From another article:
"Soil fertility doesn't originate from animals; it comes from plants at the bottom of the food chain. When grass is filtered through a cow most of the nitrogen is lost in her urine. Instead, take the grass that would go to feed a cow and put it directly into your compost pile - you'll get the nitrogen you need in addition to other nutrients that aren't found in manure. Using the grass and other plant-based materials yields more organic matter than manure."
http://biofertilizer.com/biofertilizer/organic_gardening_veg...
If you are growing vegetables though, you can easily just rotate your crops year by year between crops that fix nitrogen into the soil (like peas, beans, clover, grass) and other crops that take nitrogen (like corn, berries, etc).
"Legumes are an example of a nitrogen fixing plant. These should be rotated with your vegetable crop in order to keep a proper amount of nitrogen in your soil. Crops most often paired by farmers are rice and cotton, and soybeans and maize. These crop pairings are essential for the continuing health of the soil."
If you are growing vegetables though, you can easily just rotate your crops year by year between crops that fix nitrogen into the soil (like peas, beans, clover, grass) and other crops that take nitrogen (like corn, berries, etc).
"Legumes are an example of a nitrogen fixing plant. These should be rotated with your vegetable crop in order to keep a proper amount of nitrogen in your soil. Crops most often paired by farmers are rice and cotton, and soybeans and maize. These crop pairings are essential for the continuing health of the soil."
http://www.helpfulgardener.com/organic/2006/crop.html