Herbicide × Annual Fertility Programs Influence on Creeping Bentgrass Performance
Creeping bentgrass (Agrostis palustris Huds.) is increasing in the use of golf greens in the upper South where heat and drought stress occurs. Research was initiated to determine the effects of annual fertilizer programs on performance of creeping bentgrass treated with spring and fall-applied herbicides. Treatments were arranged in a split-split block with subunits in strips. Fertilizer programs were the main block and the blocks were stripped by spring and fall herbicide treatments. Soil type was an artificial rootzone mix. Creeping bentgrass performed best the first 26 wk of each year when fertilized at the high (490-20-195 kg NPK ha−1 yr−1) fertility level and best the last 26 wk of each year when fertilized at the medium (294-12-124 kg NPK ha−1 yr−1) fertility level. The quality of creeping bentgrass fertilized annually at the low (98-6-52 kg NPK ha−1 yr−1) fertility level was unacceptable. The quality of creeping bentgrass was reduced less at the medium fertility level than at the low fertility level when treated with oxadiazon [3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(l,l-dimethylethyl)-l,3,4-oxadiazol-2-(3H)-one] and bensulide (O,O-bis(l-methylethyl)-S-[2-[(phenylsulfonyl)amino]ethyl]phosphorodithioate] + oxadiazon. Ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methane-sulfonate] applied in the fall 1986 maintained the highest quality ratings at the high fertility level until mid-April when the quality was the same whether fertilized at the medium or high level. In most instances in 1987, the quality of creeping bentgrass treated with ethofumesate at the medium fertility level was equally as good as when treated with the same herbicide but at the high fertility level. When fertilizer by herbicide interaction occurred, creeping bentgrass maintained a higher quality at the medium to high fertility level than at the low fertility level.
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