Manures - Agrobotany

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Manures

Manures are organic materials from plant and animal wastes that serve as sources of plant nutrients. They release nutrients upon decomposition and, although they have lower nutrient content compared to fertilizers, they improve soil physical properties and have a longer residual effect. Major sources of manures include:

• Cattle shed wastes: dung, urine, and biogas slurry
• Human wastes: night soil, urine, town refuse, sewage, sludge
• Poultry litter and droppings from sheep and goats
• Slaughterhouse wastes: bone meal, meat meal, blood meal, horn and hoof meal, fish wastes
• Agro-industry byproducts: oil cakes, bagasse, press mud, fruit and vegetable processing wastes
• Crop wastes: sugarcane trash, stubbles, and related materials
• Water hyacinth, weeds, tank silt
• Green manure crops and green leaf manuring materials

Manures are categorized into bulky organic manures and concentrated organic manures based on nutrient concentration.

Bulky Organic Manures

Bulky organic manures, including farmyard manure (FYM), compost, and green manure, are applied in large quantities due to their low nutrient content. They provide essential plant nutrients, enhance soil structure and water retention, increase nutrient availability, release CO₂ during decomposition, and help control plant pests by altering soil microorganisms.

Farmyard Manure (FYM):

FYM is a decomposed mixture of dung, urine, litter, and leftover fodder from farm animals. Well-decomposed FYM typically contains 0.5% nitrogen (N), 0.2% phosphorus (P₂O₅), and 0.5% potassium (K₂O). It should be applied three to four weeks before sowing if partially rotten or immediately before sowing if well-rotted. Generally, 10 to 20 tons per hectare is recommended, with higher rates for fodder grasses and vegetables, applied at least 15 days in advance to prevent nitrogen immobilization.

Vegetables like potatoes, tomatoes, sweet potatoes, carrots, radishes, and onions benefit significantly from FYM, as do crops like sugarcane, rice, napier grass, oranges, bananas, mangoes, and coconuts. About 30% of nitrogen, 60-70% of phosphorus, and 70% of potassium in FYM are available to the first crop.

Vermicompost

Vermicompost is the nutrient-rich excreta of earthworms, produced by turning organic waste into earthworm castings. These castings are crucial for soil fertility, containing high levels of nitrogen, potassium, phosphorus, calcium, and magnesium. The natural burrowing of earthworms improves soil water permeability.

Materials for Vermicompost:

• Crop residues
• Weed biomass
• Vegetable waste
• Leaf litter
• Hotel refuse
• Agro-industry waste
• Biodegradable urban and rural waste

Advantages of Vermicompost:

• Rich in essential plant nutrients
• Enhances plant growth, new shoots, and quality of produce
• Easy to handle, apply, and store; odor-free
• Improves soil structure, texture, aeration, water retention, and prevents erosion
• Rich in beneficial microflora, enhancing soil environment
• Increases earthworm population and activity
• Prevents nutrient loss and improves fertilizer efficiency
• Free from pathogens, toxic elements, and weed seeds
• Accelerates organic matter decomposition in soil
• Contains valuable vitamins, enzymes, and hormones like auxins and gibberellins

Sheep and Goat Manure

Sheep and goat droppings are richer in nutrients than farmyard manure (FYM) and compost, containing about 3% nitrogen (N), 1% phosphorus (P₂O₅), and 2% potassium (K₂O). They can be applied to fields either by decomposing shed sweepings in pits or through sheep penning, where animals are kept in the field overnight, incorporating urine and fecal matter into the soil using a blade harrow or cultivator.

Poultry Manure

Bird excreta ferments quickly, losing 50% of its nitrogen if left exposed for 30 days. Poultry manure is high in nitrogen and phosphorus, with an average nutrient content of 3.03% nitrogen (N), 2.63% phosphorus (P₂O₅), and 1.4% potassium (K₂O).

Green Manuring

Green manuring involves incorporating green plant tissues into the soil to enhance its physical structure and fertility, particularly by enriching it with nitrogen. This practice can be done by growing green manure crops in the field (green manuring in-situ) or by adding green leaves and tender twigs from plants grown elsewhere (green leaf manuring).

Types of Green Manuring:

• Green Manuring In-Situ: Growing green manure crops such as sunhemp, dhaincha, mung, and cowpea directly in the field and then burying them.
• Green Leaf Manuring: Incorporating green leaves and twigs from plants like glyricidia, wild dhaincha, and neem into the soil.

Characteristics of Good Green Manure:

• Produces a large quantity of green material quickly
• Grows rapidly to suppress weeds
• Is succulent with more leafy growth
• Is often a legume, fixing atmospheric nitrogen
• Has deep, fibrous roots to absorb nutrients from lower soil layers
• Can grow in poor soils

Advantages of Green Manuring:

• Adds organic matter and stimulates soil microorganisms
• Improves soil structure, water-holding capacity, and reduces runoff and erosion
• Transfers nutrients from lower soil layers to the upper layer
• Fixes atmospheric nitrogen
• Increases availability of nutrients like phosphorus, calcium, magnesium, and iron
• Reduces weed growth during the off-season
• Helps reclaim alkaline soils and control root-knot nematodes
• Provides nutrition for soil organisms, enhancing biological activity
• Improves soil aeration and structure
• Maintains or increases soil organic matter content
• Reduces soil compaction and mitigates the impact of rainfall and vehicle traffic

Disadvantages of Green Manuring:

• May deplete soil moisture, affecting the succeeding crop
• Occupies the field for 75-80 days, reducing the time available for other crops
• Can increase pests and diseases if not managed properly
• Requires phosphatic fertilizers to boost growth and nutrient availability

Concentrated Organic Manures

Concentrated organic manures, such as oilcakes, blood meal, and fish manure, have higher nutrient content than bulky organic manures. These manures are also called organic nitrogen fertilizers. Their organic nitrogen is converted into ammoniacal and nitrate nitrogen through bacterial action, making them slow-acting but providing a long-term nitrogen supply.

Types of Oilcakes:

• Edible Oilcakes: Suitable for livestock feed, such as groundnut cake and coconut cake.
• Non-Edible Oilcakes: Not fit for livestock feed, like castor cake, neem cake, and mahua cake.

Average Nutrient Content of Oil Cakes

Oil-cakes	Nutrient content (%)
	N	P2O5	K2O
Non edible oil-cakes
Castor cake	4.3	1.8	1.3
Cotton seed cake (undecorticated)	3.9	1.8	1.6
Karanj cake	3.9	0.9	1.2
Mahua cake	2.5	0.8	1.2
Safflower cake (undecorticated)	4.9	1.4	1.2
Edible oil-cakes
Coconut cake	3.0	1.9	1.8
Cotton seed cake (decorticated)	6.4	2.9	2.2
Groundnut cake	7.3	1.5	1.3
Linseed cake	4.9	1.4	1.3
Niger cake	4.7	1.8	1.8
Rape seed cake	5.2	1.8	1.3
Safflower cake (decorticated)	7.9	2.2	1.9
Sesamum cake	6.2	2.0	1.2

Both types of oilcakes can be used as manure, but non-edible oilcakes are particularly used for horticultural crops. Nutrients in oilcakes become available to crops 7 to 10 days after application. They should be well-powdered before application for even distribution and faster decomposition.

Other Concentrated Organic Manures:

• Blood Meal: Dried and powdered blood meal serves as a good nitrogen source.
• Meat Meal: Made from dried and powdered meat of dead animals, providing a substantial nitrogen supply.

Nutrient Content in Organic Manures (%)

Organic Manures	N	P2O5	K2O
Blood meal	10 - 12	1 - 2	1.0
Meat meal	10.5	2.5	0.5
Fish meal	4 - 10	3 - 9	0.3 - 1.5
Horn and Hoof meal	13	-	-
Raw bone meal	3 - 4	20 - 25	-
Steamed bone meal	1 - 2	25 - 30	-

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