Dan Wheat/AP
Jose Jimmez drives a tractor slowly towing a mechanical compost turner that waters and
churns a rotting pile of tree fruit, wood chips and horse manure that will become organic
fertilizer for the Kyle Mathison Orchards, in Wenatchee, Wash.

Manure Makes a Comeback

September 12, 2008 08:54 AM
by Isabel Cowles
As the cost of synthetic fertilizer continues to rise, many U.S. farmers are finding manure an increasingly cost-effective source of crop nutrients.

Synthetic vs. Natural Fertilizers

Since the development of the Haber-Bosch process (the basis for all synthetic nitrogen fertilizers) in the early 20th century, farmers have turned away from manure as a fertilizer.

Today, with synthetic fertilizer costing nearly $1,000 per ton, manure is again becoming a cost-effective way of putting nitrogen and other nutrients back into the soil.

According to livestock environment associate specialist Tommy Bass, a ton of manure contains between $30 to $40 dollars’ worth of nutrients, although not all will be available to the soil in the first year.

In addition to nitrogen, manure provides a wide range of nutrients, including phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper and zinc.

Manure was replaced by synthetic fertilizer in part because it is difficult to transport and can be costly to spread. Moreover, not all manure has the same nutrient content. According to professors at the University of Michigan and Purdue University, “Efficient use of manure as a fertilizer is complicated by the imbalance of nutrients in manure, variability in many sources of manure, difficulties in estimating nutrient availability, and the relatively low nutrient concentration limiting the distances manure can profitably be transported.”
Despite these disadvantages, farmers, environmentalists, academics and government officials are working together to find new ways of effectively reusing this natural waste. For example, in 2005, agricultural, environmental and political leaders in the Shenandoah Valley were working together to encourage new technologies to store and process poultry and other farm animal manure as well as efforts to effectively transport manure to areas where it was needed.

Related Topic: Other uses, sources of waste


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