Sunflowers have been a staple crop in South Dakota for decades, with the state ranking second in sunflower production in the U.S. In 2023, South Dakota produced over 817 million pounds of sunflowers (Sandbakken, 2023). However, growing sunflowers comes with its own set of challenges, including pest and pathogen issues, like the red sunflower seed weevil and Phomopsis stem canker (Varenhorst 2023; Bush et al. 2019). These problems have been exacerbated by the increase in sunflower acreage and the development of pyrethroid insecticide resistance. In addition to pest pressures, sunflower markets have faced a downturn since 2022, prompting farmers to consider alternative broadleaf crops.
Warm-season broadleaf crops, such as sunflowers, also present challenges related to soil health. After harvest, the short time window to establish cover crops or try relay cropping makes it difficult to prevent soil erosion, especially in dry conditions. Moreover, sunflowers are heavy users of both water and nitrogen, which can strain the subsequent crop. Broadleaf crops generally produce less residue compared to grasses, which can undermine efforts to build organic matter and retain soil moisture. To address these issues, farmers are encouraged to rotate different types of broadleaf crops (both cool-season and warm-season) year-to-year or grow them less frequently (once every four or five years), to mitigate their negative effects.
Alternative Broadleaf Crops
Fortunately, there are alternative broadleaf crops with strong market potential and a better ecological fit for Western South Dakota. One such crop is canola, a cool-season broadleaf that not only has a robust market but also offers environmental benefits, such as improved residue levels. In 2024, canola grown near Martin, South Dakota, yielded 1,500 pounds per acre (30 bushels/acre) and produced 2,500 to 3,500 pounds of dry residue per acre (Figure 1 and Figure 2). This level of residue is significantly higher than that of other broadleaf crops, and with residue standing 10 to 14 inches tall, canola fields are better at capturing snowfall during the fall and winter. This "snow catch" ability can be particularly beneficial in areas where water conservation is crucial.
Other promising crops are camelina or flax, brassica oil crops similar to canola. These crops can be drought-tolerant, have short growing seasons, and are genetically resistant to pests and herbicides. These characteristics make them a strong fit for crop rotations in western South Dakota, where environmental conditions can be harsh. These three alternative broadleaf crops still have limitations however, including the potential for shatter losses in high heat and drought conditions, so careful consideration is needed when making these decisions.
In Summary
In conclusion, choosing the right crop rotation is essential to successful farming, especially in regions like Western South Dakota. Farmers must prioritize water conservation, soil health, and organic matter build up in their rotations. When selecting broadleaf crops, it’s important to focus on intensity (water use), variety (at least three crop types), and profitability. Exploring alternative broadleaf crops, like canola, camelina, or flax, can help meet these goals, ensuring long-term sustainability for farms in the region.