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Spring Residue Management Considerations

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(05/07/20)

Unharvested crops from last year, high amounts of crop residues covering the soil’s surface due to a wet fall that precluded tillage in areas where it is normally done, an abnormally cold April and this week’s rain and cold weather has seriously impeded normal planting progress (if not a perfect storm, I don’t want to experience one!).

Unharvested crops from last year, high amounts of crop residues covering the soil’s surface due to a wet fall that precluded tillage in areas where it is normally done, an abnormally cold April and this week’s rain and cold weather has seriously impeded normal planting progress (if not a perfect storm, I don’t want to experience one!). In the aforementioned list of challenges, the management of crop residues is basically the only factor you have some control over this spring as you try to get your crops planted in a timely manner. The following are some principles to consider as you decide how to most effectively manage excessive crop residues.

Crop Residues Impact Soil Drying – Crop residues slow soil drying. This is an obvious point and the reason that most farmers in the wetter regions of the state do some sort of fall tillage. Without fall tillage these soils may take too long to dry in the spring, frequently causing delays to spring field work. Dr. Aaron Daigh, soil physicist at NDSU, in one of his winter talks presented data that showed that 1 inch of residue reduces the relative evaporation rate from the soil to only 30% of that of a bare soil. Thicker residues reduce evaporation even further (this presentation can be reviewed at https://mnwheat.org/wp-content/uploads/2020/02/2020BestDaigh.pdf). This means that if a bare soil takes 3 days to dry after a rain to the point it can be worked, a soil with an inch of residue will likely take 9 days to get to the same condition. Furthermore, he reported that it is not residue type or weight, but depth of the residue on the soil that determined the rate of evaporation from the soil. Accordingly, erect residues will permit greater drying than those that has been chopped and spread.

Options for management excessive residues in the spring – Normally, crop residues are best managed in the fall through removal (baling), grazing or tillage. Managing residues in the spring are more challenging. Spring residue management options include doing nothing (planting directly into them), performing some type of tillage to cut and bury them or burning them. For no-tillers in western ND that have unharvested small grain crops, planting directly into last year’s crop may be the best option. Research elsewhere has shown there is limited yield drag when planting into standing wheat residues compared to more traditionally harvested fields. Obviously, planting wheat after unharvested wheat can be problematic due to the potential for massive amounts of volunteer wheat arising from the unharvested crop. In this scenario, I would recommend planting something other than a small grain so that you have some way to control the volunteers. When no-till planting corn or other warm season crops, use residue managers that are properly adjusted. Moving residues from directly above the seed row can improve emergence uniformity and may allow the soil to warm up faster directly over the seed.

Spring tillage for managing residues is a poor choice when soils are wet, even though burying the residues will help dry the soil. Tilling wet soils results in compaction, damages structure and creates poor seed beds. A good rule of thumb is, if it is too wet to plant it is too wet to till. One exception might be the use of vertical tillage to help blacken the soil if the residue cover is only 1 to 2 inches deep. Even though vertical tillage does not invert the soil and cover residues, it exposes enough soil (if residues are not too deep) to allow it to warm and dry more quickly than untilled soil. Tillage (disks and cultivators) can effectively manage residues once the soil has dried sufficiently. Unfortunately, this may be after the optimum period for planting the crop of interest, especially when the weather is cool and wet like this year for parts of the state. Use the near-term weather forecast to determine if “waiting and tilling” might be a viable option.

In some situations, burning may be the best option for managing residues this spring. This practice is not generally recommended as it results in nutrient losses, reduces the amount of carbon that is returned to the soil that is critical to biological processes and soil health, exposes the soil surface to erosion, impacts soil microbes and fauna near the soil surface and reduces soil structure. The long-term negative impacts of burning residues, however, may not be too significant if done only occasionally. The obvious short-term benefits are that much of the residue is immediately removed and the surface of the soil is blackened and dries more quickly. In some cases, it might be possible to plant these fields without prior tillage. Burning residues may also reduce some diseases and kill some weed seeds. Though a slow burn has the potential to kill some of the volunteer wheat seeds in fields that were not previously harvested, many seeds will survive and a fast burn will leave many viable seeds. Therefore, a strategy for dealing with volunteers during the season in these situations is needed. If you decide to burn, follow local regulations, and use best practices and care so that the fire doesn’t move beyond your own field.

Prevented Planting as an Option – If the crop is insured, another option for dealing with fields that are too wet to plant before the final planting date, is to take the prevented planting option. There may situations (i.e. a newly rented tract of land) where an unharvested field may not qualify for Prevent Plant so discuss this with your insurance agent well in advance of any decision. If taking Prevent Plant, consider management practices that will reduce the likelihood of Prevent Plant the following year, encourage soil health and control the buildup of weeds. More specifics on these topics in future articles.

Burning this corn field effectively removed surface

Joel Ransom

Extension Agronomist, Cereal Crops

 This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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