Land rolling is one method that can improve harvestability of soybean crops. Rolling evens the soil surface by pushing rocks, soil clods and crop residue into the soil surface. As soybeans are harvested low to the ground due to low pod height, there is a risk of machinery damage. Rolling is a necessity if there are a lot of rocks or corn root balls in the field, or if the soil surface is very uneven, posing a risk of substantial earth tag at harvest.
Timing
Rolling can be done immediately after planting to two days after planting, or post-emergence. Under dry, windy spring conditions, rolling after seeding poses a greater risk of soil erosion. Rolling immediately after planting can also be an issue if the soil is wet, causing soil sealing or crusting that can inhibit emergence. Under both of these conditions, post-emergent rolling is a better option.
If your goal is post-emergent rolling, target the V1 (first trifoliate) stage on a warm day or the warmest part of the day (~25°C). Avoid rolling in the morning when plant turgor pressure is high, which can cause plants to snap. Plants at the hypocotyl arch (hook) stage and V3 (third trifoliate) stage or later, are most susceptible to breakage. The V1 stage is a good indicator that plants have grown past the hook stage but have not yet reached third trifoliate. Soybean plants that are rolled at the VC (unifoliate) or V1 stages can bend and bounce back with much less damage. Don’t delay rolling too long after planting, as hypocotyl arches could be located just below the soil surface.
In comparison, the epicotyl is first to emerge for field peas. It is more pliable and less susceptible to breakage than the hypocotyl of bean plants. Field peas can be rolled safely until the 2nd to 3rd node stages. Dry beans behave similarly to soybeans and the same rolling precautions should be followed.
Advantages of Soybean Rolling
- Smoother and firmer seedbed
- Easier harvest
- Faster combine speeds
- Reduced risk of equipment damage
- Cleaner seed at harvest (reduced dockage from stones and soil)
Disadvantages of Soybean Rolling
- Risk of soil sealing or crusting
- Increased risk of wind or water erosion
- Tractor tire damage to emerged plants
- Increased risk of disease and lodging, if plant damage occurs
- No yield increase
Adapted from University of Minnesota Extension
Soybean Rolling Research
When is the best time to roll?
Research conducted by the University of Minnesota examined soybean rolling at different stages – pre-plant, post-plant, 50% emergence, V1 and V3, compared to no rolling. No significant differences in plant stand, average yield and seed quality were found between treatments. Soybeans in this study were safely rolled until the V3 stage. However, there is an elevated risk of breakage at V3 and it is not recommended to roll that late.
Do I need to roll non-stony land?
Two research projects on land rolling took place in Manitoba during 2018 and 2019. Both projects were funded by MPSG and were a collaborative effort with the On-Farm Network to test rolling on a full field scale. The first project was conducted by the Prairie Agricultural Machinery Institute (PAMI) looking at the economics of rolling non-stony land, including fuel consumption and header loss. The second project was conducted by Dr. David Lobb at the University of Manitoba examining the impact of rolling on soil erosion, plant growth and yield.
In 2018, field locations were near Dencross, Rosenfeld, Culross and Randolf. Only two of these sites had non-stony Red River Clays. In 2019, there were two sites near Brunkild and two sites near Starbuck. Rolled versus unrolled strips were compared within each field and both projects utilized the same fields.
Project 1 – Economics
The average cost of rolling based on the field trials completed during this project was $4.40/ac when an appropriately sized tractor is used. Most cooperating producers used an over-sized tractor because it was the only unit available to them or to address excess soil moisture concerns. In these situations, the cost of rolling was >$5/ac. However, a gear-up/throttle-down strategy can reduce the fuel consumption rate and resulting operating costs.
Header losses ranged from 1.4 to 3.9 bu/ac across all sites and treatments. In terms of protecting yield and minimizing loss at the header, unrolled plots outperformed rolled plots at two out of three sites. Extreme moisture conditions in the fall of 2019 prevented the completion of a full data set. A final conclusion regarding the impact of rolling (positive or negative) on header losses cannot be made at this time. Follow-up data collection has been proposed.
Operators did not have to alter harvest speed between treatments, nor did they notice any difference in handling of equipment or ride comfort. However, all participating producers felt the need to be more alert in the unrolled plots in case of a “rogue” stone that could cause damage to the combine. Producers should decide whether to continue rolling by weighing the cost of rolling (approximately $5/ac) against the potential risk of equipment damage.
Project 2 – Soil Erosion, Plant Growth and Yield
Sediment traps were placed in fields after rolling to capture any soil movement by wind. Soil and sediment accumulated within the traps, but did not differ significantly between rolled and unrolled areas. Considering that in most cases the unrolled strip was surrounded by rolled land across most of the field, it is possible that blowing sediment from the rolled area entered the trap within the unrolled area. The ability of the soil to blow will also depend on a field’s landscape, soil moisture in a given year, timing of major wind events and other management practices, such as residue management. Assess erosion risk from rolling on a field-by-field basis each year.
Of the other measurements taken, plant population (39 vs. 36 plants/m2), the number of pods per plant (33 vs. 27) and yield (36 bu/ac vs. 32 bu/ac) were greater, on average, in the unrolled strip compared to the rolled area of the field. No significant differences in plant height, lowest pod height and thousand seed weight were found between rolled and unrolled areas.