An organic garden must start with healthy soil. Natural fertilizers promote the growth of beneficial bacteria, earthworms and fungi which build soil structure and foster healthy plants.
The best fertilizer for your lawn and garden is homemade compost, made from food scraps, fall leaves and lawn clippings. If you still need store-bought products, there are some things to keep in mind.
Commercially made compost has a high level of naturally occurring nitrogen and phosphorous which is released gradually and is absorbed more easily by plants. Other soil improvers, such as worm castings, Epsom salts and decomposed organic matter called humates, add nitrogen, phosphorus and potassium. Watch out for commercial fertilizers, even those that are labeled “organic”, because they most likely contain harmful ingredients, like animal byproducts or sewage sludge. Animal byproducts, such as bone meal or fish meal, may have come from industrial farming operations, and sewage sludge, might be contaminated with diseases or heavy metals.
The Organic Materials Review Institute (OMRI) and the Northeast Organic Farming Association (NOFA), an accredited certifying agency for the USDA National Organic Program, approve of products which have been composted according to USDA Organic standards. The only synthetic materials that can be added to NOFA approved compost are those allowed in the production of organic crops.
Have your soil tested by your local USDA Cooperative Extension Service to determine pH and which nutrients your grass is missing, or test it yourself with a soil testing kit.
Once you know the pH, you may add organic matter to help balance it. Lawns prefer slightly acidic soils with a pH range of 6.5 to 7, while flowers, shrubs and trees vary in their pH preferences. Lime helps balance acidic soil, while sulfur helps with alkaline.
To find out the nutrient content of a fertilizer, look for the “NPK” number (NPK stands for nitrogen, phosphorus and potassium). A “5-6-5” NPK number, for example, means that a fertilizer is 5% nitrogen, 6% phosphorus and 5% potassium with the remaining 84% representing filler material.
Spread only about 1/2 an inch of compost on your lawn at a time. Even though plant-based nitrogen is more easily absorbed, composts and organic fertilizers may still be applied too heavily, leading to nitrogen- and phosphate-heavy runoff.
Avoid applying fertilizer before a downpour which will rinse it away before it gets absorbed. Wear a mask if you are applying dusty fertilizers made with lime or any other fine particles that you might inhale.