The University of Saskatchewan has collected new data to revise outdated guidelines when it comes to fertilizing crops.
Using online calculators, farmers can calculate a crop’s nutrient removal, the level of each nutrient exported from the field, which can impact how they use fertilizer.
“The idea behind the calculator is farmers and agronomists can calculate what the crop that they have grown or plan to grow is likely to remove in the seed,” said Fran Walley, associate dean (academic) and professor in the College of Agriculture and Bioresources. “When a farmer harvests the seed and they are exporting from the field, not just the seed but all the nutrients that are in the seed, that is the information that the calculator provides.”
Farmers can work through soil reports and make nutrient adjustments as part of overall fertilizer management.
“If you have so many bushels of barley for instance, what would be the likely removal, a good estimate, of the amount of nutrients that are being removed,” Walley explained. “It should be used in conjunction with regular soil testing; so sometimes understanding what your soil test is showing you, you can really be helped out by knowing the crop I grew last year with so many bushels were removed, now the soil test is starting to make sense.”
Walley added the calculator does not replace a soil test but adds to understanding.
“Developing those fertilizer management strategies takes a little detective work and this is another tool that a farmer or agronomist can use.”
While the calculator is not a new tool, the most recent nutrient removal guidelines available are from 2001. In the past two decades, different crops, genetics, and rotations have been developed, outdating older farming practices.
“There are differences in soil, differences in management practices, and also is reflecting the crops that we are growing and the variety that are currently growing as well,” Walley said. “The calculator from the eighties was used from research plots and this calculator is based on seeds collected from commercial fields.”
The team collected on-farm samples from Alberta, Manitoba and Saskatchewan from 2020, 2021 and 2022, making the calculator specific to western Canada.
The calculator looks at macronutrients, nitrogen, phosphorus, potassium and sulfur.
“What’s new information is micronutrients, so we were also looking at copper, zinc and boron removal,” said Walley.
“It’s a good guide, but it’s not prescriptive,” Walley said, noting there is a lot of variability associated with the removal values.
Rich Farrell, research chairholder for Saskatchewan’s Ministry of Agriculture said that while the crops might be taking up a little bit less nutrients than in past years, the yields are higher.
“You are removing more nutrients from the field. So, it is really important to be looking at what you are taking off and what is in the soil which is why this is such a good complement of soil testing.”
The calculator is now available for the 2023 season at prairienutrientcalculator.info.