Overview of Manures
Manures are natural substances obtained by the decomposition of animal wastes and plant residues. They supply organic matter to the soil in large quantities but supply nutrients in small quantities. The process of adding manure to the soil helps enrich the soil with nutrients and organic matter (humus), increasing its fertility.
Types of Manures
- Farm Yard Manure (FYM): Produced from the decomposition of cattle dung, urine, and litter.
- Compost: Prepared by decomposing farm waste like vegetable peels, animal refuse, sewage waste, and weeds in pits.
- Vermicompost: A type of compost prepared by using earthworms (like red wigglers) to hasten the decomposition of plant and animal refuse.
- Green Manure: Fast-growing plants like sunn hemp or guar are grown and then mulched by ploughing them into the soil. They decompose to provide nitrogen and phosphorus.
Advantages of Manures
Using manure is considered a sustainable agricultural practice because it recycles waste and improves long-term soil health.
- Soil Structure: It adds humus to the soil, improving its texture. In sandy soils, it increases water-holding capacity. In clayey soils, it helps in drainage and prevents waterlogging.
- Biological Activity: It provides food for soil organisms, increasing the population of beneficial microbes and earthworms.
- Eco-friendly: It helps in recycling farm waste and reduces environmental pollution compared to chemical fertilizers.
Limitations of Manures
- Low Nutrient Content: They contain nutrients in small amounts, so large quantities are required to meet plant needs.
- Bulkiness: Being bulky, they are inconvenient to store and transport.
- Slow Release: Nutrients are released slowly into the soil, which may not meet the immediate high demand of crops.
Comparison: Manure vs Fertilizer
| Feature | Manure | Fertilizer |
|---|---|---|
| Source | Natural/Organic | Inorganic/Chemical |
| Nutrients | Low concentration | High concentration |
| Soil Humus | Provides humus | Does not provide humus |
| Absorption | Slow | Rapid |
Extra Practice Questions
- Why is green manure specifically grown before sowing the main crop?
- Name two specific nutrients that green manure enriches the soil with.
- How does manure help in sandy soils?
- What is the role of earthworms in vermicomposting?
- Why are manures considered better for the environment than fertilizers?
