What Is Solarization?
Solarization is an agricultural technique that involves covering moist soil with clear plastic for 4-6 weeks during the hottest months. The sun heats the soil to temperatures between 40-50°C, which effectively kills weed seeds, soil-borne diseases, nematodes, and insect pests without the need for chemicals.
What Solarization Kills
| Pest/Disease | Killed at 40°C | Killed at 45°C | Killed at 50°C |
|---|---|---|---|
| Weed seeds | 7 days | 3 days | 1 day |
| Nematodes | 14 days | 7 days | 2 days |
| Fungal pathogens | 14 days | 7 days | 3 days |
| Bacterial pathogens | 21 days | 10 days | 5 days |
| Soil insects | 7 days | 3 days | 1 day |
Mozambican Solarization Calendar
| Month | Soil Temp (under plastic) | Effectiveness |
|---|---|---|
| October | 38-45°C | ✅ Good |
| November | 42-50°C | ✅ Excellent |
| December | 45-55°C | ✅ Perfect |
| January | 45-55°C | ✅ Perfect |
| February | 42-50°C | ✅ Excellent |
Mozambique possesses 5 months of perfect solarization conditions, providing a significant advantage over most other countries that only experience 1-2 months of sufficient heat.
Solarization and the Farmer's Season
For a smallholder farmer in Zambezia, solarization creates a clean slate for the planting season. By utilizing the intense heat of October through February, farmers can prepare their plots to be free of weeds and soil-borne pathogens before planting begins. This reduces the burden of manual weeding and protects young crops from diseases, leading to higher yield potential.
The Nature of Mozambican Agricultural Land
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Cost and Savings
| Item | Cost |
|---|---|
| Clear plastic sheet (200 microns, 1 hectare) | $50-100 |
| Labor (lay plastic, 1 day) | $0 |
| Wait 4-6 weeks | $0 |
| Remove plastic | $0 |
| Total per hectare | $50-100 |
| Benefit | Value |
|---|---|
| No herbicide needed | Saves $30-50/ha |
| No nematicide needed | Saves $50-100/ha |
| No soil fumigation | Saves $100-200/ha |
| Yield increase (clean soil) | +20-50% |
Related guide: Climate-smart agriculture in Mozambique: 6 technologies helping farmers beat drought, floods and cyclones
Frequently asked questions
What makes solarization effective? Solarization uses the sun's radiation trapped under plastic to reach temperatures that neutralize harmful soil organisms.
Does solarization affect all soil types? It works best on moist soil, as moisture is essential to help conduct heat into the deeper layers where pests reside.
Can solarization be used for every crop? It is a pre-planting soil treatment that benefits a wide range of crops by creating a healthier, pest-reduced environment before seeds are sown.
Maputo Bridge Capital, founded by Anselmo Boaventura in Fort Worth, Texas, works with the COJAZ cooperative in Zambezia to support local agriculture. You can sponsor a farmer from $25 to provide them with the seeds and fertilizer they need for a successful harvest. Please note that sponsorships are gifts, not investments, and are not tax-deductible.