-DISC: How USDA Now Decides Whether You’re “No-Till” for 45Z
USDA has a calculator to determine if you really are No-Till
If you want a conservation-tillage practice to count toward your crop’s carbon intensity (CI) score under USDA’s new biofuel feedstock rule, you don’t eyeball it anymore. You run your field passes through USDA’s new Tillage Disturbance Index for Soil Carbon — T-DISC — and the tool tells you whether you’re no-till, reduced till, or conventional. T-DISC replaces the old STIR rating, and it only matters if you’re claiming a tillage practice on your CI score.
It’s a free macro-enabled Excel workbook, so enable macros when it opens. You only touch the “User Input” tab. Enter the date, farm, state, county, and crop (corn, soybeans, sorghum, or canola), and you can run up to 10 management units per file.
Then list every soil-disturbing pass across the crop interval — fertilization, tillage, residue and seedbed work, planting, and harvest. Spray passes that don’t disturb soil can be skipped. For each pass you pick a tillage window and the implement. The crop interval runs from one day after your prior crop’s harvest to harvest of the feedstock crop, split into five windows: Field Preparation, Before Planting, Planting, After Planting, and Harvest.
Here’s the part that trips people up: your rating is the single worst window, not an average. The tool scores each window from 0 to 1 and takes the maximum. One heavy pass in any window sets your designation. The thresholds:
