If half of your organic raised bed or container garden is made up of nutrient-rich compost/organic matter, fertilizer shouldn’t be necessary, especially if you you have used a blend of composts to fill your bed. If your soil is made up mostly of topsoil, however, fertilizer can give your bed an added boost.
A healthy garden is full of soil microorganisms, which include bacteria, fungi, nematodes and protozoa, as well as millipedes, beetles and earthworms. They break down the plant tissues and their waste adds to the organic matter of the soil, adding nutrients which will be readily absorbed by the plant roots. The microorganisms in the soil respond to organic matter with increased reproduction and growth, which enriches the soil further. Chemical (non-organic) fertilizers leave behind salt, which makes for an unwelcoming environment for the organisms that you need to hang out in your soil and add nutrients. The key is finding good organic fertilizers that will add the nutrients and minerals that your young raised bed doesn’t yet have in huge supply.
One of the best natural fertilizers is Vermicompost (yep, worm poop). Unlike regular compost, worm castings have insecticidal, antibiotics and fungicidal properties that help crops fight off disease and infestations of insects. Worm castings also release nutrients slowly, so you can put 1-2” in the bottom of each planting hole and know that it will continue to feed the plant for several months. A little goes a long way, and it’s not very expensive; you can get almost 5 lbs of Wiggle Worm Castings for about $12. Or, you can get yourself a Worm Factory Composter and get rid of your table scraps while harvesting valuable worm castings.
Coffee grounds are also a great organic fertilizer for acid-loving plants like roses and blueberries. We take the grounds from our morning coffee once a week or so and sprinkle around the base of our blueberry plants.
In past years, we have occasionally used a simple fertilizer to give all of the plants a boost halfway through the season.
Gardener’s Supply Company All-Purpose Fertilizer - This is a fertilizer designed to release slowly over the course of the season, and will not burn roots.
During the 2012 gardening season, we are trying out the product below:
Gardener’s Supply Company’s Organic Tomato Fertilizer - This product is similar to the All-Purpose Fertilizer, but has added phosphorus for large, abundant fruit.
And what could be better to add to the garden when your soil is low on compost? MORE COMPOST, of course:
Energy Buttons - This product is a mix of composted cow manure, composted chicken manure and calcium formed into pellets for easy distribution. Energy Buttons are designed to slowly release energy boosts over the entire season.