The Five ALM Practice Categories in Depth
Key takeaway
The "what" of a VM0042 project
Every VM0042 project must implement at least one of these five practice categories. Understanding each category, including its mechanism, examples, and which GHG it primarily affects, is essential for project design.
Category (a): Fertilizer Management
Mechanism: Reducing nitrogen inputs decreases N₂O emissions from soil nitrification/denitrification. Adding organic amendments increases carbon inputs to soil, raising SOC.
Example practices:
- Reduce synthetic N fertilizer application rate by ≥5%
- Switch to slow-release or enhanced-efficiency fertilizers
- Replace synthetic N with compost or manure
- Use nitrification inhibitors
Worked example
📍 Vietnam Rice: A cooperative reduces urea from 200 → 140 kg N/ha/yr (30% reduction). N₂O emissions drop by ~25%. They also add 2 t/ha composted rice straw, increasing SOC inputs.
Category (b): Water Management / Irrigation
Mechanism: Reducing flooding in rice paddies dramatically cuts CH₄ from anaerobic decomposition. Efficient irrigation can improve crop biomass returns to soil.
Example practices:
- Alternate Wetting and Drying (AWD) in rice
- Switch from flood to drip/furrow irrigation
- Deficit irrigation strategies
Worked example
📍 Philippines Rice: AWD, draining paddies mid-season instead of continuous flooding. CH₄ emissions drop by 30–50%. This is one of the highest-impact practices in VM0042.
Category (c): Tillage / Residue Management
Mechanism: Less tillage = less soil disturbance = less SOC oxidation. Residue retention = more organic matter input to soil.
Example practices:
- Switch from conventional to no-till or reduced till
- Retain crop residues on field instead of removing or burning
- Change from fall to spring tillage
Worked example
📍 India Wheat: Punjab wheat farmers switch from burning rice stubble (massive air pollution) to "happy seeder" technology, planting wheat directly into standing rice residue. Residue remains on field, adding ~1.2 tC/ha/yr to SOC.
Category (d): Crop Planting & Harvesting
Mechanism: More continuous ground cover and root biomass = more carbon inputs. Agroforestry adds woody biomass carbon (tracked separately).
Example practices:
- Planting cover crops in fallow periods
- Agroforestry (trees integrated into cropland)
- Diversified crop rotations (adding legumes, perennial phases)
- Improving species selection in perennial grasslands
Worked example
📍 US Corn Belt: Corn farmers plant cereal rye as winter cover crop after corn harvest. Rye grows through winter, is terminated in spring, and its biomass decomposes into the soil, depositing approximately 0.5–1.0 tC/ha/yr additional carbon.
Category (e): Grazing Practices
Mechanism: Managed grazing allows grass recovery and deeper root growth, increasing SOC. Reduced stocking can lower enteric fermentation (CH₄) and manure (N₂O + CH₄) emissions.
Example practices:
- Rotational grazing / adaptive multi-paddock grazing
- Reducing stocking density on overgrazed land
- Replacing continuous grazing with seasonal rest periods
Worked example
📍 Patagonia, Argentina: A cattle ranch shifts from continuous grazing to planned rotational grazing (60–90 day rest periods). Grass root depth increases from 10 → 30 cm, dramatically increasing belowground carbon inputs. SOC gains: 0.8–1.5 tC/ha/yr.
Analogy
🎸 Analogy: A Band vs. a Solo Act
A single practice category is like one musician. Stacking multiple categories is like forming a band, the combined effect is far greater than each individual contribution. Conservation Agriculture (no-till + cover crops + residue retention) is the "band" most often seen in VM0042 projects because it hits SOC, fossil fuel, and N₂O reduction simultaneously.
Multiple Practices = "Stacked" Benefits
Projects can combine multiple practice categories. Common "stacks":
| Practice Stack | Categories | Combined GHG Benefit |
|---|---|---|
| Conservation Agriculture | (c) no-till + (d) cover crops + (c) residue retention | ↑ SOC, ↓ fossil fuel, ↓ N₂O |
| Climate-Smart Rice | (b) AWD + (a) N management + (d) improved varieties | ↓ CH₄, ↓ N₂O, ↑ SOC |
| Regenerative Ranching | (e) rotational grazing + (d) improved grasses + (a) reduced synthetic N | ↑ SOC, ↓ CH₄, ↓ N₂O |
Key Takeaways
- The five ALM categories are: (a) fertilizer management, (b) water/irrigation, (c) tillage/residue, (d) crop planting/harvest, and (e) grazing practices
- Stacking multiple categories (e.g., no-till + cover crops + residue retention) produces far greater carbon benefits than any single practice alone
- Category (c) tillage/residue and (d) crop planting are the most common in current VM0042 projects worldwide
- Rice AWD (Alternate Wetting and Drying) under category (b) is one of the highest-impact single practices, cutting CH4 by 30-50%
- Each practice category has a primary GHG mechanism - understanding which gas each lever affects is essential for accurate project boundary design
Knowledge Check
Test what you just learned
3 questions · check each one as you go
A project in the Philippines implements 'Alternate Wetting and Drying' (AWD) in rice paddies. Which category does this fall under, and what is the primary GHG benefit?
What makes 'conservation agriculture' a 'stacked' VM0042 project?
A project wants to reduce stocking density on degraded grassland. What is the main SOC mechanism at work?