Land rolling helps conserve moisture and prepare a field for harvest. If conditions are very dry, rolling can improve emergence from moisture conservation and better seed-to-soil contact. Rolling can help level the soil and push rocks into the ground, making it possible for the combine header to do a better job. Small yield gains have been shown when land rolling and are likely the result of better combine header performance, See Table 1, Soybean Yield Response to Land Rolling with a Smooth Roller.
Table 1. Soybean Yield Response to Land Rolling with a Smooth Roller.
| Rolling Method | Yield | Yield Advantage |
| Untreated | 62.6 bu/acre | – |
| Rolling immediately after seeding | 63.5 bu/acre | 0.9 bu/acre |
| V1 Rolling (first trifoliate) | 64.4 bu/acre | 1.8 bu/acre |
| V2 Rolling (second trifoliate) | 63.8 bu/acre | 1.2 bu/acre |
| 2017-2018, 11 Ontario trials, 3 replications. Source: Bohner | ||
Most producers roll immediately after planting, while others wait until the soybeans have emerged. Rolling immediately after planting improves seed-to-soil contact, pushes down rocks, and reduces the likelihood of plant injury. However, it also increases the chance of soil crusting, which hinders soybean emergence. Soybean fields that are not rolled after the drill may emerge more quickly and uniformly if adequate moisture is present. If a heavy rainfall occurs after seeding, rolled fields are more prone to crusting. For this reason, some growers choose to roll after soybean emergence.
Rolling soybeans after emergence does not reduce yields if:
- Fields are rolled during the heat of the day to ensure that soybeans are limp. Rolling during the morning hours, when the soybeans are most turgid (stiff), will increase plant injury.
- Only a smooth roller is used for rolling after soybean emerge, not a packer.
- Soybeans that are just emerging are left to grow until at least the unifoliate stage. Seedlings are vulnerable to being broken off at emergence. Rolling soybeans should not be done past the second trifoliate.
- Fields that have recently received a post emergent herbicide or other plant stress are given a few days to recover before rolling.
Roll a small section of the field and inspect stems to ensure they are not broken. Plants with broken off stems will not recover. Plants that are simply pushed over will stand up again without any lasting damage. If there is any doubt about how much damage is being done to the field roll only a small section and wait a day to inspect how that section recovers. Under normal conditions, soybeans rolled after emergence will completely recover within 24 hours. Tractor tires will do more damage than the actual roller. Be careful not to roll areas twice on headlands and corners. Two passes will cause much more damage than one pass of a roller.