Common Components of Organic Fertilizer
• Bone meal—slow release fertilizer high in phosphorus and calcium
• Bat guano—contains all three major macronutrients (proteins, fats & carbohydrates)
• Poultry humus—waste products from the chicken industry contain all three macronutrients and are used locally in Maryland
• Fish emulsion—high in nitrogen, phosphorus, and trace elements
• Fish meal—traditionally used as fertilizer prior to advent of synthetic sources, provides high nitrogen and phosphorus
• Cotton seed meal—high in nitrogen
• Seaweed (kelp) meal—high in micronutrients
Advantages of Organic Fertilizer
• Made from naturally occurring sources, therefore limited amounts of fossil fuels are used in production, potentially lowering the amount of greenhouse gas that is released into the atmosphere.
• Nutrients are released only when media is warm and moist, coinciding with times of greatest need in lawn care and agriculture (although this may not be an issue for greenhouse/ nursery plants, which are always kept under optimum growing conditions). The slow-release nature of most organic fertilizers may slightly decrease the runoff of nutrients into local water systems when compared to some quick-release synthetic sources that release nutrients regardless of media conditions. It is important to note that slow-release synthetic sources may offer similar benefits.
• In terms of the end product, such as the quality of plant produced by a commercial greenhouse, organic fertilizers can be quite competitive with traditional synthetic sources (see http://environmentalhorticulture.umd.edu for a detailed study comparing products of organic and inorganic fertilizers).
• When used over a long period of time during in-ground production, organic fertilizers may increase the quality of the soil, improving the soil structure, or tilth, increasing its ability to hold both water and nutrients, and increasing the efficiency of nutrient utilization, whereas inorganic fertilizers have three main disadvantages:
- They are subject to leaching, which occurs when the fertilizers are washed by rain or irrigation water down below the level of the plant roots. Nitrogen is particularly susceptible to leaching.
- Heavy application of chemical fertilizers can "burn" seedlings and young plants. This is actually a process of drying out, or desiccation, due to the presence of chemical salts within the commercial fertilizers.
- Overly heavy applications can build up toxic concentrations of salts in the soil and create chemical imbalances.
Disadvantages of Organic Fertilizer
• Generally costs significantly more than synthetic fertilizer.
• Organic certification requires documentation and regular inspections.
• Organic fertilizers, despite the advantages discussed above, still release nutrients into their surroundings; these nutrients can find their way into local streams, rivers, and estuaries just as nutrients from synthetic sources do.
Motivations for using organic fertilizer vary from user to user—businesses may want to go organic in order to sell product, and members of the general public might be interested in organic fertilizer for home use because of environmental concerns. Whatever the motivation, and whatever the fertilizer source, proper fertilization procedures will save money and benefit the environment. Soil testing prior to fertilizer application identifies nutrient needs and prevents excess fertilizer from being applied. This prevents waste of money and excess runoff into local waterways. Fertilizer should be applied at the right time; for lawn use, fertilization in early fall is generally recommended. Finally, use common sense to prevent waste; do not fertilize if a heavy rain is forecast!
Thanks to the Home Composting Made Easy, University of Maryland Extension Service, & Steve the Gardenguy.