Hang on to your chequebook for cropping decisions

Highest returns come from soil testing to determine fertility rates plus choosing crop-protection products based on past pest problems and frequent scouting

After two years of a three-year trial, results indicate that the highest wheat yields and protein come from applying the highest level of inputs. But if you’re interested in the highest profits, you might want to hang on to your chequebook.

The trial is led by Chris Holzapfel, research manager at the Indian Head Agricultural Research Foundation (IHARF) in Indian Head, Sask., and the goal is to evaluate both the agronomic responses and the economic returns of Canada western red spring wheat under several combinations of inputs.

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“We wanted to select treatments to demonstrate the contributions of individual crop inputs when either added to a low-input system or removed from a high-input system,” Holzapfel explains. “The scope was narrowed to include combinations of seed treatments, higher seeding rates, enhanced fertility, plant growth regulator and foliar fungicide applications. Although it would have been ideal to do so, it simply wasn’t feasible to try to evaluate every possible combination of inputs.”

The inputs

  • Seed treatments. Only fungicide was chosen because no specific insect issues were foreseen. Holzapfel says replicated studies showing yield benefits to seed-applied fungicides are limited in CWRS, but because of their potential benefits in stressful environments and because wheat tends to be one of the earliest-seeded crops in Saskatchewan, their use is common.
  • Seeding rate. The standard recommendation for spring wheat is 215-270 plants per square metre, but Holzapfel says that in environments where drought is reasonably unlikely and disease pressure is moderately high, some growers are targeting populations exceeding 300 plants per square metre. This reduces the infection window for fusarium head blight and makes foliar fungicide applications easier to time. However, increased seeding rates can increase the risk of lodging in some varieties and if there’s a drought, higher plant populations can speed maturity and may even reduce yield.
  • Fertility. Spring wheat has an estimated total uptake of 1.9-2.3 lbs. N/bu., 0.73-0.88 lb. P2O5/bu., 1.63-2.00 lbs. K2O/bu. and 0.2 lb. S/bu. “While K and S are less likely to be limiting throughout most of Sask­atchewan, soils low in N and P are common,” says Holzapfel. “Nitrogen is also the most or among the most important management factors affecting grain protein concentrations, an important quality parameter for CWRS wheat.”
  • Plant growth regulators. Chlormequat chloride (Manipulator) was available for the 2018 growing season and has performed well in numerous private and public trials dating back to 2013, so was included in the trial. Past work suggests that PGRs are most likely to be beneficial under intensive management where yield potential and risk of lodging are higher.
  • Foliar fungicide. Another input in the study was foliar fungicide to treat FHB. Holzapfel notes that even when FHB is not a yield-limiting factor, fungicides used to control it are also effective against leaf spot diseases. Consequently, particularly when a fungicide is not applied at the flag-leaf stage, much of the yield response can be attributed to reduced leaf disease. However, to prevent potentially confounding effects of this in the study, no fungicide was applied at the flag leaf stage.

Conditions in 2018 and 2019

In 2018, the first year of the study, there was dry weather and somewhat below-average yield potential at Indian Head.

Some of the study plots received intensive input levels and others low, but the low-input wheat was still reasonably well-managed (midge-tolerant variety/certified seed, timely seeding and weed removal, modest but balanced fertility).

“With regard to economic returns, the assumptions used were crude but clearly showed the intensively managed wheat to be the least-profitable treatment and considerably less profitable than the low-input system on the opposite end of the spectrum,” Holzapfel says. “The PGR and, to a lesser extent, foliar fungicide were the only inputs to increase profits over the low-input treatment. However, this does not take into account any quality considerations like protein.”

Input effects on marginal profits Indian Head 2018 ($/ha). (z- Not adjusted for differences in seeding rate between Trt. 2 and 7; y- Assumes certified seed price of $0.478/kg; x- Assumes $725/tonne for MAP and $525/tonne for urea.)

Holzapfel notes that results may vary dramatically with local conditions, but 2018 results suggest that wheat producers must choose their inputs carefully to stay as profitable as possible. He says that due to the limited number of treatments, it’s hard to determine what the optimal combination of inputs may have been in 2018. But in general, he recommends two actions for the best chance to achieve near-optimal yields and quality while managing costs and maximizing returns. These are soil testing to determine fertility rates and choosing crop-protection products carefully, basing decisions on past pest problems along with thorough and frequent crop scouting.

Growing conditions were also somewhat below average in 2019, but economic results were similar.

“For the second year, the project results clearly showed the intensively managed treatments to be least profitable under the conditions encountered, considerably less so than the most profitable low-input system,” Holzapfel says.

“These responses, keeping in mind that environmental conditions vary for everyone, were not necessarily unexpected given that there was relatively low yield potential, lodging and disease pressure combined with moderately high residual nutrient levels.”

Input effects on marginal profits Indian Head 2019 ($/ha).

Again, the results demonstrate that soil testing to determine fertility requirements and choosing crop-protection products based on knowledge of past pest problems combined with frequent crop scouting is the best strategy.

Holzapfel notes all inputs have their place, but says he is confident in the conclusions from the two years of data.

“Throwing everything at it to grow the biggest possible crop won’t generally make you the most money. We shall see what results come from the same trials this year.”

The project is supported by the Agricultural Demonstration of Practices and Technologies (ADOPT) initiative under the Canadian Agricultural Partnership bilateral agreement between the federal government and the Saskatchewan Ministry of Agriculture, with support from Agriculture & Agri-Food Canada. Crop protection products are provided by Corteva Agriscience, Belchim Canada and Bayer.

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