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What Is Excess Soil Fertility, and How Is It Deducted?

Writer: Soil Deduction Advisors
Soil Deduction Advisors
Aug 24
3 min read

Section 180 isn't about how much your soil has produced. It's about the fertility that was already there when you bought the place. Here's what that actually means.


If you've read anything about Section 180, you've probably run into the phrase "excess soil fertility" without much explanation attached to it. It's the whole idea behind the deduction, and it's also the part most people get backwards.


Excess soil fertility has nothing to do with how much your land has produced, or how worn out your soil has gotten after years of farming. It's about what was already sitting in that ground, above a normal baseline, the day you bought or inherited the property. Get that straight, and the rest of Section 180 makes a lot more sense.


What Does "Excess" Actually Mean?

Every acre of farmland or ranchland needs a certain baseline of nutrients just to grow whatever's typical for that ground. Anything documented above that baseline is excess fertility. We're mainly talking phosphorus, potassium, lime, and a handful of micronutrients most people never think about. Nitrogen doesn't carry the same weight here, it doesn't stick around in the soil the way the others do.


That baseline isn't a number we pull out of thin air. It reflects what a typical operation on that ground actually needs in a given year. Anything above it is real, leftover value, built up over years of fertilizer application, natural soil makeup, or both.


Bar chart illustrating baseline versus excess soil fertility levels for phosphorus, potassium, lime, and micronutrients

Why "At the Time of Purchase" Matters

Here's where most people trip up. The excess fertility that counts for Section 180 is whatever was there the day you took ownership, not some running total of what your operation has used since.


Depletion does come into the calculation, that's how we work backward to figure out what the nutrient levels looked like on your purchase or inheritance date. But depletion is just the math we use to get there. It's not what you're deducting. What you're deducting is the excess value that was sitting in the ground the day you took over.


Timeline diagram showing that excess soil fertility is measured as of the purchase or inheritance date, not the present day

Which Nutrients Count?

Phosphorus (P), Potassium (K), Lime, Micronutrients (zinc, sulfur, boron, manganese)


Nitrogen mostly gets left out of this, or counted for very little. It just doesn't hang around in the soil long enough to add real excess value.


Checklist graphic showing phosphorus, potassium, lime, and micronutrients count toward excess fertility, with nitrogen excluded

How Is the Excess Value Measured?

We test the soil, measure the nutrients against a baseline for that soil type and land use, and value whatever's left over using regional pricing. If you bought the land a while back, we factor in depletion rates and any fertilizer you've put out since, so we can land on what the excess value actually was on the day you took ownership.


Sample nutrient heatmap showing excess soil fertility concentration across a property, from low to high

Why This Distinction Matters for Your Claim

Build a claim on the wrong foundation, treating it like a measure of production instead of the excess fertility that was there at purchase, and you're asking for trouble with the IRS. Getting this part right is what separates a legitimate, defensible report from a guess.


Comparison chart contrasting a defensible Section 180 claim with a guess-based claim

Find Out What's In Your Soil

If you've bought or inherited ag land and want to know what kind of excess fertility might already be sitting in that ground, a free consultation is the fastest way to find out.






This article is for educational purposes only and is not tax, legal, or accounting advice. Always consult your own CPA or tax advisor regarding your specific situation. Results vary based on soil conditions, land use, and applicable tax rules.


 
 
 

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