All fertilizers supply plants with the nutrients your garden needs to be in tip-top shape. However, organic and inorganic fertilizers supply nutrients to soil in different ways. Organic fertilizers create a healthy environment for the soil over a long period of time, while inorganic fertilizers work much more quickly, but fail to create a sustainable environment. Choose the one that best fits your needs, or consider combining them to get the best of both options.
What are Organic and Inorganic Fertilizers?
Organic fertilizers are composed of natural ingredients from plants or animals. Examples include manure and plant parts such as leaves and peanut hulls. Compost, a blend of plant debris broken down by natural processes, is also considered a natural or organic fertilizer. Inorganic fertilizers, on the other hand, are manufactured from minerals or synthetic chemicals. Both organic and inorganic fertilizers supplement the soil and feed plants with nutrients. Macronutrients -- those nutrients that plants require in large amounts -- include nitrogen, phosphorus and potassium and are listed as percentages on the fertilizer bag.
Pros and Cons
There are benefits and what some may consider disadvantages of organic and inorganic fertilizers. Deciding which kind to use may depend on your horticultural situation. According to North Carolina State University, organic matter in natural fertilizers promotes an environment conducive for earthworms and increases the capacity for holding water and nutrients. Organic fertilizers release nutrients slowly, relying on soil organisms to break down organic matter. A slow-release scenario decreases the risk of nutrient leaching but takes time to supply nutrients to plants. Inorganic fertilizers contain a higher percentage of nutrients and provide them more quickly than organic fertilizers. This is a benefit for plants with a short life span, such as bedding plants, but the concentrated form increases the risk of burning the plant if applied incorrectly, and the quick-release of nutrients may result in soil leaching.
Research comparing organic and inorganic fertilizers provides compelling evidence that organic fertilizers bolster soil health over the long term. In a study conducted in Sweden over 32 years, scientists Artur Granstedt and Lars Kjellenberg reported on the differences in soil structure and crop quality between an organic and inorganic system. They found that soil in the organic system had higher fertility, and organic crops had higher yields and starch content than the inorganic system. In contrast, long-term use of synthetic fertilizers depletes soil organisms of the organic matter they need, states the Maine Organic Farmers and Gardeners Association. Eventually, these organisms disappear in soils dependent on inorganic fertilizers.
It does not have to be either organic or inorganic fertilizer. An integrated approach blends the use of both. A study published in 2009 described the benefits of an integrated system on rice fields in India. The authors found that a combination of organic and synthetic fertilizers resulted in yields that increased over five years. They concluded that an integrated approach improved the capacity of the soil to supply nutrients. A blend of both organic and inorganic fertilizers may suit your landscape.
- North Carolina State University: Organic Fertilizers
- Maine Organic Farmers and Gardeners Association: Basics of Organic Soil Fertility
- "Proceedings of an International Conference in Boston, Tufts University, Agricultural Production and Nutrition, Massachusetts; Long-Term Field Experiment in Sweden: Effects of Organic and Inorganic Fertilizers on Soil Fertility and Crop Quality"; Artur Granstedt and Lars Kjellenberg; March 19-21, 1997
- "The Proceedings of the International Plant Nutrition Colloquium XVI ..."; Kuruvilla Varughese, et al.; 2009
- Chicago Botanic Garden: Keep Growing: The Ten-Year Strategic Plan
First published in 2001, Marie Lenahan writes about horticulture, food and green living. Her work has appeared in gardening magazines and academic journals. Lenahan holds a Ph.D. in horticultural science.