Manures

Manures are mixtures of animal excreta, urine, and bedding materials collected from livestock and poultry operations and used as fertilizer or soil conditioner. They can be applied directly in raw form or after processing such as composting, aging, drying, or digestion. Common sources include cattle, horse, sheep, and goat manures; poultry litter; swine slurry; and digested effluent from biogas plants. The nutrient content of manures varies by source and management, but they generally supply nitrogen, phosphorus, potassium, and micronutrients, along with organic matter that improves soil structure. The rate and timing of application depend on crop needs, soil properties, and local regulations; improper use can lead to nutrient losses through volatilization, leaching, or runoff.

Processing options include composted manure, which is more stable and has reduced odors, pathogens, and weed seeds; anaerobically digested manure yields biogas and a more uniform digestate; and dried or pelletized forms that are easier to transport and handle.

Benefits and risks: manure can improve soil organic matter, water-holding capacity, microbial activity, and nutrient supply; risks include odor, disease transmission concerns, nutrient pollution, and potential accumulation of contaminants in some cases. Environmental management practices address storage, handling, and application to minimize emissions and water contamination, and many regions regulate timing, rates, and setbacks. Manures remain an important resource in sustainable farming, often used alongside other organic amendments.