How to fertilize tomato plants with coffee grinds?

Coffee grounds added to compost and used in the garden as organic fertilizer give your plants a boost, attract earthworms and may deter both slugs and insect pests in the garden. However, the notion that the acidity in the coffee grounds will lower the pH of the soil, making them ideal for acid-loving plants, doesn’t always hold true, says Linda Chalker-Scott, Ph.D. Master Gardner, editor and associate professor from the Washington State University Extension. While some coffee grounds are acidic, some are neutral to alkaline. Soils treated with coffee grounds actually increase in pH for the first three weeks and then gradually decline.

1. Add used coffee grounds to the compost bin, but don’t over do it. Keep coffee grounds to no more than 20 percent of the material included in your compost. Coffee grounds are considered green material, like fresh grass clippings and kitchen waste, and must be balanced with brown material, such as dried leaves, to compost properly.
2. Spread a one-half-inch layer of used coffee grounds around the base of your tomato plants and top with 2 to 3 inches of organic mulch. According to Washington State University Extension, coffee grounds compact easily and prevent good air circulation when used in thicker layers, but a thin layer gives your tomatoes a boost of nitrogen.
3. Sprinkle 1 cup of used coffee grounds around the base of your tomato plant and work it into the top 2 to 3 inches of soil with a trowel or claw. This encourages the coffee grounds to begin decomposition and prevents issues with soil compaction.Add well-composted coffee grounds to the planting hole when transplanting tomato seedlings to improve soil composition and provide a source of slow-release nutrients to your plants.
4. Mulch around tomatoes with composted coffee grounds throughout the summer to conserve moisture, prevent weeds and add nutrients to the soil.
5. Till coffee grounds into the soil in the fall and allow them to decompose right in the soil. The University of Florida Extension recommends amending the soil with organic matter such as compost, manure or coffee grounds twice a year.
6. Mix one part coffee grounds to one part soil for container-grown tomatoes.