Alternatives to Nitrogen Fertilizers

Legumes are an organic alternative to nitrogen fertilizers.Flohsamen, hell und dunkel image by bbroianigo from Fotolia.com

Many farmers and homeowners use nitrogen fertilizers to produce green, lush grass or healthy crops. Producing nitrogen fertilizers requires a lot of energy, however, and consumers often search for environmentally sound and low-cost alternatives. According to the University of California, in 1983 and 1984, it took the equivalent of approximately 32 billion gallons of fuel to produce 74.5 million short tons, worldwide, of nitrogen. But other alternatives, requiring less fuel to produce, are available.

Manure and Sewage Sludge

Beef manure and sewage sludge are organic wastes that can serve as alternatives to nitrogen fertilizers. These options require less fuel energy to produce than nitrogen fertilizers. For example, according to the University of California's Sustainable Agriculture Research and Education Program, it would take 29,899 BTUs to produce 1 lb. of nitrogen fertilizer, but it would only take 1,300 BTUs to produce 1 ton of nutrients found in beef manure (which contains 4.4 percent nitrogen) or sewage sludge (4.0 percent nitrogen).

Crop residues and municipal refuse are also organic waste alternatives to nitrogen fertilizer. Like manure and sewage, this waste is much more energy efficient to replace than nitrogen fertilizer. Table 1 in the reference link shows that crop residues and municipal refuse require less than half (only 500 BTUs/ton) the energy to replace the same amount of nutrients found in an equal amount of manure or sewage. Crop residues and municipal refuse energy requirements (less than 0.01 gallons of diesel fuel per pound) are only a fraction of what it would actually take to produce an equivalent amount of nitrogen fertilizer, which requires 29,899 BTUs per pound (0.240 gallons of diesel fuel per pound).

Legumes are an additional organic alternative source of nitrogen fertilizer, but legumes must go through a biological process in order to become a nitrogen fertilizer source, and that process requires energy to complete. In fact, it requires more than four times the energy needed to make chemical nitrogen fertilizer.

However, gas fuel sources (like diesel) aren't used to produce legume-generated nitrogen fertilizer. Instead, the sun provides the needed energy for this biological process. Sunlight enables legumes to produce approximately 88 million tons of nitrogen for agricultural purposes annually. In comparison, only 55 million tons of chemical nitrogen are generally produced each year.

The organic alternatives to nitrogen fertilizer--like manure, sewage, crop residues and municipal refuse (waste)--don't just require less energy to replace, and they don't just cost less fuel-wise either; these organic alternative sources for nitrogen also, according to the University of California, have a positive affect on soil structure.