Rolling soybeans is probably not a common practice in Illinois with the deep prairie soils and relatively level terrain. But it has its benefits and ups and downs and is practiced in states like North and South Dakota, and areas of western Minnesota and northwestern Iowa.
Ground rolling prepares the field for harvesting by leveling fields, pushing rocks into the soil, shattering corn root balls and stumps, and smoothing the seedbed. Growers can lower their platforms closer to the ground with less risk of picking up dirt, clods or rocks. This was a big deal until draper heads came on the market. Those heads can run closer to the soil surface than a conventional head with an auger.
Another benefit of rolling beans is that dinging the terminal growing point at the top of the plant encourages more node set and branching. You get the same benefit from early planting or supposedly applying Cobra® at V2 or V3. Cobra dings soybean plants and burns leaves. An early application will ding the terminal growing point and supposedly increase branching and pod set. However, applying Cobra that early can be risky to the plant.
If rolling does indeed create more branching and pod set, and produces two more pods with 2.5 beans per pod, that would be equivalent to 4 more bushels per acre. The cost of rolling is less than a bushel per acre and is a fast process with a 60′ to 90′ rolling width at 8 to 10 mph. If rolling does improve final pod set, that would make the practice more beneficial and justifiable. But the evidence that it consistently increases pod set is sketchy at best and mainly theoretical—just like applications of Cobra.
Fields can be rolled before planting, just after planting and up to the V3 leaf stage. A 3-year study by the University of Minnesota showed that beans can be safely rolled up to V3 (third trifoliate). After V3, plant damage can offset any benefit.
A report written by Jodi DeJong-Hughes and Phil Glogoza at the University of Minnesota offers these guidelines:
- “Confine rolling to rocky fields and flat fields with low erosion risk.
- Roll before plants reach the third trifoliate growth stage, or about 3 inches tall. If you roll after emergence, expect some plant injury.
- If you roll erosion-prone fields, roll pre-plant or post-emergence, rather than right after planting, when erosion risk is greatest.
- After emergence, roll in the afternoon during the heat of the day when soybeans are limp. Avoid rolling in the morning or evening, when plants are most rigid.
- Roll only when field conditions are favorable. To reduce the risk of crusting or sealing, don’t roll when the soil is moist.
- After emergence, avoid rolling when plants are damp because they will stick to the tool bar and be pulled out of the soil. Do not roll when it’s windy.
- Consider rolling carefully when there is little crop residue (<20%). The disadvantages may well outweigh any benefits.”
You can read the full report “Rolling soybeans: The Good, the bad, and the injured” by clicking here.
Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at email@example.com.