Sustainable and Organic Fertilizer
The use of organic fertilizer in sustainable gardens and farms is quickly gaining in popularity - the number of acres of organic agriculture increased from 59 million in 2004 to nearly 81 million in 200975 - especially as their mitigating effects on the environment are demonstrated through more and more studies. While the use of synthetics amendments is both dangerous and expensive, not all organic amendments can be considered sustainable.
The best fertilizer is the gardener's shadow. - Unknown
Chemical Fertilizer vs Organic Fertilizer
Nitrogen fertilizers break down into nitrates upon application. Nitrates are necessary for the plants growth but an excess will leach into groundwater supplies and can contaminate sources miles away. Because nitrogen leaches through the soil more quickly, over-application is abundant. These chemical fertilizers have a hugely negative effect on plant and aquatic life, as well as human health.76
Numerous studies have shown the negative effects chemical fertilizers have on our environment and health. One study from Stanford University77 is a great example of the difference between the use of chemical and organic fertilizers.
According to its findings, soil fertilized with organic fertilizer contained naturally occurring microbes that turned any excess nitrogen into a benign gas, dinitrogen. These microbes are found less frequently and were less active in soil fertilized with chemicals. The more leaching of nitrogen, the greater application is applied, the fewer microbes and the more poisoning of land and water.
And when comparing chemical fertilizers vs organic fertilizers it's important to mention one study from the University of California, Berkeley75 that states sustainable farming can indeed "feed the world", despite what proponents and manufacturers of chemical fertilizers would have us believe. It produces as high harvest rates, using less inputs and virtually eliminates the pollution or contamination that leads to health and environmental issues.
Most Sustainable Organic Fertilizer
There are many kinds of organic fertilizer and the options can be overwhelming. But as mentioned before, organic doesn't always mean sustainable. The best tip to keep in mind for home gardening is to avoid purchasing your amendments from the store. Purchasing a garden amendment still contributes to waste, instead of eliminating it. Alternatively, creating a closed-cycle within your home or community accomplishes two tasks at once.
- Compost: You really can't get enough of this. Made from your own yard and kitchen scraps, compost creates a fully closed-cycled system within your home. Little is wasted and its benefits are unsurpassed as both a soil amendment and mulch. Compost in greater amounts can also be acquired from local farmers or for free from communities with a composting program.
It contains a lower nitrogen level, so use it in conjunction with the techniques below. It can be applied as frequently and as thickly as you'd like or feel you need, but twice a year (spring and fall) and one inch thick is generally preferred. Read more about home composting here.
- Grass clippings: They decompose quickly and provide the soil with nitrogen and other nutrients (between 2-5% depending on the season). They also diminish weeds and act as mulch, conserving water. They can be acquired for free from neighbor's lawns but avoid clippings from weedless lawns, as they likely contain herbicides that can damage your soil's microbial activity.
Add approximately a two inch layer of grass clippings in the spring, when the nitrogen levels are at their highest and slightly more in the fall when levels are lower. For fertilizing lawns, simply remove the bag from your mower (or use a push mower) to leave the clippings on the ground.
- Manures: High in nitrogen, animal waste from cows, horses, chickens, or pigs are a great amendment to the soil and give sustainable use to an otherwise smelly by-product. Trust me when I say many animal owners will be more than happy to have you shovel out their pens or corrals, making manures readily available and practically free. Horse manures are used less frequently as they are more likely to contain seeds from alfalfa or hay, which may sprout and take over your yard. However, I've used them without issue and since alfalfa can act as a cover crop, it can be beneficial in small amounts. Keeping your own backyard chickens can even create a closed looped in your garden.
All manures should be aged (at least a week or until dry) to avoid burning of plants or grass. Apply them 1-2 times a year, approximately half an inch thick. Important: Know the source of your manure. Be sure the animal is healthy and raised organically, without hormones or routine antibiotics, and is fed a healthy, natural diet (i.e. cows should be grass-fed, chickens should be free-range).
- Cover crops: Cover crops, such as alfalfa or clover, are planted between regular crop cycles, during dormant periods or around perennial trees or shrubs. Many "fix nitrogen" or other nutrients, meaning they gather important minerals from the air or surrounding earth through their leaves and roots and deposit them in the soil, making them readily available for other plants.
Finding multi-purpose cover crops is ideal. Legumes, such as beans, act as a nitrogen-fixer while also giving you food. Some cover crops can double as organic matter in compost or as mulch. Other, such as clover, will fix nitrogen while attracting beneficial insects, such as bees.
- Mulches: The use of organic mulch is as important as the use of compost. A thin or thick layer (depending on the plant) of wood bark, dried leaves, grass clippings, or any other organic material will primarily help retain moisture, but will also break down over time, acting as a slow release fertilizer and adding to soil fertility. Learn more about mulching here.
- Locally available organic fertilizers: The key is sustainable use of what you have available that otherwise would go to waste. Seaweed, if you live near the ocean; fish heads or animal wastes from hunting or fishing; even dead animals buried deeply can all assist in soil fertility. Be sure any animal products are not from diseased animals, are not buried where fruits or veggies will be planted for at least a year and are buried several feet deep to avoid scavenging animals or pets from digging.
With most other organic fertilizer, avoid mixing amendments in more than a few inches; any deeper can cause a microbial burst of energy and quickly diminish nutrients, as well as stir up weed seeds. Tilling for the home gardener should be done rarely if at all.
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