16 January 2008

3 minute read

North America

Jon Rausch, Ohio State University Extension environmental management program director, said that more Ohio farmers are turning to manure for corn production because of the higher prices of nitrogen, potassium and phosphorus. However, they face the challenge of proper nutrient utilization to maximize results.

"When manure is treated like a nutrient resource, it can be a cost-effective asset to crop production. To maximize manure's value, it must replace other nutrient inputs and be placed where a crop response is expected," said Rausch. "Adding nutrients above recommended levels would decrease its value and increase the potential of those nutrients being lost to the environment."

Existing nutrient levels in the soil, how much manure is applied, how well manure is spread, and how well soil nutrients are maintained with manure application are just some of the variables that can influence the value of manure as a fertilizer resource.

Rausch and his colleagues conducted studies that demonstrate how the value of manure, specifically from swine, depends upon the need for supplemental nutrients, proper manure handling and thorough application practices.

For example, they found that swine manure applied as a sidedress to corn and injected into the soil could potentially generate nutrient value (nitrogen, potassium, phosphorus) of up to $136 per acre. By contrast, swine manure applied on the soil surface only results in a value of about $80 per acre due to nitrogen losses.

Rausch and his colleagues also found that when potassium and phosphorus have already reached soil saturation levels, the additional potassium and phosphorus from manure would not be utilized, nor would yields increase.

"As a result, farmers are losing the economic value of potassium and phosphorus (to the tune of nearly $58 per acre) and both would be better utilized on acres that need those nutrients," said Rausch. "Ideal conditions of using manure nutrients to their fullest include soil tests that indicate addition of potassium and phosphorus are necessary, an even and uniform process of manure application, and minimizing those nitrogen losses."

Not only does manure add nutrient value to a crop, it also adds environmental benefits, including micronutrients, organics, and biologicals -- those organisms that make up the "living soil." Though difficult to quantify with direct economic value, manure has been shown to improve soil quality and soil health, increase organic matter content and build water-holding capacities, among other benefits, said Rausch.

"When a farmer is looking at 60 cents per pound of commercial nitrogen as fertilizer, using manure not only for the nutrient value, but also for the secondary benefits, might be an alternative to consider," said Rausch.

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