Constraints of Organic Mulching

• As beneficial as organic mulch is, too much mulch can be harmful. A thick layer of organic mulch can be effective in suppressing weeds and reducing maintenance, but it often causes additional problems. Deep mulch can lead to excess moisture (root rot, mould fungus); it can create a habitat for rodents, which damage the plant. Furthermore, thick blankets of fine mulch may prevent penetration of water and air.
• Some organisms can proliferate too much in the moist and protected conditions of the mulch layer. Slugs and snails can multiply very quickly under a mulch layer.
• Ants or termites, which may cause damage to the crops also may find ideal conditions for living. When crop residues are used for mulching, in some cases there is an increased risk of sustaining pests and diseases.
• Damaging organisms such as stem borers may survive in the stalks of crops like cotton, corn or sugar cane. Plant material infected with viral or fungal diseases should not be used if there is a risk that the disease might spread to the next crop. Crop rotation is very important to overcome these problems.
• When carbon rich materials such as straw or stalks are used for mulching, nitrogen from the soil may be used by microorganisms for decomposing the material.Thus, nitrogen may be temporary not available for plant growth (risk of N-immobilisation).