Management of herbicide and fertility levels on weeds and Kentucky bluegrass turf.
In a 4-year trial with Kentucky bluegrass (Poa pratensis), cv. Common, the effects were compared of several herbicides, mostly applied pre-weed-emergence in March each year, either alone or in various combinations, with or without N as ammonium nitrate (AN), isobutylidene diurea (IBDU), ureaformaldehyde (UF) or sulphur-coated urea (SCU) at 3 or 6 kg/are. The addition of N from all sources and at either rate markedly improved the control of large crabgrass (Digitaria sp.) and dandelions (Taraxacum officinale) by all herbicides except MSMA, which gave virtually complete control of these weeds when used alone. With most treatment combinations the effect of N was greater at the higher application rate. MSMA + IBDU, UF or SCU was severely phytotoxic, but when applied alone or + AN the injury was less. Data are also presented on the effects on the incidence of red thread disease (Corticium fuciforme) and on turf quality.