Ontario Field Crop Report – July 27, 2022

Straw bales post-wheat harvest

Weather Conditions

The percentage of average precipitation during the current growing season is quite variable across the province. Crop conditions generally mirror precipitation levels with below average precipitation received in mid-western and southern Ontario causing significant crop stress, especially on lighter textured soils. Conversely, parts of eastern Ontario are above average with generally good crop conditions.

Figure 1. Percent of average precipitation (mm) from April 1 to July 25.

Wheat Harvest

Significant progress has been made on winter wheat harvest. Yields between 90-110 bu/acre have been common, but have ranged from the low 70’s on sandy soil to the low 140’s. In general, the 2022 winter wheat crop has been of good quality and yield.

Nutrient removal from baling straw

There is always a debate over whether straw should be sold, based on its value for soil organic matter. Long term rotation research at the Elora Research Station has clearly demonstrated that the value of cereals in the rotation, even with straw removed, far outweighs any negative impact of straw removal. Even with straw removed and no cover crop (red clover), yields of subsequent corn and soybean crops increased dramatically (corn 12%, soybeans 14%), and soil health parameters, such as organic matter and water stable aggregates, are improved considerably. If selling the straw improves the profitability of cereal production to the point that producers keep cereals in the rotation more frequently, then the producer should sell the straw.

Table 1 provides an overview of phosphorus and potassium levels removed from 1 ton of straw and the corresponding estimates of fertilizer costs to replace those nutrients.

NutrientAvg. to Max. Removal
(lbs actual/ton)
FertilizerFertilizer Replacement (lbs/ac)Fertilizer Cost
Phosphorus3.2 – 6.0MAP
6.5 – 11.50.60$3.90 – 6.90
Potassium16.8 – 42.5Potash
28 – 70.80.50$14.00 – 35.40
Total value ($/acre):$17.90 – 42.30
Total value (¢/lb of straw):¢ 0.8 – 1.92
*A MAP value of $1320/metric tonne, and a potash value of $1080/metric tonne were used in these calculations.

Table 1. The average to maximum amount of phosphorus and potassium removed from harvesting 2200 lbs (1 ton) of winter wheat straw per acre, along with estimated fertilizer replacement costs* presented on a per acre and per pound of straw basis.

Post wheat harvest weed management strategies

The established of cover crops after cereal harvest has been shown to reduce weed seed production and dispersal to the soil. This would be of particular benefit when trying to manage glyphosate resistant weed species like Canada fleabane and waterhemp. Some highlights from recent studies include:

  • Fall planted cereal rye on sandy soils reduced glyphosate resistant Canada fleabane biomass by as much as 96% in one University of Guelph study.
  • A second University of Guelph study that evaluated cover crops planted in the fall on heavier soil textures revealed that glyphosate resistant Canada fleabane biomass the following season was reduced by 36% with oilseed radish, 41% with oats, 52% with crimson clover and 57% with cereal rye.
  • A University of Missouri study demonstrated that fall planted cereal rye reduced early season summer annual weed emergence (including waterhemp) by 41% the following season.
  • A University of Arkansas study observed up to a 69% reduction in Palmer amaranth seed production where a cereal rye cover crop had been planted.

If you’ve never planted a cover crop after winter wheat harvest, oats is a good one to start with. Its relatively inexpensive, easy to establish, does not over winter and could be used for extra forage feed if the opportunity exists.

Managing weeds in red clover following cereal harvest

If red clover was under-seeded into the wheat crop there are a couple of ways that you can knock back annual weed growth so that you can let the red clover grow as much as possible and maximize its nitrogen credit. The tried-and-true method, but most labour intensive, is to “clip” or trim the top of the red clover which will ‘chop off’ the weed seed heads at the same time. OMAFRA and the University of Guelph have experimented with applications of MCPA to manage broadleaf weeds in a red clover cover crop. There are three key learnings from this work:

  1. The ester formulation of MCPA causes significantly less plant damage then the amine formulation.
  2. Red clover biomass is initially stunted during the first week after application but does recover within 2-3 weeks.
  3. Targeting broadleaf weeds when they are smaller will result in better control, if annual grassy weeds are predominant then the application of MCPA Ester will be insufficient and clipping is a better option to minimize weed seed dispersal.

Weather Data – July 18 – 24, 2022

LocationYearHighest Temp (°C)Lowest Temp (°C)Rain (mm)Rain (mm) April 1stGDD 0C April 1stGDD 5C April 1stCHU May 1st
10 YR Avg. (2011-20)29.216.511.6351185012781976
10 YR Avg. (2011-20)29.014.516.8300173911711841
10 YR Avg. (2011-20)29.215.317.7324171511521819
10 YR Avg. (2011-20)28.715.816.3308172211571828
10 YR Avg. (2011-20)27.813.29.931715419901621
Mount Forest202230.617.523.423014759781508
10 YR Avg. (2011-20)
10 YR Avg. (2011-20)28.612.79.8279156210111625
10 YR Avg. (2011-20)29.013.317.9314163810881728
10 YR Avg. (2011-20)26.710.319.127012968291415
10 YR Avg. (2011-20)27.312.617.729813939031516
Thunder Bay202232.412.911.437511136721135
10 YR Avg. (2011-20)26.311.013.729512137341279
Fort Frances202228.514.112.048711967571287
10 YR Avg. (2011-20)27.311.112.628713408431439
Report compiled by OMAFRA using Environment Canada data. Data quality is verified but accuracy is not guaranteed. Report supplied for general information purposes only. An expanded report is available at www.fieldcropnews.com.

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