Revising the crop nutrient uptake and removal guidelines for Western Canada

Agronomy
Written By SaskCanola

Term: 3 years ending March 2023
Status: Complete
Researcher: Fran Walley, Richard Farrell, Gazali Issah, U of S; John Heard, Manitoba Agriculture; Lyle Cowell, Nutrien Ag Solutions
SaskCanola Investment: $22,009
Total Project Cost: $151,728
Funding Partners: Alberta Wheat Commission, Prairie Oat Growers Association, SaskFlax, SaskWheat, WGRF

Grower Benefits

  • Regular soil testing is an important tool for assessing current soil nutrient status and determining appropriate application rates to achieve yield goals.

  • Nutrient uptake and removal estimates are an additional tool to help maintain or build soil fertility levels.

  • The revised nutrient uptake and removal chart was developed specifically for crops grown in Western Canada. Importantly, the data demonstrates considerable variability around the mean due, in part, to known differences in weather and management, and thus these estimates are to be used as guidelines and should not be viewed as prescriptive.

  • There are differences in observed grain nutrient concentrations from the last survey and the new survey for some crops and nutrients. This suggests that management practices and new varieties have resulted in improved nutrient use efficiency on a per bushel basis, although higher yields remove more nutrients on a per acre basis.

  • Although survey data indicates lower sulphur (S) removal by canola and flax seed than previous estimates, given the importance of S to canola production and the variability in the estimated removal, it’s important to opt for a higher estimate of S removal than suggested to avoid potential S deficiencies.

  • An on-line calculator has been developed (https://prairienutrientcalculator.info/). The calculator uses the 75th percentile of the survey data as the nutrient coefficient, with the goal of limiting the risk of underestimating nutrient removal. The 75th percentile represents that point at which 75% of the survey values were below the coefficient value and 25% of the values were above the coefficient value.

Project Summary

The nutrient uptake and removal guidelines for crops in Western Canada were last revised in 2001 by the Canadian Fertilizer Institute (CFI). This project aimed to develop new nutrient uptake and removal guidelines for 14 annual crops grown in Western Canada, based on measurements taken from straw and seed samples. The new measured estimates were also compared to published and unpublished literature from Western Canada. The new guidelines include removal and uptake estimates for macronutrients (N, P2O5, K2O, S) and micronutrients (Cu, Zn, B). The study was conducted from 2020-2022, with biomass collection occurring in 2021 and 2022 only because of COVID-19 restrictions in 2020. Limited samples for both seed and biomass were collected in 2021 because of the prairie-wide drought. However, this gave researchers the opportunity to assess how nutrient uptake and removal were affected by drought. By comparing grain samples collected in 2021 with those collected in 2020 and 2022 it was determined that although drought impacted crop yields, the removal and uptake (on a pounds per bushel basis) remained relatively unaffected by drought conditions beyond the variability that was associated with “normal” years.

The 14 crops studied included barley, corn, durum, oats, spring wheat, winter wheat, canola, flax, soybean, mustard, chickpea, dry bean, lentil, and field pea. Faba bean was added because samples were available and seeded acres had increased. The original goal was to collect 100 grain/seed samples of each of the 14 crops in each of the two years, with the actual number of samples collected in each province reflecting the seeded acres. In response to the 2021 drought, the biomass sample collection was reduced to 20% of what had been planned, leaving the remaining 80% of samples to be collected in 2022 (Table 1). Both grain and biomass samples were analyzed for nutrient content. Moisture content was also adjusted to the recommended threshold set by the Canadian Grain Commission.

Table 1. Number of biomass and seed/grain samples collected during the project.

The purpose of these estimates is not to replace soil testing, but to assist in developing fertilizer management plans, or to help interpret soil test reports. These estimates should always be used in conjunction with soil testing. Total nutrient uptake and removal levels are dependent on crop yield and can be affected by variety, soil fertility and growing conditions. Table 2 shows the new nutrient uptake and removal chart. The mean values represent the average removal and do not account for the variability that exists within a field. The nutrient removal calculator has the base nutrient coefficients set at the 75th percentile (and not the mean) (Table 3). This means the calculator is more likely to overestimate crop nutrient removal rather than to underestimate it.

Table 2: Average (mean) grain yield (bushels per acre) and nutrient removal (in grain) (lbs per bushel of grain produced ± standard deviation) across Western Canadian prairies in 2020, 2021, and 2022 growing seasons. Bolded values are the average grain yields and nutrient removal, and numbers in parenthesis reflect possible range.   

Table 3: Grain yield (bushels per acre) and 75th quantile values for nutrient removal (in grain) (lbs per bushel of grain produced) across Western Canadian prairies (2020-2022). The 75th percentile values were used as the nutrient coefficients in the removal calculators.

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