Calculator provides another tool for making soil fertility management decisions.
August 30, 2023 By Donna Fleury
A new online calculator for crop nutrient removal was recently made available in Western Canada. Used together with regular soil testing, the calculator provides another piece of information for growers to use when planning and making soil fertility management decisions.
“Although there are other crop nutrient uptake and removal calculators available, the data behind this new online calculator was recently collected from commercial fields in Western Canada,” explains Fran Walley, professor emerita in the department of soil science at the University of Saskatchewan (USask). “We wanted to make sure the data was from the Prairies and based on current cropping systems and commercial farm production. We have long relied on a valuable tool for crop nutrient uptake and removal produced by the Canadian Fertilizer Institute, with the last update released in 2001. There have been significant changes in cropping systems in Western Canada since that time, with the move to conservation and no-till, the addition of pulses and other new crops into rotations, new and improved variety development and different management systems. Therefore, our question was whether or not those guidelines were still reflecting the nutrient uptake and removal by our current crops and to determine if the new data collected still matches or needs to be updated.”
Originally initiated in 2020 with USask research collaborator Richard Farrell, the goal of the project was to determine and revise estimates of the nutrient uptake and removal of crops commonly grown in Western Canada. Factors such as COVID-19 in 2020 and the significant drought conditions in 2021 extended data collection over three years to 2022. More than 2,200 grain seed and biomass samples representing 14 different crops were collected from commercial fields at harvest across Alberta, Saskatchewan and Manitoba during the project.
Walley emphasizes how the sample collection couldn’t have happened without the support and willingness of growers to provide access to their fields and the many agronomist collaborators collecting samples. Agronomists with Nutrient Ag Solutions in Alberta and Saskatchewan, field staff with Manitoba and Saskatchewan provincial agriculture departments and researchers at Saskatchewan Agri-ARM sites all provided support in collecting samples throughout the project.
“The new online calculator is based on this recently collected, locally pooled data from crop varieties being grown across the Prairies,” says Walley. “The data helps to calculate the total amount of nutrients removed from the soil by the harvested crop and exported from the field in the grain. It provides more recent information that can help growers tweak their fertilizer and soil management decisions on the farm. However, the results are not prescriptive because there is always variability in the data and a range for the results. Research has shown that nutrient concentrations in the harvested seed or grain varies from year to year and with crop variety, soil fertility and climatic conditions. Therefore, the calculator provides another piece of information indicating that on average, this is the nutrient removal of what a specific crop with this yield would be removing. It does not predict or guarantee what will come off a field, but it can give you an estimate, for example, of what is going to be removed by a 45 bu/acre canola crop.”
Walley adds it is also important to remember that fertilizer use efficiency is not 100 per cent. Crops are not able to extract all available plant nutrients from the soil, as some of it can be lost or tied up and retained in the soil in microbial biomass. Therefore, for any given yield, the total nutrient supply in the soil (soil plus added fertilizer) should be somewhat greater than the amount removed by the crop to maintain soil nutrient levels.
The calculator can also be useful for planning longer term strategic soil fertility practices for maintaining or building nutrient levels in the soil, such as for phosphorus. Along with the macronutrients nitrogen, phosphorus, potassium and sulphur, the micronutrients boron, copper and zinc were also included in the calculator. This is not to suggest that micronutrient deficiency is a big problem right now, however, recognizing the high yielding crops being grown, it is probably a good idea to keep track of the micronutrient status.
“The free online calculator is easy to access and use,” says Walley. “Users can go into the calculator, select their crop type and specific crop, then enter a yield estimate. The calculator will then provide a nutrient removal estimate in lb/acre for each nutrient for that crop. The calculator provides a specific piece of information that only helps tell part of the story, but it is also a cool part of the story. This additional information, when taken together with a good quality soil test, can help growers assess and make nutrient adjustment decisions as part of an overall soil fertility and fertilizer management strategy.”
The online calculator is available at prairienutrientcalculator.info.
Funding for this project was provided by the Western Grains Research Foundation, Alberta Wheat Commission, Prairie Oat Growers Association, Saskatchewan Canola Development Commission, Saskatchewan Flax Development Commission, Saskatchewan Wheat Development Commission, with logistical support provided by Nutrien Ag Solutions and Manitoba Agriculture and Resource Development.