Many people choose to place coffee grounds straight onto the soil and use it as a fertilizer. Remember that while coffee grounds add nitrogen to your compost, they will not immediately add nitrogen to your soil. The benefit of using coffee grounds as a fertilizer is that it adds organic material to the soil, which improves drainage, water retention, and aeration in the soil. The used coffee grounds will also help microorganisms beneficial to plant growth thrive as well as attract earthworms.
Many people feel that coffee grounds lower the pH (or raise the acid level) of soil, which is suitable for acid-loving plants. This is only true for unwashed coffee grounds though. Fresh coffee grounds are acidic. Used coffee grounds are neutral. If you rinse your used coffee grounds, they will have a near-neutral pH of 6.5 and will not affect the acid levels of the soil. To use coffee grounds as fertilizer, work the coffee grounds into the soil around your plants. Leftover diluted coffee works well like this too.
Read more at Gardening Know How: – Used Coffee Grounds For Gardening https://www.gardeningknowhow.com/composting/ingredients/coffee-grounds-gardening.htm