Green manure involves planting specific crops that pull nitrogen from the air and pump it into the soil to serve as a natural fertilizer. By cutting these mature plants and mixing them into the soil, farmers can drastically reduce the need for synthetic inputs.
What Is Green Manure?
Green manure describes the practice of using cover crops as a natural fertilizer source. Instead of purchasing expensive chemical fertilizers, farmers plant species that naturally capture atmospheric nitrogen. When the crops reach maturity, they are cut and integrated into the topsoil to provide a nutrient boost for the main planting cycle. This process acts as an effective way to help farmers in Mozambique achieve higher yields without the overhead costs of chemical urea.
Best Green Manure Crops for Mozambique (Asian Origin)
| Crop | Origin | N Fixed (kg/ha) | Growth Time | Drought Tolerant |
|---|---|---|---|---|
| Sunhemp (Crotalaria) | India | 80-120 | 60 days | Yes |
| Sesbania | India/SE Asia | 100-150 | 60-90 days | Yes |
| Mucuna (velvet bean) | Asia | 120-170 | 90-120 days | Yes |
| Cowpea (feijão) | Asia/Africa | 60-80 | 60 days | Yes |
| Pigeon pea | India | 60-90 | 90-150 days | Yes |
| Gliricidia | Central America | 50-80 | Perennial | Yes |
| Tephrosia | Africa/Asia | 40-60 | 60-90 days | Yes |
The Economics of Natural Fertilizers
| Fertilizer Source | Cost/Hectare | Nitrogen Provided |
|---|---|---|
| Urea (chemical) | $50-100 | 50kg |
| Sunhemp (green manure) | $2 | 80-120 kg |
| Mucuna (green manure) | $3 | 120-170 kg |
| Cowpea (green manure + food) | $4 | 60-80 kg |
Cowpea is particularly valuable because it provides free nitrogen and up to 500kg of edible beans. This dual-purpose strategy allows a farmer to fertilize the soil while simultaneously feeding their family.
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The Seasonal Impact on Smallholders
For a smallholder farmer in Zambezia working with the COJAZ cooperative, adopting green manure changes the rhythm of the season. By planting legumes at the start of the rains in October, the farmer creates a biological factory in the field. This preparation period ensures that when the main crop, such as maize or cassava, is planted in January, the soil is enriched with nitrogen, leading to more robust growth during the critical rainy months.
How to Use Green Manure in Mozambique
| Step | Action | Timing |
|---|---|---|
| 1 | Plant at start of rains | October |
| 2 | Let grow 60 days | Oct-Dec |
| 3 | Cut at flowering | December |
| 4 | Mulch or incorporate | December |
| 5 | Wait 2 weeks for decomposition | December |
| 6 | Plant main crop | January |
| 7 | Main crop benefits | Jan-April |
Related guide: Climate-smart agriculture in Mozambique: 6 technologies helping farmers beat drought, floods and cyclones
Frequently asked questions
Why is nitrogen important for soil? Nitrogen is a primary nutrient that fuels plant growth, making it essential for high yields in staple crops like maize.
Does green manure require special machinery? No, these crops are typically managed by hand, making them highly accessible for smallholder farmers.
Can these crops grow in dry conditions? Many of the species listed, such as sunhemp and cowpea, are known for their high drought tolerance, which is critical for Mozambican climates.
Maputo Bridge Capital, founded by Anselmo Boaventura in Fort Worth, Texas, supports smallholder farmers in Mozambique by connecting sponsors with verified local producers. A sponsorship gift of $25 provides direct support to the farmer's local seed and fertilizer shop; the sponsor receives photos and receipts as proof of the gift. These sponsorships are gifts, not investments, and are not tax-deductible. To learn more or to support a farmer, visit sponsor a farmer.