Control Plot (no weeding): weeds are present but were shaded by the faster growing oats and produced only a small biomass
Plot with no oats: Without the faster growing oats to shade them, weeds grew very large. The main weed is ragweed.
|The usual practice for controlling weeds in oats was to harrow a field before seeding so that oats were seeded into a clean seedbed. Then they would be harrowed again after the oats were 7 to 10 cm high. At that point the oats are well rooted and recently germinated weeds are shallow rooted. Harrowing is like a light raking and pulls out the weeds but not the oats.|
In this experiment, part of the field was not harrowed after seeding and part was harrowed once. Then three treatments were set up in 1x1 m plots (5 reps): (i) no additional action, (ii) repeated weeding with a hoe until canopy closure, (iii) oats removed. The bar chart shows the results for plots in the unharrowed strip. The oat yield was reduced by only 9.7% with no weeding. On the other hand, weed yield was reduced more than 6 fold by the crop (compare bar for WEEDS with WDS:NC (weeds in a plot with no oats).
In the once harrowed section, the crop yield was reduced by 4.5% by weeds.
Conclusion: Oats were highly competitive with weeds under these conditions.