All About Organic Garden Fertilizers

Natural sources of soil nutrients are available for free, yet in some instances you might want to buy supplemental fertilizers. Use this guide to build your soil’s nutrient content and save money over high-priced commercial fertilizers.

| May/June 2015

  • Pesticide-free grass clippings are one of the best fertilizer options.
    Photo by GAP Photos
  • To maintain tomato productivity, add a light application of organic fertilizer and a fresh helping of grass clippings around midsummer.
    Photo by GAP Photos
  • Spread a 1⁄2- to 1-inch layer of compost into your soil before planting each crop.
    Photo by iStock

As more and more people recognize the benefits of organic gardening methods, a fresh crop of organic fertilizers is sprouting up on garden-store shelves. Many are overpriced, and some are stunning rip-offs that reputable stores and catalogs shouldn’t sell. The truly amazing thing is that two of the best organic fertilizers are easily available to most of us absolutely free. If you’re not careful, you could pay five, 10 or 4,000 times more than necessary to get the nitrogen and other nutrients you need. Garden expert Barbara Pleasant and Mother Earth News editor-in-chief Cheryl Long explain the best ways to use organic fertilizers (some of them free!) to build your best garden soil and grow the happiest, most productive garden plants.

The Best Free Fertilizers

All products labeled “fertilizer” must display their content of the three major plant nutrients: nitrogen, phosphorous and potassium (N-P-K). Most organic fertilizers are bulkier than synthetic chemical products, so their N-P-K percentages are typically lower and their application rates are higher.

Also, because organic products are biologically active, their N-P-K numbers may change somewhat from batch to batch and over time. This can make it hard for producers to comply with the labeling laws. As a result, some excellent organic fertilizer options, such as compost, often are not even labeled as a “fertilizer.” One of the best free fertilizers, grass clippings, breaks down so quickly it can’t be bagged and sold.

But make no mistake, compost and grass clippings do what fertilizers are supposed to do: They enrich garden soil with nutrients that plants and microscopic soil life-forms are eager to use. In most areas, you can easily collect grass clippings from your neighborhood, bagged and ready to bring home—to make sure you’re not collecting clippings treated with chemicals, chat with your neighbors about their lawns. Many communities make yard-waste compost (made mainly from grass clippings and leaves) available for free or a small fee. Contact your city’s waste management department to ask if they offer this service.

If you can get free clippings or compost, how much should you use? We prepared these guidelines with help from soil scientists at Woods End Laboratories in Maine.

Grass Clippings: Grass clippings are one of the best organic fertilizers, and it’s easy to find free local sources. You can mix clippings directly into your garden soil; or apply them as a surface mulch where they will do double duty as a combo fertilizer-mulch, helping to prevent weeds and conserve soil moisture. The nitrogen content of clippings will vary, with fresh grass collected in spring from fertilized lawns topping five percent nitrogen, while clippings from later in the year or from unfertilized lawns will likely contain around two percent nitrogen. Again, be sure to avoid clippings from those “perfect” lawns that have been treated with herbicides.

In most regions, plants can get all the nutrients they need for a full season of growth with these application rates, applied in spring: If mixing into garden soil, apply a 1⁄2-inch layer of fresh clippings (that’s about six 5-gallon buckets per 100 square feet); if using as a surface mulch, apply a 1- to 2-inch layer.

6/18/2015 12:51:53 PM

Good afternoon Ladies, I recently stopped using weed killer on our lawn, when will I be able to, safely, use my grass clippings. Am I looking at 1 or more years? Thank you, Violet

5/28/2015 10:05:22 AM

I make a fertilizer tea of comfrey leaves. I strip the leaves of the comfrey plant and place in a 5 gallon bucket of water. After a few weeks I have a smelly gooey pail of fertilizer tea. I use a cup of the stuff into a 5 gallon pail of fresh water and I fertilize my garden plants with that. It is better than anything I have ever purchased. The stems of the comfrey plant hold medicinal value and I harvest and make comfrey infused oils for the skin. The plant loves it's regular pruning and it quite beautiful in it's own right and is covered with honey bees and bumblebees visiting the pretty purple flowers.



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