Land Rolling (05/26/22)
Land rolling is a common practice used in soybean and dry bean fields in North Dakota and northwest Minnesota. Land rolling can also be used for other pulse crops. The practice is used to manage rocks or corn root balls by pushing them into the soil, in order to improve harvesting efficiency and reduce combine damage. Rolling residue and flattening of stalks may cause the corn root balls to break apart quickly. The better residue contact with the soil may aid in the microbial decomposition of the residue, especially in a reduced tillage system. Other benefits of rolling include less down time and wear-and-tear on harvesting equipment, faster combine speeds, and reduced operator fatigue.
Rollers are pulled across the soil in the spring, if possible right before or after planting. The drums should exert a packing force of about 3 pounds per square inch. Land rolling could cause plant injury if done after the crop is emerged. There is a cost associated with rolling the field. A recent Canadian study estimated the average cost of rolling at $3.50 per acre with appropriate tractor size. With an oversized tractor, the cost would be closer to $4 per acre. These numbers were generated in 2019. With current higher fuel prices, the cost would be even higher than reported in the study.
The disadvantage of rolling is its effect on surface soil structure. Rolling pulverizes surface soil aggregates, which may cause the sealing of the soil surface. The even surface is more prone to wind erosion and, due to the reduced infiltration rate, there may be water movement over the surface and ponding in small depressions. Do not roll when the soil surface is moist to reduce the risk of crusting or sealing and soil sticking to the roller. Do not use rolling to level soil ruts.
During a three year University of Minnesota study with 7-site years, there were no significant differences in stand, average yield, or seed quality among the treatments. The treatments included rolling pre-plant, post-plant; 50% emerged, first soybean trifoliate (V1), third trifoliate (V3) and no rolling. The study also concluded that soybeans could be rolled up to the third trifoliate growth stage (V3), when soybean plants are about 4-6 inches tall. Rolling in wet conditions may make plants more susceptible to soil-borne diseases. Rolling after V3 is not recommended because of the increased potential to injure plants, resulting in reduced yield. If rolling after emergence, roll in the afternoon, during the heat of the day, when soybean plants are flexible. When rolling, the wheel tracks usually cause more plant damage to the plants than the rollers themselves. Control wheel damage by configuring tractor tires and roller width to minimize plant injury.
As there was not a yield increase with rolling, the main benefit is the easier harvest operation. While the harvest after rolling might be easier, it is difficult to assign an economic benefit to the harvest ease during the long work hours and potentially limited light conditions during the evening.
Reference: Rolling soybean in the Upper Midwest
Extension Agronomist Broadleaf Crops