Animal manure is rich in organic matter and essential nutrients required for crop growth, making it a valuable resource in agricultural production. Historically, it has been widely recognized that “more manure means more fertility, more fertility leads to richer soil, and richer soil yields more grain.” However, improper application of manure in recent years has led to various agricultural and environmental challenges. To maximize its benefits, manure must be properly processed and utilized. This article explores the composition of different types of animal manure, their advantages and risks, and best practices for converting manure into effective fertilizer.
Composition of Animal Manure
Animal manure primarily consists of cellulose, hemicellulose, lignin, proteins and their breakdown products, fats, organic acids, enzymes, and various inorganic salts. The nutrient content varies depending on the animal source.
1. Pig Manure
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Organic matter: 15%
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Nitrogen (N): 0.5%
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Phosphorus (P): 0.5–0.6%
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Potassium (K): 0.35–0.45%
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Characteristics: Fine texture, high nitrogen content, low carbon-to-nitrogen (C:N) ratio (~14:1), rich in humus, and strong cation exchange capacity (CEC). However, it has high moisture content and fewer cellulose-decomposing microbes.
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Optimization: Mixing with horse manure introduces cellulose-degrading bacteria, enhancing decomposition and fertilizer efficiency.
2. Cattle Manure
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Organic matter: 14.5%
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Nitrogen (N): 0.30–0.45%
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Phosphorus (P): 0.15–0.25%
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Potassium (K): 0.10–0.15%
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Characteristics: Dense texture, slow decomposition, low heat generation (“cold” fertilizer).
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Optimization: Drying and mixing with horse manure improves aeration and decomposition, producing a high-quality organic fertilizer.
3. Horse Manure
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Organic matter: 21%
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Nitrogen (N): 0.4–0.5%
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Phosphorus (P): 0.2–0.3%
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Potassium (K): 0.35–0.45%
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Characteristics: High fiber content, fast moisture evaporation, rich in cellulose-degrading microbes (“hot” fertilizer).
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Optimization: Effective in improving clay soil structure due to its fibrous nature.
4. Sheep Manure
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Organic matter: 24–27%
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Nitrogen (N): 0.7–0.8%
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Phosphorus (P): 0.45–0.6%
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Potassium (K): 0.4–0.5%
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Characteristics: Fine texture, high nutrient concentration, intermediate heat generation (“warm” fertilizer).
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Optimization: Suitable for both sandy and clay soils.
5. Poultry Manure (Chicken, Duck, Goose, Pigeon, etc.)
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Organic matter: 25.5%
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Nitrogen (N): 1.63% (mainly in uric acid form)
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Phosphorus (P): 1.54%
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Potassium (K): 0.85%
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Characteristics: High salinity, rapid decomposition risk, may attract pests. Uric acid can harm plant roots if not properly decomposed.
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Optimization: Requires thorough composting before use to reduce toxicity.
Benefits and Risks of Manure Fertilization
Advantages
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Comprehensive Nutrients: Provides macro- and micronutrients, along with growth-promoting compounds and beneficial microbes.
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Soil Structure Improvement: Enhances soil aggregation, water retention, and aeration through humic substances.
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Temperature Regulation: Different manure types (hot, warm, cold) help moderate soil temperature.
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Microbial Activity Stimulation: Promotes beneficial soil microorganisms that aid nutrient cycling.
Risks
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Salinization: Fresh poultry manure can increase soil salinity, inhibiting seed germination and causing root burn.
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Pathogens & Weed Seeds: Untreated manure may contain harmful bacteria, parasites, and weed seeds.
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Heavy Metals & Antibiotics: Contamination risks from industrial farming practices.
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Nutrient Imbalance: Highly variable nutrient content makes precise application difficult.
Best Practices for Manure Utilization
1. Proper Composting
Raw manure must be fully decomposed to:
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Accelerate nutrient release.
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Kill pathogens, weed seeds, and pest eggs.
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Reduce phytotoxicity (e.g., uric acid in poultry manure).
Methods:
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High-Temperature Fermentation: Utilize solar greenhouse heat (60–70°C) for rapid decomposition.
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Windrow Composting: Natural pile fermentation, enhanced with microbial inoculants (e.g., ETS bacteria) to speed up the process.
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Bioaugmentation: Use specialized microbial consortia to break down organic matter efficiently.
2. Soil-Specific Manure Selection
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Sandy Soils: Apply sticky manures (e.g., pure pig or chicken manure) to improve water and nutrient retention.
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Clay Soils: Use fibrous manures (e.g., sheep/cattle manure mixed with straw) to enhance porosity.
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Saline/Alkaline Soils: Avoid high-salinity poultry manure; prefer well-composted cattle/sheep manure.
3. Deep Plowing After Application
Manure should be incorporated at >30 cm depth to prevent nutrient stratification and root zone toxicity.
4. Integrated Fertilization Strategies
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Combine with Chemical Fertilizers: Ensures balanced nutrient supply while reducing synthetic fertilizer dependency.
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Enhance with Microbial Inoculants: Accelerates decomposition and improves soil microbiome.
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Supplement with Humic Acids/Algae Extracts: Boosts soil health and plant resilience (e.g., “Sea Spirit” formulations).
Conclusion
Transforming manure into high-quality fertilizer requires a scientific approach—composting, tailored application, and integrated nutrient management. By addressing its risks and leveraging its benefits, farmers can sustainably enhance soil fertility, crop yields, and environmental health. As ancient wisdom meets modern agronomy, manure remains a cornerstone of regenerative agriculture.
