45Z for Corn Growers: The Nitrogen You Don’t Apply Now Counts

Written with expertise provided by Erik Wolfe, Product Marketing Director, Sound Agriculture

If you sell corn to an ethanol plant, your fertility plan now shows up in that plant’s tax credit. Under the federal 45Z clean fuel credit, ethanol plants earn more per gallon when the fuel they make has a lower carbon score. Since September, part of that score can come from your field instead of a national average, and the biggest piece of a corn field’s score is nitrogen. 

That puts a new number on a decision you already make every year. Fertilizer goes down when the ground allows, not when the crop needs it, so many plans carry extra pounds to cover what gets lost or tied up before the crop can use it. Sound Agriculture puts an active soil to work on every acre, and with Maximum Acre you can replace up to 35 lbs of nitrogen and phosphorus. Under 45Z, every pound of nitrogen you leave off can also lower the carbon score of the corn you sell. 

Here’s what changed, what a lower score can be worth, and how to set up your 2027 nutrient budget so it counts. 

45Z is a federal tax credit paid to fuel producers, including ethanol plants, for each gallon of low-carbon fuel they make. The lower the fuel’s carbon intensity (CI) score, the larger the credit. In 2026 it is worth up to $1.09 per gallon, and it covers fuel sold through the end of 2029.

What Changed with 45Z This Fall? 

Until this fall, every plant had to count its corn at a national default score, no matter how the corn was grown. On September 8, 2026, the IRS (Notice 2026 – 53) and the Department of Energy opened the door to field-level scores. A plant can now replace the default with scores calculated for individual fields in USDA’s Feedstock Carbon Intensity Calculator (FD-CIC). Growing the corn is more than half of a typical plant’s score, so for plants without carbon capture, the farm is now the biggest lever left.

The first payments are already reaching farmers. In late October, Marquis announced more than $10 million in 45Z payments to 350 farmers for practices like reduced tillage, cover crops and nutrient management. For most growers though, the 2027 crop is the first real chance to plan for 45Z. Treasury’s final rules are expected in November 2026, and most plants are still building their low-CI grower programs, with 2027 nutrient budgets being written now. 

How the USDA Calculates Your Corn’s Carbon Score

USDA’s Feedstock Carbon Intensity Calculator scores each field from what goes on it and what comes off. It adds up the fuel, fertilizer and other inputs used to grow the crop, divides by the bushels harvested, then gives credit for practices that store soil carbon or cut emissions. Four things move a corn field’s score: 

• Nitrogen per bushel. This is the biggest piece. About 61% of corn’s default score moves with your nitrogen rate, from the energy used to make the fertilizer to the nitrous oxide released after it goes on (based on USDA’s national default, every field is different). Fewer pounds per bushel means a lower score.
• Tillage. No-till and reduced till earn soil-carbon credit.
• Cover crops. A cover crop earns its own soil-carbon credit, on top of tillage.
• Nitrification inhibitors. These lower the nitrous oxide from the nitrogen they treat. 

What isn’t scored matters too. The calculator has no entry for soil activators, biologicals or inoculants, and phosphorus doesn’t change the score. SOURCE by Sound Agriculture lowers your score only through the nitrogen it lets you leave off, so the value is earned only when you take the cut. 

What Each Practice Could Be Worth

The plant compares your whole field to a national default score, and each CI point below that default is worth about 6¢ per bushel of 45Z value. Practices add up on the same field.

Just being scored can be worth something. A central Iowa field at 200 bu/​ac and 180 lb of nitrogen already scores a little better than the default, so documenting it earns value with no changes at all. Fields with fewer pounds of nitrogen per bushel start further ahead, and in a few counties the same field scores slightly worse than the default.

Sound modeling in USDA’s FD-CIC v1.2 for a Story County, Iowa field at 200 bu/​ac and 180 lb of nitrogen with conventional tillage. Each practice row is what it adds on top of being scored. Values are the gross credit a lower score creates in the fuel chain at the 2026 rate of $1.09/gal, not a payment to the grower. Your county, yield and starting rate will change the numbers.

Keep two things in mind. First, this is the value a lower score creates for the plant. How much reaches you depends on the plant’s grower program, and programs will differ in how and what they pay. Second, 45Z value is separate from any fertilizer savings. The pounds you don’t buy pay you back whether or not your plant runs a program.

Maximum Acre: A Lower Score Without a New Practice

No-till and cover crops earn real credit in the calculator, and they are worth doing where they fit your operation. They also ask you to change how you farm. Maximum Acre lowers your score without adding a practice, because it changes the one input the calculator weighs most.

Maximum Acre is a chemistry and biology system to maximize a crop’s access to nutrients, all season long. SOURCE is a foliar chemistry that activates beneficial microbes to mobilize N, P and micronutrients, applied at 1 oz/​ac in a pass you already make. BLUEPRINT is beneficial fungi that extend the root system to reach more nutrients in the soil, applied at planting. Together, BLUEPRINT extends the reach and SOURCE increases available nutrients.

That is what lets you replace up to 35 lb of synthetic nitrogen and phosphorus with SOURCE and BLUEPRINT while still improving yields.

The cut is backed by the Fertilizer Replacement Guarantee. Qualifying corn growers who replace synthetic nutrients with an application of SOURCE or SOURCE & BLUEPRINT will achieve a return on investment equal to or greater than the price of the product, or we will refund the difference. Restrictions apply.

What it could be worth. On the same central Iowa field, a full 35 lb nitrogen cut with Maximum Acre lowers the score about 3 CI points. That is worth about 19¢ per bushel, or $38 per acre, of 45Z value at the plant. It adds on top of any practices the field already earns credit for, and it is separate from the fertilizer you don’t buy.

How to Get Your Nitrogen Cut Counted in 2027

Sound’s part comes at step 2, in the nutrient budget. Scoring and verification stay with the plant and its partners.

1. Ask your grain buyer about the 2027 crop. Find out whether the ethanol plant or elevator you sell to is running a low-CI grower program, how it scores fields and how it pays. Supply sheds overlap, so a documented nitrogen cut can count at whichever participating plant buys your corn.
2. Write the cut into your nutrient budget before nitrogen goes on. Starting with the 2027 crop, a scored field needs a pre-application nutrient budget, based on a soil test less than two years old or prepared by a qualified, independent agricultural expert. That budget is where Maximum Acre gets written in, with your nitrogen rate set to match.
3. Take the full cut and keep your records. The calculator credits the nitrogen you actually apply against the yield you harvest. Programs require five years of records and an attestation that the field’s carbon benefits aren’t sold into more than one market.
4. Enroll through the plant’s program. Scoring and verification run through the plant and its partners. Your lower nitrogen rate shows up as a lower score, with no separate Sound enrollment.

For Ethanol Plants

Nitrogen per bushel is the one lever that reaches every acre in your supply shed. Maximum Acre gives your growers a way to lower their scores on conventional, reduced-till and no-till fields alike, with fertilizer savings and a guarantee that make the cut easier to say yes to.

Growers are writing 2027 fertility plans now. Talk to your local Sound dealer about writing Maximum Acre into your nutrient budget, and visit sound.ag/45z to see what a nitrogen cut could be worth on your acres. Visit How to Buy for more information.