Differences among Certified Wheat Seedlots in Response to Trifluralin

Injury to wheat from trifluralin [2,6‐Dinitro‐ N,N ‐dipropyl‐4‐(trifluoromethy1)benzenamine] residue occurs under a range of environmental and field conditions and may influence crop stand density, seed quality, and grain yield. The objective of this study was to determine the relationship between seed quality, stand density, and grain yield of wheat ( Triticum aestivum L.) at trifluralin dosages typical of residue levels occurring under western Canadian conditions. Three certified seedlots of ‘Katepwa’ spring wheat designated S1, S2, and S3 were planted into trifluralin‐treated soil under field conditions at Portage la Prairie, Manitoba in 1988 and 1989. All three seedlots had high germination percentages (> 95), however, S1 was darker colored and had a higher thousand‐kernel weight and a greater proportion of large kernels than either S2 or S3. Both cold germination and cold growth tests indicated that S1 and S2 were more vigorous than S3, however no differences in physiological vigor between S1 and S2 were observed. Significant seedlot ✕ trifluralin interactions ( P ≤ 0.05) occurred for crop emergence and seed yield in both years, with S1 being less affected than either S2 or S3 as trifluralin dosages increased. For example, in 1988 where 0.25 kg ha −1 trifluralin was present at seeding, emergence of S1 was reduced by 22% compared to 27% for S2 and 31% for S3 relative to the untreated controls. In 1989, the comparative percentage reductions were 9, 12, and l8%, respectively. Similarly, at 0.25 kg ha −1 , seed yields in plots sown to S1, S2, and S3 were 3, 7, and 13% less than in the untreated plots in 1988; and 5, 7, and 11% less in 1989. Results of this study substantiate that wheat response to soil trifluralin level at seeding can be modified by qualitative and quantitative differences in seed quality.