Adding fertilizer to garden soil is essential to replenish the 16 nutrients required to promote and sustain plant life. Growing plants feed on these elements, such as nitrogen, phosphorus, calcium and sulfur, throughout their development, and over time, the nutrient levels would be depleted if fertilizer were not applied. Natural or organic fertilizers like livestock manures, bone meal and vermicompost provide soil with these necessary nutrients and offer gardeners several advantages over traditional fertilizers.
1. Improved Soil Fertility
Besides simply adding nutrients to soil, natural or organic fertilizers also improve the quality and structure of the soil, which over the long term offers additional advantages like improved water retention and drainage. Unlike synthetic fertilizers, natural fertilizers like manures and wood ash also add organic matter and humus to the soil, which provide a constant and balanced supply of nutrients and improve root growth. In addition, organic fertilizers feed and sustain beneficial microorganisms that live in the soil, which chemical products often destroy by increasing acid levels in soil.
2. Less Processing Needed
Synthetic fertilizers require more processing than naturally derived organic fertilizers and are dependent on nonrenewable resources like petroleum, coal and natural gas. On the other hand, organic fertilizers are byproducts of animal and plant materials or mined from rock minerals. For example, plant-based fertilizers include corn gluten, alfalfa meal and seaweed, and common animal-based natural fertilizers include bone meal, fish emulsion, worm castings and animal manures. Natural fertilizers like poultry manure can be sourced directly from farms, while others like bone meal are purchased commercially. To ensure a product is natural, buy those with labels marked “natural organic” and “low analysis.”
3. Less Risk of Plant Injury
Because synthetic fertilizers provide high concentrations of nutrients to the soil, they can potentially injure young plants by damaging or burning their roots. Organic fertilizers, however, must first be broken down by soil microbes before their nutrients can be absorbed by plants. As a result of this slow process, the risk of overfeeding and burning plant roots when using a natural fertilizer is reduced. Of natural fertilizers, only fresh manures carry this burn risk, which is eliminated by first composting the manure before applying to soil.
4. Environmental Advantages
The slow-release nature of organic fertilizers also offers environmental advantages. For example, chemical fertilizers are water-soluble, which allows any excess unused fertilizer to be washed away by rain or heavy watering and eventually enter groundwater and pollute streams and lakes. Conversely, natural fertilizers improve moisture retention in the soil, making leaching less likely. In addition, ingredients in organic fertilizers are naturally biodegradable.
Although both synthetic and organic fertilizers may carry safety risks and must be used with care, ingesting chemical fertilizers can be especially harmful to children and pets. Therefore, when used as directed, organic fertilizers are a safer alternative. To minimize risk and to ensure the correct amount and balance of fertilizer is applied, have soil nutrient levels tested.
- National Gardening Association: Using Organic Fertilizers
- Sustainability Council Newsletter: Two Big Benefits of Using Organic Fertilizers
- Oregon State University Extension Service: Here's the Scoop on Chemical and Organic Fertilizers
- Colorado State University Extension: Organic Vs. Manufactured Fertilizers
- Organic Gardening: Organic Fertilizers
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