Optimizing wild oat (Avena fatua) control with ICIA 0604

Wild oat (Avena fatua) control often is an integral management practice in cropping systems that include cereal crops. Experiments were conducted at t wo locations in Saskatchewan (Saskatoon and Scott), Canada, from 1994 to 19 97 to determine the influence of ICIA 0604 rate (50, 100, 150, and 200 g ai /ha), water volume (30, 50, and 100 L/ha), spray mixture pH (unbuffered, cl ose to pH 7.0; reduced, pH 4.0), late morning and evening application times , and sodium bicarbonate concentration of water source (Saskatoon water, ne gligible; Scott water, 695 mg/L) on wild oat fresh weight and wheat (Tritic um aestivum) grain yield. Reducing ICIA 0604 rate below the recommended lab el rate (200 g/ha) increased wild oat fresh weight by 22% and decreased whe at grain yield by 7% when applied with 50 or 100 L/ha of water. Application s with 30 L/ha of water resulted in more wild oat growth (19%) and less whe at yield (6%), regardless of the ICIA 0604 rates. Spray mixture pH or time of application did not modify the effects of ICIA 0604 rate and water volum e on wild oat fresh weight and wheat yield at Saskatoon. At Scott, the nega tive effects of ICIA 0604 rates lower than 200 g/ha applied with 50 or 100 L/ha of water were most apparent when applications were made in the morning , especially with an unbuffered spray mixture. ICIA 0604 applications made in the evening with 50 or 100 L/ha of water resulted in the lowest wild oat fresh weights and greatest wheat yields, regardless of the ICIA 0604 rate or spray mixture pH. Antagonism between sodium bicarbonate in the unbuffere d water from Scott, as indicated by the spray mixture pH effect, and the ti me of application effect were important factors controlling treatment respo nses at Scott. Lower than recommended ICIA 0604 rates often maintained net returns, even though wheat yield responded negatively to reduced ICIA 0604 rates. Understanding the effects of water quality on wild oat control will allow producers to make prudent decisions regarding the optimal application parameters for ICIA 0604.