Organic Manures

Organic manures are plant and animal wastes used as sources of plant nutrients. These materials release nutrients after decomposition, enriching soil fertility. They are derived from animal, human, and plant residues in complex organic forms.

Major Sources of Manures

1. Cattle Shed Wastes: Dung, urine, slurry from biogas plants
2. Human Habitation Wastes: Night soil, human urine, town refuse, sewage, sludge
3. Animal Wastes: Poultry litter, droppings of sheep and goat
4. Slaughterhouse Wastes: Bone meal, meat meal, blood meal, horn and hoof meal, fish wastes
5. Agro-Industry Byproducts: Oil cakes, bagasse, press mud, fruit and vegetable processing wastes
6. Crop Wastes: Sugarcane trash, stubbles, and related materials
7. Other Sources: Water hyacinth, weeds, tank silt, green manure crops, green leaf manuring materials

Types of Organic Manures

Organic manures can be classified into two main categories:

1. Bulky Organic Manures

These manures contain a small percentage of nutrients and must be applied in large quantities. The most widely used bulky organic manures are farmyard manure (FYM), compost, and green manure.

Advantages of Bulky Organic Manures

• Supply plant nutrients, including micronutrients
• Improve soil structure and water-holding capacity
• Increase the availability of nutrients
• Release carbon dioxide during decomposition, which acts as a CO₂ fertilizer
• Control plant parasitic nematodes and fungi by altering the microbial balance in soil

Types of Bulky Organic Manures

a) Farmyard Manure (FYM)

• Composed of decomposed dung, urine of farm animals, and leftover fodder
• Nutrient content: 0.5% N, 0.2% P₂O₅, 0.5% K₂O
• Application rate: 10–20 t/ha (higher for fodder crops, vegetables, and orchard crops)
• Crops responding well to FYM: Potato, tomato, carrot, onion, sugarcane, rice, and orchard crops

b) Vermicompost

• Formed from earthworm excreta, rich in humus and nutrients
• Enhances plant growth, improves soil texture, and increases microbial activity
• Free from pathogens, toxic elements, and weed seeds
• Contains growth hormones like auxins and gibberellins

c) Sheep and Goat Manure

• Higher in nutrients than FYM (N: 3%, P₂O₅: 1%, K₂O: 2%)
• Applied in two ways:
  1. Collected from sheds, decomposed, and later applied
  2. Sheep penning: Sheep/goats are kept overnight in fields, enriching the soil with urine and feces

d) Poultry Manure

• High in nitrogen and phosphorus
• Nutrient content: N: 3.03%, P₂O₅: 2.63%, K₂O: 1.4%
• Loses 50% of nitrogen if exposed for 30 days

e) Green Manuring

• Process of incorporating fresh green plant tissues into the soil to improve fertility
• Adds organic matter and nitrogen to the soil

Types of Green Manuring

• Green Manuring In-Situ
  • Crops grown in the field and plowed into the soil
  • Examples: Sunhemp, Dhaincha, Cowpea, Berseem, Mung bean
• Green Leaf Manuring
  • Collection of green leaves and twigs from trees/shrubs and incorporation into soil
  • Examples: Neem, Mahua, Glyricidia, Pongamia, Sesbania

2. Concentrated Organic Manures

These manures contain a higher percentage of nutrients than bulky organic manures and act as slow-release organic nitrogen fertilizers.

Types of Concentrated Organic Manures

a) Oil Cakes

• Byproducts of oil extraction from seeds
• Classified into edible and non-edible oil cakes

b) Animal-Based Concentrated Organic Manures