When excessive heat strikes, the best agronomic management is critical today and for the long-term

Western Canadian farmers experienced a seemingly never-ending heat wave at this summer’s onset, and the destructive pressure of drought looms large. With concerns for yields, soil fertility imbalances, crop health and quality, staying on top of good agronomy has been critical.

When drought strikes, it’s effects reach beyond the current year’s yields. From plant quality to end-use, to next year’s crop planning, and nutrient management for years to come, dry conditions can have lasting impacts. Because nutrients move through the plant’s moisture uptake, drought and soil heat impair nutrient uptake and nutrient use. These effects vary from crop to crop.

Get to know your soil

Following a drought year, nutrient levels left in the soil will likely be higher and may mean less inputs required next year. Soil testing allows growers to understand the nutrient levels while avoiding over-fertilizing, unnecessary spending, and environmental impacts.

Garth Donald, Decisive Farming’s manager of agronomy and co-founder, explains. “If you fertilized expecting a 60-bushel wheat crop and in today’s conditions it’s likely to be a 20-bushel crop, it will only take up what it can use,” he says. “In dry conditions, the need for nitrogen promotes higher protein levels that could sit as high as 16 to 18 per cent.”

High protein can change end use, with drought-affected crops being cut and baled for feed, drastically reducing the price received for that crop. “There will probably be some malt barley crops where the excess nitrogen has driven protein levels up as well,” says Andrea Bilodeau, Decisive Farming’s senior agrologist. “When it’s driven too high, that malt won’t pass muster for malting contracts, and it may be sold into the feed market.”

Canola fertilized for an expected 50-bushel yield that produced only 20-bushels won’t use as much fertilizer, and growers can expect to see much of their fertilizer go into reserve for next year. Understanding where those levels end up will be essential to making sound decisions for next year.

This includes leveraging variable rate (VR) technologies and soil sampling to understand where a crop performed well compared to where it struggled. “Soil testing allows us to understand what that crop nutrition is in those situations at the zonal basis,” says Donald.

Soil samples should be taken throughout the year and tracked for use in future drought years. Based on the results, growers can make more informed decisions around application rate changes for each nutrient as each will respond differently to drought conditions. For example, “In the case of extremes, potassium is essential for the plant to control its ability to open and close its cuticle during key times,” Bilodeau.

What is left in your fields can make the difference

Producers can achieve better yields by planning and building optimal nutrient levels, as was the case last year for a Decisive Farming client. “We did attribute some of his increased yields to a strong fertility program and a cognizant look at what needed to be put down in the field,” says Bilodeau. “We don’t just think in terms of this year but which nutrients we can build over time, especially with potassium and phosphorous. In some years, that can certainly provide some insurance.”

Another way to manage different fertility levels and rebalance the soil’s health lies in adjusting the crop rotation. “One of our customers was expecting this dry weather and we talked about that,” says Bilodeau. “He was very selective and opted to use more drought resilient crops.”

When rebalancing for next year, soil samples will reveal where changes are required. “If a field carries over high residual nitrogen levels going into 2022, it’s probably not a good idea to put a pulse into that field,” says Donald. “They are not going to perform and it’s a waste of the nitrogen. It may be more suitable to plant another crop that can use it. That’s the value in looking at a VR program – to be able to have that data set of soil data information broken out into five-to-six sample point areas rather than just one with that data set to make these decisions.”

Planning for the future

Having and saving that soil sampling information can pay off next time drought hits, showing which varieties performed best under those conditions. “Maybe we’re looking at similar weather next year or four years down the road. What performed this year and what didn’t? How do you make that decision without that data set?” Donald asks. “Your data needs to be in a usable form, in one platform, that’s accessible.”

Fertility planning and adjustments often happen at least a year ahead of time. Communication with a trusted agronomist should be ongoing to get the best results. “We’re having these conversations right now for next year,” says Bilodeau. “We’re using that information from our soil probes, our agronomic knowledge, looking at the crops and digging holes in the fields. We’re talking and planning for next year right now.”

These conversations will create nutrient plans that meet the goals of 4R nutrient stewardship: applying at the right rate, with the right source, in the right place, and at the right time.

“We continue to meet the 4R expectations,” says Bilodeau. “We don’t fertilize to excess. Where some might put 100lbs of nitrogen right across the field, we use that as an average, with low areas in the 40-50lb range. We’ve met the right place in the right amount. Growers who were going to apply top-dressing options have pulled back at the right time because the potential is not there. We’ll be balancing out each nutrient source, including nitrogen, potassium and phosphorous in all we do.”