What is Mulch?
Mulch is a protective blanket of material placed on the soil surface. In tropical agroforestry, mulch is most often produced by pruning nitrogen-fixing shade trees and spreading the leaves and small branches around crop plants.
Types of Mulch
Organic Mulch
- Leaf litter: Naturally falling leaves from canopy trees.
- Green mulch: Fresh prunings from hedgerows or shade trees.
- Wood chips: Chipped branches and bark.
- Compost: Partially decomposed organic matter.
Living Mulch
- Ground covers: Low-growing plants that blanket the soil (e.g., tropical legumes like Arachis pintoi).
Benefits
- Moisture retention: Reduces evaporation by 25–50%.
- Temperature moderation: Keeps soil 5–8°C cooler in direct sun.
- Weed suppression: Blocks light needed for weed germination.
- Nutrient release: Decomposing mulch slowly releases nitrogen, phosphorus, and potassium.
- Erosion control: Protects soil from raindrop impact and surface runoff.
Mulch from Costa Rican Trees
Madero Negro (Gliricidia sepium)
Prunings decompose quickly, releasing nitrogen within 2–4 weeks — ideal for fast-growing crops.
Guaba (Inga edulis)
Leaf litter is abundant and nutrient-rich; traditional shade-tree prunings are used as mulch in coffee plantations.
Guarumo (Cecropia spp.)
Large leaves make excellent short-term mulch in restoration plantings.
Application in Costa Rica
- Coffee farms: Shade-tree prunings provide most or all mulch needs.
- Home gardens: Kitchen scraps plus tree prunings mulch vegetable beds.
- Restoration sites: Mulch around newly planted seedlings dramatically improves survival rates.