Manures: Introduction and Importance
Introduction to Manures
- Manures are organic materials of plant or animal origin that are added to soil to improve soil fertility and soil health. They are obtained from the decomposition of crop residues, animal excreta, and other organic wastes. Manures supply nutrients in small quantities but play a major role in improving the physical, chemical, and biological properties of soil.
- Manures have been used in agriculture since ancient times and form an essential component of Integrated Nutrient Management (INM) and sustainable agriculture. Unlike chemical fertilizers, manures primarily improve soil quality rather than supplying large amounts of nutrients.
Definition
Manures are organic substances derived from plant residues and animal wastes which, when applied to soil, enhance soil fertility by adding organic matter and releasing nutrients slowly.
Examples of Manures
- Farmyard Manure (FYM): Farmyard manure is a mixture of animal dung, urine, litter, and leftover fodder. It is the most commonly used organic manure in India. FYM improves soil structure, water-holding capacity, and microbial activity. It supplies small amounts of N, P, K and improves overall soil fertility. Average Nutrient Composition: Nitrogen (N): 0.5 %. Phosphorus (P₂O₅): 0.2 %. Potassium (K₂O): 0.5 %
- Compost: Compost is prepared by controlled decomposition of crop residues, farm wastes, and organic materials. It is more uniform and stable than raw organic wastes. Compost improves soil organic matter, enhances nutrient availability, and reduces waste accumulation on farms. Average Nutrient Composition: Nitrogen (N): 0.5–1.0 %. Phosphorus (P₂O₅): 0.3–0.6 %. Potassium (K₂O): 0.5–1.0 %
- Green Manure: Green manuring involves growing leguminous crops (such as sunhemp, dhaincha) and incorporating them into soil at the flowering stage. Green manures add organic matter and biologically fixed nitrogen to soil, improve soil structure, and enhance microbial activity.
- Vermicompost: Vermicompost is produced through the action of earthworms on organic wastes. It is rich in plant-available nutrients, beneficial microorganisms, enzymes, and growth-promoting substances. Vermicompost improves soil fertility, crop growth, and nutrient use efficiency. Average Nutrient Composition: Nitrogen (N): 1.5–2.0 %. Phosphorus (P₂O₅): 0.9–1.2 %. Potassium (K₂O): 1.0–1.5 %
- Poultry Manure: Poultry manure consists of droppings of birds mixed with litter materials. It is a nutrient-rich manure, especially high in nitrogen and phosphorus. Poultry manure releases nutrients rapidly and is effective for improving crop yield when properly composted.
- Characteristics of Manures
- Low nutrient concentration compared to fertilizers
- Nutrients released slowly and steadily through decomposition
- Rich source of organic matter
- Improve soil structure and microbial activity
- Environment-friendly and renewable
3. Importance of Manures
i) Improvement of Soil Physical Properties
- Improve soil structure and aggregation, making soil loose and friable.
- Increase porosity and aeration, promoting better root growth.
- Enhance water-holding capacity, especially in sandy soils.
- Reduce soil compaction, crusting, and erosion.
- Improve soil tilth and ease of cultivation.
ii) Improvement of Soil Chemical Properties
- Supply essential nutrients such as N, P, K, S, and micronutrients.
- Increase cation exchange capacity (CEC) for better nutrient retention.
- Buffer soil pH and minimize acidity or alkalinity problems.
- Reduce nutrient fixation and improve nutrient availability.
- Maintain balanced nutrient status in soil.
iii) Improvement of Soil Biological Properties
- Increase soil microbial population and activity.
- Enhance mineralization of organic nutrients.
- Improve soil enzyme activity.
- Encourage beneficial organisms like earthworms, improving soil fertility.
iv) Role in Nutrient Supply
- Provide slow and sustained nutrient release.
- Reduce nutrient losses through leaching and volatilization.
- Improve efficiency of chemical fertilizers when used together.
- Supply secondary and micronutrients often ignored by fertilizers.
v) Role in Sustainable Agriculture
- Maintain long-term soil fertility and productivity.
- Increase soil organic carbon content.
- Recycle farm wastes effectively.
- Reduce dependence on chemical fertilizers.
- Promote eco-friendly and sustainable farming systems.
vi) Environmental and Economic Benefits
- Aid in waste recycling and reduce environmental pollution.
- Minimize soil erosion and runoff losses.
- Improve soil resistance to drought and stress.
Important Points
- Manures are organic materials of plant or animal origin added to soil to improve soil fertility and soil health.
- They are derived from crop residues, animal dung and urine, poultry waste, green plants, and organic farm wastes.
- Manures supply nutrients in low concentrations, but their major contribution is through improvement of soil properties.
- Unlike chemical fertilizers, manures primarily improve soil quality rather than supplying nutrients in large quantities.
- Manures are an essential component of Integrated Nutrient Management (INM) and sustainable agriculture.
- Addition of manures improves soil physical properties such as structure, aggregation, porosity, and water-holding capacity.
- Manures reduce soil compaction, crusting, erosion, and runoff, thereby improving soil tilth.
- Organic matter from manures increases cation exchange capacity (CEC), enhancing nutrient retention.
- Manures help in buffering soil pH, reducing the harmful effects of soil acidity or alkalinity.
- They stimulate soil microbial population and activity, which is vital for nutrient cycling.
- Nutrients from manures are released slowly and steadily through mineralization, ensuring sustained nutrient supply.
- Use of manures reduces nutrient losses by leaching and volatilization and improves fertilizer use efficiency.
- Manures supply secondary nutrients and micronutrients often neglected by chemical fertilizers.
- Continuous use of manures increases soil organic carbon, which is crucial for long-term soil fertility.
- Manures promote eco-friendly agriculture by recycling farm wastes, reducing pollution, and lowering dependence on chemical fertilizers.
