Submitted to: Western Society of Weed Science Research Reports
Publication Type: Research notes
Publication Acceptance Date: 12/1/2002
Publication Date: 3/13/2003
Citation: Anderson, R.L. 2003. Improving competitiveness of sunflower with cultural systems. Western Society of Weed Science Research Reports. pp. 125-126. Interpretive Summary: Producers are seeking more effective weed management in sunflowers. Normally, sunflowers are planted in rows spaced 30 inches apart, which leads to a sunflower canopy that is not competitive with weeds. We devised a production system comprised of narrow row spacing (20 inches wide), higher plant population, and fertilizer banding by the seed. We also compared these production systems at two planting dates. This cultural system reduced weed growth 65 to 85%, consequently reducing yield loss due to weeds from 24% with the normal practices used by producers to 6% with the cultural system. A surprising finding in our study was that seed yield with the cultural system was not affected by planting date. Producers often delay planting of sunflowers to help weed control, but sunflowers planted later than normal usually yield less. Thus, the cultural system approach not only improves weed control, but also may widen the window for optimum planting of sunflowers.
Technical Abstract: Weed control in sunflower has been inconsistent in the Central Great Plains. One contributing factor may be that sunflower is not competitive with weeds because it is grown in wide rows (30 inches) and at low plant populations. To strengthen the competitiveness of sunflower, we devised a production system comprised of several cultural practices and compared its impact on weeds with the conventional production system. Common practices for oil-seed sunflower include plant populations of 16,000 plants/ac seeded in 30-inch rows, with N fertilizer applied broadcast. The cultural system was comprised of narrow row spacing (20 inches wide), increased plant population (19,000 plants/ac), and N fertilizer banded adjacent to the seed row. We also compared impact of delayed planting on both systems. The cultural system in sunflower reduced weed density two-fold and weed biomass 60 to 85% compared with the conventional system. Yield loss due to weeds was less than 5% with the cultural system. In contrast, with the conventional system, weeds reduced yield 24% at the early planting date. Delaying planting reduced yield loss due to weeds in the conventional system to only 6%. However, sunflower yielded 17% less in weed-free conditions when planted late with the conventional system. Surprisingly, delayed planting did not reduce yield with the cultural system. We speculate that the cultural system improved growth efficiency of sunflower, which minimized the detrimental effect of late planting. Cultural systems not only improve sunflower's competitiveness with weeds, but also may widen the window for optimum planting.