Field studies were used to examine the management strategies of mowing,
herbicide, fertility, and all possible combinations on tall ironweed
populations, weed biomass, and pasture yield at three Kentucky locations.
Mowing was performed in July 2008 and 2009, herbicide was applied in August
2008, and fertilizer was applied in September 2008 and 2009 at all
locations. Weed populations were measured in 2008, 2009, and 2010, and
forage grass, clover, and weed biomass was collected in May or early June of
2009 and 2010. All treatments with herbicide reduced tall ironweed stems by
64% or greater in 2009 at all locations. Mowing alone, fertilizer alone, and
mowing plus fertilizer did not reduce tall ironweed populations, except at
one location where mowing alone reduced tall ironweed stems by 64% in 2009.
Tall ironweed stems were not reduced in 2010 with any treatment at two
locations, but herbicide combined with mowing or fertilizer reduced tall
ironweed stems by 78% at the other location. Tall goldenrod population was
reduced up to 100% by all treatments with herbicide or mowing alone, and
mowing with fertilizer reduced tall goldenrod from 59 to 89%. Treatments did
not reduce horsenettle populations. Herbicide-containing treatments reduced
weed biomass at all locations. Weed biomass did not differ when comparing
all treatments with and without mowing or treatments with or without
fertilizer. Forage grass biomass was greatest with herbicide plus fertilizer
and with the combination of mowing plus herbicide plus fertilizer at all
locations in both years.