Mulches reduce plant diseases by reducing soil splashing, influencing the moisture content and temperature of the soil, and enhancing the microbiological activities that suppress plant pathogens. In the hot humid tropics, where plant growth is rapid and luxurious, the use of green manures and natural vegetation as mulches (as in the slash/mulch system) should be considered, as their use provides an effective management practice for some diseases.
Farmer in Jamaica bringing grass mulch to his scallions (Picture courtesy Dennis Finney)
Mulching means different things to different people. It has been simply defined as "application of a covering layer of material to the soil surface or "any covering placed over the soil surface to modify soil physical properties, create favorable environments for root development and nutrient uptake, and reduce soil erosion and degradation". Webster's dictionary defines mulch as "leaves, straw, or other loose material spread on the ground around plants to prevent evaporation of water from soil, freezing of roots, etc." Covering seems to be a key word in most definitions. Soil erosion is a major environmental problem throughout the developing world. The problem is increasing rapidly, not only because more land is being cleared, but because farmers are being forced onto steeper, more fragile lands as arable land on gentle slopes becomes unavailable. Soil losses of hundreds of tons per hectare per year are common on steep slopes with some annual crops. The use of various soil covers, especially mulches, to reduce erosion is becoming recognized as one of the most effective strategies for reducing soil erosion on steep hillsides. The MOIST group has information on mulches, cover crops, green manures, and managed fallows in tropical farming systems.
Raised bed in chinampa mulched with grass (Picture courtesy of Alan G. Turner)
Compost pit for human and animal waste (foreground) in China. Mulched raised beds in back. (Picture courtesy of Steve Risch)
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More traditional agricultural methods :
| Mulching |
| Slash/Mulch | Frijol Tapado / Web Blight |
| Manipulating Shade | Burning | Flooding |
| Multiple Cropping | Using Organic Amendments |
| Rotations | Fallow | Raised Beds |
| Crop Diversity | Storage Practices |
| Multistory Systems |
Comments and suggestions welcomed ...