Fertilizer has become a word with, well, dirty associations due to the widespread use of chemically synthesized, inorganic fertilizers. These and organic fertilizers made from plant and animal matter have the same chemical components, but there’s a big difference in how they are made, how long they take to release nutrients and their effects on the soil and environment.
Inorganic fertilizers are made via chemical processes that produce ammonia as an end product; this is combined with other compounds including phosphate, potash and urea. The fertilizers produced are concentrated and can be used almost immediately after being mixed with water. They have been linked to a number of environmental problems including water pollution, the acidification of the soil and over-dependency on fertilizer. Producing them also consumes large quantities of natural gas.
In contrast, organic fertilizers are made from compost, manure, seaweed, worm castings and other naturally occurring materials. They produce less predictable results than inorganic ones, but also contribute to biodiversity and the long-term productivity of the soil.
Farmers have, of course, sought for centuries to increase soil fertility using manure and other organic substances. The ancient Roman poet Virgil devotes an entire section of the second book of his Georgics, a long poem about agriculture, to discussing how to identify which types are most fertile.
For your own garden, the choice of organic fertilizer is too clear. Here are some kinds to consider:
1) Bat guano (pdf) promotes the growth of large blooms and fruits and of root growth in seeds and transplants. It’s harvested from bat caves and sold in powdered form.
3) Kelp meal, which — along with kelp powder and liquid kelp — is harvested from the ocean, contains minerals and amino acids, as well as trace amounts of other micronutrients. It can be used on your lawn, in vegetable and flower gardens and in potting mixes.
4) Fish waste can be dried and ground into a powder or made into an emulsion. Heat and acid are used to process nutrients in the latter; enzymes can also be used to break down the fish waste into its components.
5) Biochar is a charcoal produced after waste biomass from woody products from lumber mills, corn, sugarcane and other sources is burned at slow and low heat. This process is called pyrolysis, which, according to Cornell University, provides a “unique alternative energy source because it produces heat and power … while creating biochar with its rich sequestering properties.”
That is, biochar is not only an organic fertilizer. While there are hazards to producing it (due to the burning process), biochar captures carbon dioxide and prevents it from being released into the atmosphere. Cornell Crop and Soil scientist Johannes Lehmann estimates that converting residues from commercial forestry, fallow farm fields, and annual crops through pyrolysis could actually compensate for up to a third of the fossil-fuel emissions produced by the U.S.
Biochar is dusty and turns anything that it comes into contact with black. It can be can be purchased (from Re:char, which makes biochar mixed with compost and coconut coir) or you can even produce your own.
Here’s to digging in the dirt and growing a non-toxic garden!
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