Surprising Superfoods for Your SoilBy Benedict Vanheems | December 4, 2021
As gardeners, we often seek ways to enrich our soil using natural, sustainable resources. In this article, we’ll explore four everyday kitchen and household waste products that can significantly improve your soil’s fertility — and the best part? They’re free!
1. Coffee Grounds: A Slow-Release Nitrogen Boost
Coffee grounds are a fantastic, underutilized garden resource. They provide nitrogen, phosphorus, potassium, and essential micronutrients like magnesium, copper, calcium, and iron. While nitrogen is slow to become available to plants, the microbes in your soil gradually break it down, offering a steady nutrient supply.
To use coffee grounds effectively, don’t dig them into the soil, as some plants, like tomatoes, may not respond well. Instead, scatter them lightly on the soil surface or use them as mulch around your plants. This prevents the grounds from forming a hard crust, allowing water to penetrate more easily.
The pH of coffee grounds ranges from 6.5 to 6.8, which is ideal for most vegetables. Even though they are slightly acidic, when spread thinly, they won’t significantly alter your soil’s pH.
Coffee grounds are also a great addition to compost piles, where their nitrogen content accelerates decomposition. They balance the ‘browns’ (like leaves or straw) and help generate heat, speeding up the composting process. Don’t forget — worms love coffee grounds too!
2. Eggshells: A Calcium-Rich Fertilizer
Eggshells are a powerhouse of calcium and trace minerals like magnesium. Rather than buying expensive soil amendments, repurpose your eggshells by grinding them into a fine powder. This makes the calcium more accessible to plants over time.
To prepare eggshells, rinse them thoroughly to prevent contamination, and then sterilize by heating them in the oven or microwave. Once dry, crush them or grind them into powder using a blender or coffee grinder. Apply this powder directly to your garden beds, especially those growing fruiting plants like tomatoes, peppers, and zucchini. Calcium helps prevent blossom-end rot, a common issue in these crops.
Worms also benefit from powdered eggshells as they aid digestion and act as grit, promoting healthy soil and compost. If you have a compost pile, add crushed eggshells to nourish worms and boost decomposition.
3. Wood Ash: A Fertilizer Rich in Potassium and Phosphorus
Wood ash from untreated wood is a valuable source of nutrients such as potassium, phosphorus, calcium, and magnesium. It also contains biochar — the porous, carbon-rich material created when wood is burned — which supports soil microbes and enhances soil structure.
Wood ash can be sprinkled on garden beds, but be cautious: it’s highly alkaline, so avoid using it around acid-loving plants like blueberries or rhododendrons. It’s also not suitable for potatoes, as it can promote potato scab. However, it’s perfect for plants like broccoli, which prefer slightly alkaline soil, and can be used as a substitute for lime to neutralize acidic soils.
Adding wood ash to your compost heap is another great option. It reduces acidity, improves microbial activity, and contributes to overall soil fertility. Just be sure the ash has cooled completely before handling.
4. Tea Leaves: Another Natural Addition
Tea leaves, much like coffee grounds, are packed with nutrients and can be added to compost or used as mulch. However, avoid adding teabags that contain plastic. Opt for biodegradable ones if you choose to add the whole bag.
Conclusion
These four “superfoods” — coffee grounds, eggshells, wood ash, and tea leaves — are easy-to-obtain, eco-friendly ways to boost your soil’s fertility. By reusing everyday waste products, you not only enrich your garden but also contribute to a more sustainable, zero-waste lifestyle. So, the next time you brew a cup of coffee, crack an egg, or use firewood, remember that these common materials can help you grow a healthier, more productive garden. Happy gardening!