Post-Harvest Field Cleanup

Friday, October 25, 2024

Reflect on this year’s results to make next year’s crop better.

By Emily Mckinlay

The end of harvest often feels like a finish line for the growing season. As crops come off and the busy season ends, it is an opportunity for grain and oilseed farmers to look ahead and set up their fields for success in 2025.

Carmen Prang, agronomy extension specialist at the Saskatchewan Wheat Development Commission, suggests that producers review the decisions they made for the 2024 growing season while the results remain fresh.

“We have put in a ton of work to finish the current crop year, but there are always more decisions that can be made to set up your farm for the next year,” says Prang.

“We can take time to evaluate our decisions from the last year, like weed, insect, and nutrient management, and we can begin addressing our plans for the next year.”

Dr. Breanne Tidemann, a research scientist with a focus on weeds at Agriculture and Agri-Food Canada, adds, “After harvest is a good opportunity to look back at the outcome of the management decisions for that year and decide how you want to manage things differently next year.”

What steps should producers take to clean up their fields post-harvest as they reflect on the current year?

Managing residue

There are several options for managing straw and residue after harvest. The handling of residue can affect weed control, soil moisture, and soil nutrients in the subsequent year’s crop. Each farm will have its own goals and needs, which will be a factor in this decision.

Prang notes that 1.66 lbs of residue is typically created for every 1 lb of grain harvested. She says producers can manage their straw well before harvest in several ways.

“There are some things farmers might want to consider before they even think about harvest,” says Prang.

“Are you selecting a variety that will have lots of straw? If it’s looking like a heavy crop, you can consider a plant growth regulator (PGR), which will shorten the straw and create less residue.”

At the time of harvest, if baled straw is not needed for livestock, chopping the straw out of the combine is another alternative.

“Most combines have straw choppers, but there are after-market options as well,” says Prang.

“This cuts residue into smaller pieces and evenly distributes it behind the combine, so that you don’t have to rely on other methods as much. The key here is the even distribution of that material.”

Baling, swath grazing, harrowing, tillage, and burning straw are all options used in the Prairies for removing or incorporating residue. When reviewing these options, it is important to consider the nutrients that will be removed from the field by baling, grazing or burning residue.

“Straw has organic matter potential,” says Prang.

“As it breaks down, it eventually becomes organic matter, which plays a role in soil moisture and water holding ability and is important for soil structure, which affects compaction and erosion. Straw contains nutrients as well, so producers should consider that nutrient value of the straw they may be removing and look at fertilizer value.”

When incorporating residue through tillage, Prang says that this year’s management can have a significant impact on the following year’s crop.

“If we are leaving residue, make it smaller so it’s easier and faster to break down. It should be properly distributed as well, so that there are no areas with heavy residue,” explains Prang.

“And you have to keep in mind that straw-bound nutrients will go back into the soil as it breaks down, but it will not all be available for next year’s crop. It takes a while, so it not only impacts next year’s crop, but the years following as well.”

Tillage has benefits but can also create challenges. It can increase soil-to-straw contact to increase the rate of break down, and it can help dry and warm up the soil faster in the spring. Conversely, it can increase soil erosion and damage soil aggregates. If the farm is in a dry region, tillage can release valuable soil moisture.

Each farm has unique characteristics which will influence how they clean up residue and get their fields ready for the fall.

Cleaning up weeds

During and after harvest is also a good time to review wins and misses with weed control for the current crop year. In the fall, perennial and winter annual weeds begin to emerge and should be managed before they cause problems in the next crop.

Tidemann says that dealing with these weeds might not be as effective in the spring.

“Winter annuals are the first that come to mind. These are weeds that emerge in the fall, survive the winter and continue growing in the spring,” says Tidemann.

“The problem is that by your pre-seeding burn-off, some of those weeds will be out of the stage of control because they’ve been growing since fall.”

These winter annual weeds include cleavers, shepherd’s purse, and stinkweed.

Prang adds, “Winter annuals are strong competitors for water and nutrients in the spring. These weeds have a head start. You want to make sure you’re controlling them from the end of harvest to freeze-up, weather dependent.”

For perennials, Canada thistle, quackgrass, and perennial sow-thistle are just a few of the weeds that producers should be watching for. Prang says that fall is also an ideal time to control perennial weeds.

“If we have a really nice, long fall it will be crucial to manage these weeds. Usually, they are best controlled from mid-September to mid-October and you need the weeds to be growing after harvest to get control,” explains Prang.

Tidemann adds that this is because the plant’s energy sink will move as it prepares for winter.

“A lot of systemic herbicides will move from source to sink. That means they will move from where they are applied to where the sink is in that part of their cycle. If they are growing it will move to the stem; if they are flowering it will go to the flower,” says Tidemann.

“In the fall, most plants start to put their resources to the roots to be able to regrow from the root system the next spring.

“So, to get control of the plant and not just the top growth, applying in the fall to get into the root system will be more effective.”

During and after harvest is also an ideal time to identify which weed species are present in the fields, as well as any challenges with the current year’s weed control.

As producers combine, they have a chance to see the whole field from above. They can evaluate how the crops yielded, and see problem patches and spray escapes as they drive. They can also determine if there are specific species which appear to be escaping control. These would be candidates for herbicide resistance testing.

“Scouting is a big part of it. The best way is to have boots on the ground, seeing how many weeds are in the field and what kinds there are,” says Tidemann.

“Weeds in environmental stress conditions can change colour. Some of those weeds will go almost purple in colour, so you won’t see the field green up and might not notice the weeds from a drive-by or an image.”

Prang also encourages producers to keep their crop rotation in mind and consult their agronomist when selecting control options.

Gathering information

With the fields clean of residue and weeds, grain growers can take time post-harvest to reflect on the current year and start making decisions for the next year.

“It is a good time to reflect on the decisions you made and review how that turned out at harvest,” says Tidemann.

Prang recommends reviewing weed, insect, and nutrient management outcomes. The easiest place to start is soil sampling.

“You can plan which fields you want to do, or look at the whole farm. To reach yield and quality goals, it’s important to learn which nutrients are adequate, deficient, or marginal,” says Prang.

“In the fall, there is more time than in the spring to get a sample, go to an agronomist, come up with a plan, and order products.”

Prang also explains that in the fall, insects like sawfly and midge are overwintering, but it is a good time to review damage and control options for the following year. Producers should look for cut stems that are not the result of wind or rain. This could indicate sawfly damage.

The Prairie Pest Monitoring Network has resources to identify damage from sawfly.

Producers should also discuss the year’s crop stand, diseases challenges, and what comes next for their crop rotation.

Tidemann says, “Look at the story that the field tells you about the past year or two and what it means for the next chapter in that field’s story.” BF