EFFECT OF ENVIRONMENT ON THE RESPONSE OF MAIZE (Zea maysL.) INBREDS TO HERBICIDE NICOSULPHURON

Field experiments were conducted over two years to characterize maize inbred responses to herbicide nicosulphuron. In the first year of research (1999), 30 maize inbreds were tested (preliminary screening). Based on the first year results, eight inbreds were selected and evaluated in the second year of research (2000). Herbicide nicosulphuron was applied at the permitted (48 g a.i. ha-1) and double (96 g a.i. ha-1) rate when maize plants were at the growth stages with 1-3, 3-5 and 5-7 visible leaves. The effect of herbicide was estimated visually at 14, 30 and 60 days after herbicide application using the ERWS scale. Maize inbreds significantly differed for their tolerance to nicosulphuron. All inbreds were more sensitive to nicosulphuron in the dry growing season of 2000 compared to the normal growing conditions of 1999. However, tested inbreds varied greatly in response to nicosulphuron depending on growing conditions. The application of double rate tended to increase inbred sensitivity to herbicide applied. Tested inbreds were more sensitive to nicosulphuron when its application was done at the more advanced maize growth stages.