| Abstrakt: |
Legumes are important components of grassland communities in North America and have potential to improve grassland productivity and diversity. Weeds can interfere with the establishment of legumes and increase probability of stand failure. Four experiments were conducted from 1994 to 1997 to determine if the imidazolinone herbicides imazethapyr [2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐ethyl‐3‐pyridinecarboxylic acid] and imazapic [(±)‐2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐methyl‐3‐pyridinecarboxylic acid] applied preemergence at 70 g a.i. ha−1could reduce weed interference and improve establishment of seeded grassland legumes. Six native legumes and one introduced legume, crownvetch (Coronilla variaL.), were planted into prepared seedbeds at sites near Mead, NE. Legume response to the herbicides varied among species and sites. Crownvetch, partridgepea [Chamaecrista fasciculata(Michx.) Greene; syn. Cassia chamaecristaL.), and purple prairieclover (Dalea purpureaVent.) exhibited tolerance to both imazethapyr and imazapic in most experiments and their establishment, as indicated by stem density and/or forage yield collected 14 mo after planting, was improved when treated with the herbicides in weedy environments. Imazapic treatment injured leadplant (Amorpha canescensPursh), Canada tickclover [Desmodium canadense(L.) DC.], and roundhead lespedeza (Lespedeza capitataMichx.), resulting in lower stem densities and/or forage yields than when imazethapyr was applied. Based on these findings, preemergence application of imazethapyr and imazapic can be used to reduce weed interference and improve the establishment of certain grassland legumes. |
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