Ontario & Alberta crop nutrient planner
CropGPT turns your soil test into a fertilizer plan. Enter your crop, a realistic yield goal and your Olsen phosphorus and potassium values, and it returns nitrogen, phosphate and potash rates drawn from the OMAFRA Agronomy Guide for Field Crops (Publication 811) sufficiency tables — the same tables Ontario agronomists work from. It covers grain corn, soybeans, winter wheat, spring wheat, barley, oats and canola.
Every rate shows its own arithmetic. You can see the base nitrogen for your soil texture, the yield component, the credit deducted for last year's crop, and the soil-test band each phosphate and potash rate came from. Nothing is hidden behind a black box, which matters whether you are checking your own numbers or defending a recommendation to a client.
Manure, compost and biological inputs are treated as real fertilizer, not an afterthought. Choose the organic pathway and the tool sizes the tonnage needed and shows delivered versus required for every nutrient. Choose the synthetic pathway and it solves phosphate first, credits the nitrogen carried in MAP or DAP, then sizes the remaining nitrogen and potash so you do not pay twice for the same nutrient.
Alberta does not work the way Ontario does, and this tool follows that difference rather than papering over it. There is no provincial sufficiency table. Alberta sizes nitrogen economically: the right rate is the one where the next increment of fertilizer still pays for itself at your prices. Enter your soil-test nitrate, your expected crop price and your nitrogen cost, and the calculator adds nitrogen in 10 lb steps for as long as each step clears your target return — then shows you exactly which increment stopped paying, and why.
Yield response comes from Alberta Agriculture's published irrigated response tables (Fertilizer Requirements of Irrigated Grain and Oilseed Crops, Agdex 100/541-1) covering eleven crops: hard red spring wheat, soft white spring wheat, CPS wheat, durum, feed barley, malt barley, barley silage, triticale, triticale silage, canola and flax.
Alberta's nitrogen recommendation runs on soil-test nitrate-nitrogen (NO₃-N) sampled to 24 inches (0–60 cm) — considerably deeper than Ontario's 6 inch phosphorus and potassium sample, because nitrate moves down the profile and a shallow sample misses most of it. Alberta guidance is to split each core into 0–6, 6–12 and 12–24 inch depths (0–15, 15–30 and 30–60 cm).
For phosphorus, the Modified Kelowna extraction is the recommended test in Alberta. Alberta Agriculture states plainly that tests such as Bray or Miller & Axley are not effective at predicting crop response on these soils. This is a genuine difference from Ontario, which calibrates its phosphorus guidelines to the Olsen (sodium bicarbonate) test — the two are not interchangeable, and a number from one cannot simply be read against the other's tables.
Alberta's agricultural land spans several soil zones — Brown, Dark Brown, Black, Dark Gray, Gray Wooded, the Peace Region and Solonetzic soils — that differ sharply in moisture, organic matter and yield potential. Alberta publishes separate cost and return benchmarks for the Brown, Dark Brown, Black and Grey Wooded zones for exactly this reason. Nitrogen rates on Solonetzic soils are generally reduced to 70–80 per cent of the rate used on comparable normal soils, because restricted rooting makes response more variable.
Alberta has never published dryland nitrogen response curves. They exist, but only inside the province's own AFFIRM software (Alberta Farm Fertilizer Information and Recommendation Manager). Rather than invent numbers or quietly reuse irrigated curves on dryland fields — which would give wrong answers on most of Alberta's acres — the dryland path says so plainly and sends you to AFFIRM. If Alberta publishes that data, it will be added here.
Too much nitrogen placed in the seed row delays or destroys emergence, and the safe limit depends on seedbed utilisation, row spacing, opener width and soil texture. Alberta publishes maximum safe seed-placed rates separately for cereals and for canola and flax, which are considerably more sensitive. This is a real Alberta-specific safety calculation with no Ontario equivalent.
It is a single page with no sign-up, no account and no tracking of your field data — everything is calculated in your browser. Once loaded it keeps working without a signal, so it is usable in a cab or at a field edge. Farmer mode asks plain questions with picture guides; agrologist mode exposes soil-test categories, response ratings and editable rates for Certified Crop Advisers.
No. Ontario reads a rate off a soil-test band; Alberta picks the rate that still pays. That is why the Alberta calculator asks for your crop price and nitrogen cost — without them there is no way to say where the economics stop. It is the same logic the province's own AFFIRM software uses.
It is how many dollars of extra crop you want back for every dollar spent on nitrogen. At a 2:1 target, a 10 lb increment of nitrogen is applied only while the extra yield it buys is worth at least twice what the nitrogen costs. Raise the target and the rate falls; lower it and the rate climbs. Alberta's published examples use 2:1 and 3:1.
Nitrate-nitrogen (NO₃-N) sampled to 24 inches — 0–60 cm. This is deeper than Ontario's sample because nitrate moves down the soil profile, and a shallow core misses most of what the crop can actually reach. Make sure your lab report is the 0–24 inch value before entering it.
No. Alberta recommends the Modified Kelowna extraction; Ontario calibrates to Olsen. They return different numbers on the same soil and there is no reliable way to convert between them. Use the test your province's guidelines are built on.
Because Alberta has not published dryland response curves — they live only inside AFFIRM. Using the irrigated curves on a dryland field would overstate yield potential and over-apply nitrogen, so the tool declines to guess and points you to AFFIRM instead.
Yes. The published response tables assume 40 lb N/ac is released from soil organic matter during the growing season, so that credit is already built in. Do not subtract it again, and do not add a separate mineralisation allowance on top.
No. Soybeans fix their own nitrogen through Bradyrhizobium nodulation, and OMAFRA does not recommend fertilizer nitrogen for soybeans in Ontario. Applied nitrogen suppresses nodulation and rarely pays. Spend the money on inoculant for fields new to soybeans, and on potash where the soil test calls for it.
Ontario research found the most economic starter response when Olsen phosphorus sat between 12 and 18 ppm. Above roughly 30 ppm a phosphate response is rare, and above 60 ppm none is expected. Potassium behaves similarly, with the economic range around 100 to 130 ppm.
OMAFRA guidelines are calibrated to the Olsen (sodium bicarbonate) phosphorus extraction. Mehlich-3 and Bray-P1, standard across much of the United States, return different numbers that do not map onto Ontario recommendation tables. Use an OMAFRA-accredited laboratory.
It depends on three things, not one: the base requirement for your soil texture, your yield goal, and the credit for last year's crop. Corn following ploughed-down alfalfa can carry a credit of 110 kg N/ha — about 98 lb/ac. Ignoring that credit is the most common way Ontario growers over-apply nitrogen. The corn fertilizer guide sets out the full calculation.
Yes — completely free, with no account and no paywall.
Built for Canadian farming & sustainability
CropGPT is a free, practical tool that puts trustworthy agronomy in every grower's pocket. My ambition is to help Ontario and Canadian farmers cut input waste, protect soil and water, and make confident nutrient decisions — whether you read a soil report for a living or have never filled one out.
Every recommendation here is grounded in the OMAFRA Agronomy Guide for Field Crops (Publication 811) sufficiency guidelines, with transparent math you can check. It pairs an organic pathway (compost, manure, biologicals) with a synthetic pathway so you can compare both honestly — because sustainable farming is about choice, not dogma.
I'd love your feedback, corrections, and ideas. Reach me on LinkedIn:
Authentic Ontario sources — regulations, soil labs, weather & advisors. Every link goes to a government or association site.