EFFECT OF NITROGEN FERTILIZERS AND OIL ADJUVANTS ON NICOSULFURON EFFICACY

Abstract

Effect of oil adjuvants and nitrogen fertilizers on weed control with nicosulfuron was investigated at two locations in the years 2006 ± 2008. Treatments included nicosulfuron at 60 g ha-1 without adjuvant and at 30 g ha-1 with or without methylated seed oil (MSO) and petroleum (PO) and additionally with and without ammonium nitrate (AMN), urea (U) or urea ± ammonium nitrate liquid fertilizer (UAN). Reduction of nicosulfuron rate from 60 to 30 g ha-1, except Echinochloa crus-galli, significantly decreased Chenopodium album, Viola arvensis, Polygonum convolvulus, and Polygonum aviculare control. E. crusgalli control ranged from 93 to 99% regardless of herbicide and adjuvant treatment. However, addition of oil adjuvants, especially MSO strongly increased weed control, especially when used with AMN and UAN nitrogen fertilizers. Reduction of nicosulfuron rate from 60 to 30 g ha-1 strongly reduced grain yield of maize. However, addition of PO and MSO oil adjuvants, especially MSO applied in a mixture with AMN or UAN nitrogen fertilizers completely overcome this effect and allowed to obtain comparable grain yield of maize as obtained after application of recommended nicosulfuron rate (60 g ha-1).