Coffee grounds can be beneficial for gardens, but they must be used carefully. While they can improve soil structure by adding carbon and bulk, they should not replace well-rotted compost or fertilizers. Linda Brewer, a soil scientist from Oregon State University, emphasizes moderation, stating, “A little is fine, a lot is probably not fine.” Excessive coffee grounds can be detrimental, as they contain caffeine, which can harm beneficial soil insects like earthworms.
For optimal use, apply no more than half an inch of coffee grounds to the soil surface, avoiding direct contact with the stems of plants. This small amount serves as a good carbon source for soil bacteria but is low in essential nutrients such as nitrogen, potassium, and phosphorus. Overusing coffee grounds could create an environment that repels earthworms while potentially keeping unwanted pests away, like slugs.
To improve the benefits of coffee grounds, Brewer recommends composting them alongside other kitchen and yard waste. This method enriches the soil and maintains microbial health through a diverse diet. Regularly monitor the compost for moisture and turn it occasionally. If composting is not feasible, sparingly sprinkle coffee grounds on your garden now and then, ensuring not to overload the soil.
In summary, while coffee grounds can be a useful additive in gardening, they should be used judiciously to avoid negative effects on soil health and plant growth. Balancing their use with other organic materials is key to maintaining a thriving garden ecosystem.
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