Avoid excess crop nutrients in your fertilizer strategy to maintain soil health and protect your pocketbook


The push to produce higher yields per acre every year continues to weigh heavily on western Canadian farmers. That pressure is accompanied by economic and environmental concerns. Should you invest more money into crop nutrients to reach record yields? Will that investment pay off? Will excess nutrients run off and compromise soil health? If you’re facing this all-too-common dilemma, it’s a good time to revisit the Law of the Maximum.

In a nutshell, this law is a reminder that there is a maximum to your crop production. Therefore, when it comes to crop nutrient applications, your return on investment is proportional to the difference in value between your current production and your realistic maximum production goal.¹

More is not always better: Avoid wasteful excess using Mitcherlich’s Law of the Maximum

Also referred to as the “law of diminishing returns,” the Law of the Maximum considers a crop’s nutrient uptake and response to fertilizer strategy, particularly in reaching higher yield.² It measures the relation between a plant’s nutrient-specific growth increase to the ideal reduction you can take away from the maximum nutrient application while still achieving your yield goal. 

Our previous exploration of the Law of Minimum addressed the issues that accompany nutrient insufficiency playing a chief role in yield come harvest. In contrast, the Law of the Maximum speaks to excess in a particular nutrient and its limiting impact on yield. 

Should you overapply one nutrient in your soil, it’s likely to decrease the effectiveness of other essential nutrients. That means compromising your yield, and ultimately your profits off the combine. Furthermore, excessive nutrient accumulation can create toxicity in the plant. So, not only will yield be stunted, but quality also threatened.³ If you were to examine this concept on a graph, as you apply more fertilizer to overcome the level of a limiting factor, at a certain point you would see marginal productivity begin to fall off. ⁴

“Your yield curve can rise with the increase of nutrient, but there is that Law of Maximum,” says Garth Donald, Manager of Agronomy and co-founder at Decisive Farming by TELUS Agriculture. “You can keep going on that path, but once you’ve hit the maximum, the yield curve starts moving the other way. You will actually decrease yield because of that excess.”

Now, you’re at risk of losing valuable fertility investment dollars.

“While you’re applying at a high rate, it may not necessarily affect the plant. Moreover, it’s affecting your pocketbook,” says Donald. “Your cost to produce those extra bushels has become very expensive in trying to go from a 55-to-60-bushel canola crop, for example. If you’re in that type of area, maybe you are going over that yield curve. Will you get to 60 bushels? Probably, yes. But the cost to get there is astronomical compared to the return on investment.”

Balancing yield boost and economic investment

How can you reach the sweet spot of optimal fertility to defend your crops against disease, pests and adverse weather while also protecting your balance sheet? As we’re refreshing on the Laws of Minimum and the Maximum we also return to the 4-Rs. Because when we apply nutrients of the right source, in the right rate, at the right place and right time, we ensure soil health remains in constant balance.  

However, with so many factors at play, managing soil health – the foundation to a successful crop with higher yield – requires real time insight into what’s actually happening in that soil. By turning to new technologies, including comprehensive soil testing and accurate variable rate prescriptions, crop yield capabilities continue to move upwards beyond anything previously imagined. And that means money in the bank.


Have you discussed the Law of the Maximum with your agronomy professional to explore your ideal balance when it comes to higher yields and profits? Let’s talk today. 


¹ Ferreira, Zocchi and Baron. “Reconciling the Mitscherlich’s law of diminishing returns with Liebig’s law of the minimum. Some results on crop modeling.” Science Direct, Mathematical Biosciences
Volume 293, November 2017, Pages 29-37.

² Dhanoa et. al. “Overview and application of the Mitscherlich equation and its extensions to estimate the soil nitrogen pool fraction associated with crop yield and nitrous oxide emission.” Science Direct, Advances in Agronomy Volume 174, 2022, Pp. 269-295.

³ Hasanuzzamuan, Mirza. “Laws of Fertilizer Application.”

Hasanuzzamuan, Mirza. “Laws of Fertilizer Application.”