comparado con el control, el glifosato solo bajo la densidad de "Spotted knapweed" e incremento la biomasa de zacates.sin embargo, al final del estudio, las parcelas tratadas con glifosato tuvieron mas "Spotted knapweed" y menos plantas establecidas de los zacates sembrados. De los zacates sembrados la especie "Pubecent wheatgrass" variedad 'Luna', produjó la mayor densidad de plantas y biomasa. Creemos que un programa de revegetación de una sola vez mediante la aplicación de picloram a fines del otoño en combinación con la siembra en otoño maximizará el establecimiento de plántulas de zacates en los pastizales infestados de "Spotted knapweed".

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