Manures
Definition; Manures are plant and animal wastes used as sources of plant nutrients, especially organic in nature, improving soil fertility and structure.
Earlier, chemical substances were also termed manures, but now:
- Organics → Manures
- Inorganics → Fertilizers
Advantages of Manures
- Supply major & micro-nutrients
- Improve soil structure, water-holding capacity
- Enhance nutrient availability
- CO₂ released acts as a fertilizer
- Support soil microbes
- Suppress plant pathogens (e.g., nematodes, fungi)
- Buffering effect in soil pH
- Prevent leaching & erosion losses
Classification Based on Nutrient Concentration
(A) Bulky Organic Manures – Low nutrient content, applied in large quantities
- Examples: FYM, Compost, Green manure
- Farm Yard Manure (FYM)
- Composition: 0.5% N, 0.2% P₂O₅, 0.5% K₂O
- Urine (1% N, 1.35% K₂O) → prone to volatilization loss
- Pit Size: 6–7.5 m × 1.5–2.0 m × 1 m
- Ready after: 4–5 months
- Preservatives: Gypsum, Superphosphate
- Bacteria & Actinomycetes aid decomposition
- Moisture: 60–70% (initial), 30–40% (ready)
- Application: 10–20 t/ha (well-decomposed), 15 days before sowing
- Availability to 1st crop: 30% N, 60–70% P₂O₅, 70% K₂O
- Hot manure: Horse, sheep
- Cold manure: Cattle, pig
- Fire fanging: Ashy fungal growth on moist manure
- Short manure: Fully decomposed
- Long manure: Partially decomposed
- Compost
- Prepared from vegetable & animal waste (not dung)
- Farm compost: 0.5% N, 0.15% P₂O₅, 0.5% K₂O
- Bangalore method compost: 0.8–1.24% N, 0.4–0.59% P₂O₅, 2–3.3% K₂O
- Town compost: 1.4% N, 1% P₂O₅, 1.4% K₂O
- Super compost: Enriched with superphosphate
- Azo compost: Enriched with Azotobacter (1.5% N)
- Night Soil / Poudrette
- Night Soil: 5.5% N, 4% P₂O₅, 2% K₂O
- Poudrette: 1.32% N, 2.8% P₂O₅, 4.1% K₂O
- Made by mixing night soil with ash/soil/charcoal
- Sewage & Sludge
- Sludge (solid) after fermentation → Activated sludge: 3–6% N, 2% P₂O₅, 1% K₂O
- Aeration reduces pathogens, bad odor
- Sewage sickness: due to colloidal clogging and anaerobic bacteria
- Sheep & Goat Manure; 3% N, 1% P₂O₅, 2% K₂O. Penning or shed sweepings used in fields
- Poultry Manure; 3.03% N, 2.63% P₂O₅, 1.4% K₂O. Litter (sawdust, leaves, straw) absorbs waste
- Green Manure
- Green plant material incorporated into soil
- Two types:
- Green manuring: Crop grown & ploughed in-situ
- Green leaf manuring: Collected leaves/twigs applied
- Important plants:
- Sesbania rostrata (stem nodulation): 100–285 kg N/ha in 45–55 days
- Sunnhemp, Dhaincha, Berseem, Glyricidia, Subabul, Pongamia
- Incorporate at flowering stage (low C:N ratio)
- Superphosphate application @ 100 kg/ha enhances P content
- Average N contribution: 60–80 kg N/ha
(B) Concentrated Organic Manures – High nutrient content
Manure Type | N (%) | P₂O₅ (%) | K₂O (%) | Notes |
Bird Guano | 7–8 | 11–14 | 2–3 | Excreta + remains |
Fish Guano | 7 | 8 | – | From oil factories |
Fish Manure | 4–10 | 3–9 | 0.3–1.5 | – |
Raw Bone Meal | 3–4 | 20–25 | – | Slow-release P |
Steamed Bone Meal | 1–2 | 25–30 | – | Better than raw |
Blood Meal | 13–20 | – | – | Rich in Iron, for foliage |
Meat Meal / Tankage | 8–9 | 7 | – | – |
Calcined Bone | – | 37 | – | – |
Oilcakes: | – | |||
Sunflower Cake | 7.8 | – | – | – |
Groundnut Cake | 7.2 | – | – | – |
Cotton Cake | 6.5 | – | – | – |
- Edible cakes: Used as cattle feed
- Non-edible cakes: Used in horticulture
- Mineralization time: 7–10 days
- Neem cake: Acts as nitrification inhibitor
Quick Revision Points for Exam
- FYM: Most used, 10–20 t/ha, 30% N availability
- Poudrette: From night soil, 4.1% K₂O
- Activated Sludge: 3–6% N
- Sunnhemp: Most widely used green manure
- Sesbania rostrata: Stem nodulating, up to 285 kg N/ha
- Blood Meal: Richest in N (13–20%)
- Calcined Bone: Highest in P₂O₅ (37%)
- Azo compost: Cheapest source of N (1.5%)
- Oilcakes: Powdered before use; neem cake reduces nitrification
