708 What Leaves the Farm … And What Comes Back?
Crops take nutrients off the farm. Can food-waste biostimulants bring them back? Are they worth your time and money? In this episode I’ll dig into nutrient imports, exports, how you can calculate the flows on your farm, and whether it’s worth trying some of the many products hitting the market.
So how has your winter been so far? It has finally come to my area. For many days I had walks in temperatures between -15C and -25C with frost covering the trees and any surface exposed to the air. Now we’re in the melt as the Chinook winds bring warm air. But there’s still lots of time for second winter to come before Christmas.
If you live south of Calgary, I’ll be speaking at an event this week put on by Foothills County. My talk is called: The Builder, The Banker, The Brewer: Balancing Soil Physics, Chemistry, and Biology in Prairie Fields.
It’s a free event on the afternoon of December 11th. Registration is at:
https://www.eventbrite.com/e/the-builder-the-banker-the-brewer-tickets-1968841229116
In case you’re new here, let me introduce myself. My name is Scott Gillespie and I’m an Alberta-based author, podcaster, and independent agronomy consultant that focuses on #RealisticRegenAg. I provide advice-only agronomic services to my farm clients —offering unbiased recommendations free from product sales. In this podcast I share science-based practices that that promote environmental stewardship and farm profitability.
What Leaves the Farm … What Comes Back?
Let’s start with what leaves the farm, because that’s the simplest part of the whole conversation.
Every time we harvest a crop, nutrients go with it. That part isn’t debatable. If nutrients were not leaving the farm the food would be of no value. We, and animals, eat it for the nutrients and energy it contains.
The tricky part is what we tell ourselves about how we replace those nutrients. When regenerative agriculture started gaining a lot of momentum in the mid-2010s, there was this growing belief that biology could do most of the heavy lifting, that if you did just the right things you could cycle enough nutrients to stay in balance.
It’s a beautiful idea. I understand why it resonated with so many people — it resonated with me too. But I kept stumbling over the math, especially around phosphorus. Biology can cycle nutrients. It can unlock some that are were never previously available. But it can’t magically replace what isn’t there.
On the Prairies, where our yields are high and improving, we remove far more nutrients in a season than biology can reliably supply on its own. This can work when the system is mostly closed – as it was when the bison roamed the land for thousands of years – but our system sends nutrients hundreds or thousands of kilometres away, never to return to the source.
Working with organic producers really reinforces this. Nitrogen can be built it with legumes if you take the land out of annual production for a year. But phosphorus? Unless manure or compost or something else enters the system, levels drift downward over time. Not dramatically in one year, but you can absolutely see the trend when you look at soil tests across five, ten, or twenty years.
Soil tests tell stories, and one of the clearest stories they tell is whether a farm is consistently replacing what it removes. Sometimes we think we are, and then the tests quietly say otherwise. To dive deeper into this, please check out the Better Farming Prairies article from this month: Imports vs. Exports: The only soil balancing you need to do.
https://www.betterfarming.com/flippingbook/better-farming-prairie/2025/october/48/index.html
Now, on the other side of the ledger is everything we try to bring back onto the farm. Historically, that’s been fertilizer or manure but over the last decade, that landscape has exploded.
Fertilizer prices shot up and suddenly every industry with a by-product — fish, forestry, food processing, municipalities — thought, “Maybe farmers will want this.”
And some of those products do make sense. Southern Alberta exports almost everything it produces. Very few nutrients come back in any meaningful way. So, the idea of waste-derived inputs — in principle — isn’t a bad one.
But then you get into the biostimulant world, and that’s where things get messy. These products don’t need proof that they work. By law, fertilizers must prove nutrient guarantees and pesticides must prove pest control. Biostimulants only need to show they’re safe.
That’s why we’re seeing so many new products on the market. Some are legitimately interesting. Some are recycled ideas with new branding. Many are “snake oil.”
The frustrating part is that some do work — but only in very specific circumstances. The timing has to be right, the crop stage has to line up, the weather needs to cooperate, and the application method matters. So even the products that have potential don’t always show it.
To dive deeper into this, please check out the Lethbridge County article: Nutrient Additives: Sorting the Value from the Hype
https://www.plantsdigsoil.com/s/Nutrient-Additives-Sorting-the-Value-from-the-Hype.pdf
The good news is that modern equipment makes testing easier than it has ever been. You don’t need a research trial. You don’t need flags in the field. You don’t need a clipboard. Autosteer and coverage maps let you create skip passes without the product and coming back to fill those passes in when you do have it.
You can get more scientifically rigorous with randomization and replication, but honestly, just a few skip passes and a treated area will tell you pretty quickly if there is an effect. Have you tried this? If you’ve been testing something new on your farm — whether it worked or didn’t — I’d love to hear about it.
Further Resources
Before I end today, I’d like to leave you with some resources.
First of all, if you want to know more about soil testing – go back to the last edition: Test Smarter to Spend Less: How soil tests help you buy the right fertilizer at the right time. I go over the common soil tests, including soil health tests, and what I look for when seeing a soil test.
If you want to get a feel for whether your system is replacing what is being sold off the farm each year, there are a couple of calculators available.
For a quick calculation check out the Prairie Nutrient Removal Calculator. You simply enter in the crop type and yield, and it will tell you how many nutrients go out in the grain. This doesn’t count what goes into growth that ends up staying on the field – the straw. Total uptake is higher, but this helps you to see how much leaves the field each year.
https://prairienutrientcalculator.info/
To get into more detail – and especially if you manage organically or use organic materials such as compost and manure – I’d encourage you to check out the Nutrient Budgeting App (which is actually just a webpage). For this you must think about everything that comes onto the farm and everything that leaves.
If you buy in feed and either feed on the field or spread the manure back to the field – this can be significant source of nutrients you are bringing back to the farm. You can still add in chemical fertilizers if you manage conventionally so you can get a complete picture. This has been a great addition to my consulting clients when we can see the flow of nutrients and focus our attention on the ones they are most short on.
https://pivotandgrow.com/resources/grain-resources/grain-production/nutrient-budgeting/
Closing remarks
Thanks for your attention! If something resonated let me know. I love to hear from you. Also, sharing this episode in your social networks, whether a post or to small group of your friends, colleagues, or clients, is very much appreciated. You can also support me by picking up a copy of my book, Practical Regeneration, or reaching out for agronomy support.
All the information can be found on my website:
www.plantsdigsoil.com
Here’s to growing more, believing less, and always digging a little deeper.
