Boost Crop Nutrition Using Smart Manure Management

By Blake Jackson

Manure is a key source of nitrogen (N), phosphorus, potassium, and organic matter, along with various secondary and micronutrients, according to Charles White, Professor of Soil Fertility at Penn State Extension.

However, the ammonium-N fraction in manure is prone to volatilization if not incorporated into the soil quickly after application. This loss not only reduces the nitrogen value of manure, increasing the need for commercial fertilizers, but also contributes to odor and air pollution.

Low-disturbance manure injection is an effective method for conserving ammonium N because it incorporates the manure immediately while maintaining soil structure and residue cover. This approach limits soil erosion compared to traditional tillage-based incorporation.

The available N in manure can be calculated by multiplying the ammonium N content by an availability factor based on incorporation timing and adding it to the organic N content multiplied by its availability factor:

Manure Available N = (Ammonium N × Ammonium N Availability Factor) + (Organic N × Organic N Availability Factor)

This calculation provides available N per 1,000 gallons of liquid manure or per ton of solid manure. Multiplying by the application rate determines the total N applied or can guide the application rate needed to meet target N levels.

Research shows immediate incorporation increases the value of manure N. For example, swine manure at 7,000 gal/ac increases in value by $98/acre, dairy manure by $69/acre, and poultry litter by $18/acre due to the higher ammonium N content in swine manure.

Given current record-high commercial N fertilizer prices, immediate incorporation has never been more economically advantageous.

Low-disturbance injection systems, including dragline or tanker-mounted toolbars, provide cost-effective application while reducing soluble phosphorus losses and air pollution.

Recommendations to Maximize Manure Nitrogen:

• Use low-disturbance injection for liquid manure to maximize N value.
• Apply manure promptly after analysis to conserve ammonium N.
• Consider the ammonium-to-organic N ratio when planning manure use.
• For solid manures, prioritize timing and landscape placement to limit runoff.
• Monitor N fertilizer prices to evaluate the economic benefit of manure injection.

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