Soil Carbon Amendment Standard
Citation: USDA Natural Resources Conservation Service (2022). Conservation Practice Standard: Soil Carbon Amendment, Code 336. November 2022. https://www.nrcs.usda.gov/sites/default/files/2022-11/336-NHCP-CPS-Soil-Carbon-Amendment-2022.pdf · mirror: NRCS Azure copy
What it is: The national practice standard behind US cost-share payments for biochar and compost. It sets the product requirements; planning details are in answers CPS 336 planning questions.
Key figures
| Figure | Value | Where | Check |
|---|---|---|---|
| What counts as biochar | Biomass heated above 350 °C under controlled, limited oxygen (pyrolysis or gasification) | Standard PDF (mirror), biochar criteria | ✓ full text |
| Organic carbon | >10% dry weight | Standard PDF (mirror), Table 3 | ✓ full text |
| H:C_org | <0.7 (molar ratio) | Standard PDF (mirror), Table 3 | ✓ full text |
| Report-only parameters | Total ash; liming equivalent (% CaCO₃) | Standard PDF (mirror), Table 3 | ✓ full text |
| Metals | Maximum limits, e.g. chromium <1,200 mg kg⁻¹ dry weight | Standard PDF (mirror), Table 3 | ✓ full text |
| Labs | Labs meeting IBI Seal performance requirements, or an alternative state-approved certification program | Standard PDF (mirror), below Table 3 | ✓ full text |
| Inoculation | Inoculate biochar with compost, compost tea, or manure, to balance nutrients, stabilize pH, and improve moisture for application | Standard PDF (mirror) | ✓ full text |
| Carbon goal | Use low H:C_org biochar (<0.7) to maximize soil carbon sequestration | Standard PDF (mirror) | ✓ full text |
| Compost pathogen limits, for comparison | Fecal coliform <1,000 MPN g⁻¹; Salmonella <3 MPN per 4 g (dry compost) | Standard PDF (mirror), compost table | ✓ full text |
| Raw manure and biosolids | Manage under Nutrient Management (Code 590) | Standard PDF (mirror), general criteria | ✓ full text |
Use with care
- Standards are revised periodically. Check the NRCS Field Office Technical Guide for the current version before quoting thresholds.
- In the 2022 text, a search for biosolids only turned up a pointer to Nutrient Management (590). The exclusion of biosolids-derived biochar and compost is stated in answers CPS 336 planning questions.
- The nrcs.usda.gov link failed to download during this check; the Azure mirror above served the same document.
Related: NRCS soil carbon amendment in US ag · Product Standards EBC IBI · Key Sources