It has come to my attention since becoming the agricultural extension agent for Columbia County that many home gardeners and small-scale producers have a growing interest in organic gardening. Defining what “organic” means can vary from one person to the next, but generally the intent is to avoid using synthetic or man-made inputs, such as pesticides or conventional fertilizers. On a larger scale, growing organically is defined by the terms of the USDA’s National Organic Program. It tasks an outside organization, the Organic Materials Review Institute (OMRI), with deciding which products are available to organic gardeners and producers.
If you decide to garden by organic standards, it doesn’t mean that you are confined to only animal manure for your fertilizer options. All organic-certified fertilizer products are listed on the OMRI website, www.omri.org. Here you will see there are a multitude of organic fertilizers available for home use.
It is helpful to understand that organic fertilizers differ in several ways from conventional fertilizers. Most organic fertilizers have lower concentrations of essential elements. The three main essential elements are listed on fertilizer labels as 3 numbers, which are percentages of (N)Nitrogen-(P)Phosphate-(K)Potash. An example of this would be to compare a conventional fertilizer like ammonium nitrate which is 30-percent (N)nitrogen, but the organic fertilizer blood meal or feather meal will only have around 12-percent (N)nitrogen. Most organic fertilizers also have slower release rates than conventional fertilizers. Nitrate fertilizers contain nitrogen that is immediately available for plant uptake, and ammonium fertilizers only take 1 to 6 weeks to break down enough for absorption. Many organic fertilizers take from 1 month to as much as 2 years for the nutrients to become plant-available.
Organic fertilizers are often more expensive per unit of nutrient. A recent research project conducted by Dr. Matthew Chappell with the University of Georgia’s Horticulture Department was shared with Extension Agents on price comparisons for several organic fertilizer products versus three conventional fertilizer products. During this research project, all products were tested for longevity and reapplied when needed. Factors in this project are as listed: First fertilization on March 1, final fertilization on August 15, irrigation twice per week until leaching, total of 24 weeks for “fertilizing window”, clay soil growing media, and a cost of $60 for an applicator to make the treatment (This figure is based on fuel, vehicle wear, vehicle cost, labor, and equipment cost to apply treatment). Organic products used were Bio-tone, Garden-tone, Holly-tone, Plant-tone, Flower-tone, Rose-tone, and Bat guano. The non-organic products used were Milorganite, Conventional(10-10-10), and Harrell’s CRF.
So what were the real costs?
Bio-tone/Holly-tone/Rose-tone: 3 applications were made at $82.50 per application plus $60 per treatment. Total of $427.50
Garden-tone: 4 applications were made at $147 per application plus $60 per treatment. Total of $828.
Plant-tone: 4 applications were made at $88.00 per application plus $60 per treatment. Total of $592.
Flower-tone: 4 applications were made at $145.00 per application plus $60 per treatment. Total of $820.
Bat guano: 6 applications were made at $2,100.00 per application plus $60 per treatment. Total of $12,960.
Milorganite: 3 applications were made at $18.00 per application plus $60 per treatment. Total of $234.
Conventional(10-10-10): 2 applications were made at $12.00 per application plus $60 per treatment. Total of $144.
Harrell’s CRF: 2 applications were made at $22.00 per application plus $60 per treatment. Total of $164.