Organic Manures

Manures are organic materials derived from animal, human, and plant residues that are used to improve soil fertility and crop productivity by supplying plant nutrients in a form that plants can absorb after decomposition. The use of manures has been a long-standing practice in agriculture, with a history dating back to ancient times. They differ from fertilizers, which are typically synthetic or naturally occurring chemicals that provide plant nutrients. Manures are a rich source of organic matter, which not only supplies essential nutrients but also improves soil health, enhances water retention, and boosts microbial activity in the soil.

Major Sources of Manures

Manures come from a variety of sources:

1. Cattle Shed Wastes: These include dung, urine, and slurry from biogas plants. These organic wastes can be used to create farmyard manure (FYM).
2. Human Habitation Wastes: These include night soil, human urine, town refuse, sewage, sludge, and sullage.
3. Poultry Waste: This includes the droppings of poultry, which are rich in nutrients.
4. Slaughterhouse Wastes: These include bone meal, meat meal, blood meal, horn and hoof meal, and fish waste, all of which are rich in nitrogen and other essential nutrients.
5. Byproducts of Agro-industries: These include oil cakes, bagasse, press mud, and fruit/vegetable processing wastes.
6. Crop Wastes: These include materials like sugarcane trash, stubbles, and other plant residues that can be used as green manure.
7. Water Hyacinth, Weeds, and Tank Silt: These can also be used to enrich the soil.
8. Green Manure Crops and Green Leaf Manuring Material: Crops like legumes and other plants are grown specifically to be plowed into the soil to improve its nutrient content.

Types of Manures

Manures are generally categorized into two broad types based on their nutrient content:

1. Bulky Organic Manures
2. Concentrated Organic Manures

Bulky Organic Manures (BOM) are organic materials that are rich in organic matter and are applied to the soil in large quantities. These manures are primarily used to improve the physical properties of the soil, enhance microbial activity, and increase the availability of nutrients for plants. Unlike concentrated manures, which are nutrient-dense, bulky organic manures provide a slow, steady supply of nutrients over time. They are typically lower in nutrient content but are valuable for improving soil structure, fertility, and overall soil health.

Key Characteristics of Bulky Organic Manures

• Low Nutrient Concentration: These manures are generally low in nutrients compared to concentrated manures, but they are rich in organic matter.
• Large Application Volumes: They are applied in large quantities to ensure that the soil receives enough nutrients to support plant growth.
• Slow Release of Nutrients: The nutrients in bulky organic manures are released slowly as the organic matter decomposes, ensuring long-term availability of nutrients.
• Soil Structure Improvement: One of the key benefits of bulky organic manures is their ability to improve soil structure, making it looser and more porous. This leads to better root penetration, water infiltration, and aeration.
• Increase in Soil Microbial Activity: The addition of organic matter supports soil microbes, which play a crucial role in nutrient cycling and the overall health of the soil ecosystem.

Common Types of Bulky Organic Manures

• Farmyard Manure (FYM)
  • Composition: Farmyard manure is made from a mixture of animal dung, urine, and bedding material like straw or hay. The manure is composted over time, resulting in a nutrient-rich material.
  • Nutrient Content: Typically contains about 0.5% nitrogen (N), 0.2% phosphorus (P), and 0.5% potassium (K).
  • Benefits: FYM is known for improving soil structure, enhancing moisture retention, and providing essential nutrients to crops. It also enhances soil microbial activity, which helps in the breakdown of organic matter and the release of nutrients.

• Compost
  • Composition: Compost is made from decomposed organic materials such as crop residues, kitchen waste, leaves, and other plant matter. It can be prepared through either aerobic (with oxygen) or anaerobic (without oxygen) processes.
  • Nutrient Content: The nutrient content can vary depending on the materials used but is generally low in comparison to concentrated fertilizers.
  • Benefits: Compost enriches the soil with organic matter, improves its structure, and enhances the availability of nutrients. It also increases soil moisture retention and promotes the growth of beneficial soil organisms.

• Green Manure
  • Composition: Green manure involves growing specific crops (typically legumes like cowpea, groundnut, or sesbania) that are incorporated into the soil while they are still green and have not yet matured. These crops are often leguminous, as they can fix nitrogen from the atmosphere.
  • Nutrient Content: Green manure crops are a good source of nitrogen, phosphorus, and other micronutrients.
  • Benefits: The incorporation of green manure adds a substantial amount of nitrogen to the soil, improves its organic matter content, and increases microbial activity. It also helps in improving soil structure and reducing soil erosion.

• Crop Residues
  • Composition: This includes leftover plant material after harvesting crops, such as straw, leaves, and stubble. These residues can be left in the field or collected for composting.
  • Nutrient Content: The nutrient content depends on the type of crop and the stage of decomposition. Crop residues are rich in carbon and provide essential nutrients when decomposed.
  • Benefits: Crop residues add valuable organic matter to the soil, improving its fertility and structure. They also enhance water-holding capacity and help in reducing erosion by providing a mulch layer.

• Animal Manure
  • Composition: Animal manure comes from various farm animals, such as cows, goats, sheep, and poultry. It consists of dung, urine, and bedding material.
  • Nutrient Content: Animal manure varies in nutrient content depending on the animal and its diet. Generally, it contains nitrogen, phosphorus, and potassium in varying proportions.
  • Benefits: Animal manure is an excellent source of organic matter and helps in improving soil structure, water retention, and nutrient availability. It also supports beneficial microorganisms that promote soil health.

Advantages of Bulky Organic Manures

1. Improvement of Soil Structure: Organic matter in bulky manures helps to break up compacted soils, making them more friable and improving root growth. It enhances soil aeration, ensuring that plant roots have better access to oxygen.
2. Increased Water Holding Capacity: The organic matter in bulky manures helps to improve the water retention capacity of the soil. This is particularly useful in sandy soils that tend to drain water quickly.
3. Enhanced Nutrient Availability: Although bulky organic manures release nutrients slowly, they provide a continuous supply of essential plant nutrients (nitrogen, phosphorus, and potassium) over a longer period.
4. Microbial Activity: Organic manures stimulate soil microbial activity, which in turn helps decompose organic materials, release nutrients, and suppress harmful pathogens.
5. Reduction of Soil Erosion: When applied as mulch, bulky organic manures help protect the soil from wind and water erosion. They also improve the soil’s ability to resist erosion by improving its structure.
6. Sustainability and Reduced Dependency on Chemical Fertilizers: The use of bulky organic manures helps reduce reliance on synthetic fertilizers, which can lead to soil degradation over time. Organic manures improve long-term soil fertility and sustainability.

Concentrated Organic Manures (COM) are organic materials that contain a high concentration of nutrients in a relatively small volume compared to bulky organic manures. These manures are typically rich in essential nutrients like nitrogen (N), phosphorus (P), and potassium (K), and are used in smaller quantities than bulky manures. They provide a more immediate supply of nutrients to plants and are often used to supplement the nutrient supply of soils that require higher levels of specific nutrients.

Key Characteristics of Concentrated Organic Manures

• High Nutrient Content: Concentrated organic manures are rich in essential nutrients, which makes them effective in providing a quick nutrient boost to plants.
• Low Volume Application: These manures are used in smaller quantities compared to bulky organic manures, making them more efficient in terms of the volume required for application.
• Faster Nutrient Release: Due to their high nutrient concentration, concentrated organic manures release nutrients more rapidly compared to bulky manures, making them ideal for crops with high nutrient demands.
• Better Nutrient Efficiency: These manures can be more efficient at addressing specific nutrient deficiencies in the soil, especially when targeting particular nutrient needs.

Common Types of Concentrated Organic Manures

• Poultry Manure
  • Composition: Poultry manure is derived from the droppings of chickens, turkeys, and other poultry. It often contains a combination of manure, bedding material, and sometimes feed particles.
  • Nutrient Content: Poultry manure is highly concentrated in nutrients, especially nitrogen, phosphorus, and potassium. It typically contains about 1.5% nitrogen, 1.1% phosphorus, and 0.8% potassium.
  • Benefits: It provides a rich source of nutrients, especially nitrogen, which is vital for promoting leafy growth. Poultry manure also helps in improving soil texture and increasing microbial activity.
  • Precaution: Fresh poultry manure should be composted before use, as it can be too hot for plants and may burn crops due to its high nitrogen content.

• Vermicompost
  • Composition: Vermicompost is produced by the decomposition of organic materials (such as plant matter) by earthworms. This process results in a nutrient-rich, dark, crumbly material.
  • Nutrient Content: Vermicompost contains balanced nutrients, including nitrogen, phosphorus, potassium, calcium, and magnesium. It typically has about 1.5% nitrogen, 1.0% phosphorus, and 1.5% potassium.
  • Benefits: Vermicompost is highly valued for its ability to improve soil fertility, structure, and water-holding capacity. It also enhances microbial activity and provides nutrients that are readily available to plants.
  • Precaution: Vermicompost is considered a slow-release fertilizer and is best used as a supplement rather than a sole nutrient source.

• Bone Meal
  • Composition: Bone meal is made from finely ground animal bones, typically from cattle or poultry. It is a byproduct of the meat-processing industry.
  • Nutrient Content: Bone meal is an excellent source of phosphorus and calcium. It typically contains 12-15% phosphorus and around 20% calcium.
  • Benefits: Bone meal is primarily used to promote strong root development and flowering in plants. It is particularly useful for plants like bulbs, vegetables, and flowering shrubs that require a high phosphorus content.
  • Precaution: Bone meal has a slow nutrient release rate, and it can be more effective when incorporated into the soil during planting.

• Fish Meal
• • Composition: Fish meal is made by grinding fish or fish byproducts such as fish heads, tails, and bones. It is rich in protein, oils, and nutrients.
  • Nutrient Content: Fish meal is rich in nitrogen, phosphorus, and trace elements. It typically contains 7-10% nitrogen, 3-4% phosphorus, and 1-3% potassium.
  • Benefits: Fish meal is an excellent source of slow-release nitrogen and phosphorus, making it effective for improving plant growth and increasing flower and fruit production.
  • Precaution: Fish meal has a strong odor that may attract pests, and it can be costly compared to other organic manures.

• Blood Meal
  • Composition: Blood meal is made from dried blood, typically from cattle, poultry, or other livestock. It is a concentrated source of nitrogen.
  • Nutrient Content: Blood meal is very high in nitrogen, often containing about 12-15% nitrogen, along with small amounts of phosphorus and potassium.
  • Benefits: Blood meal is a fast-acting nitrogen fertilizer that promotes lush green growth in plants. It is particularly useful for leafy vegetables and other crops that require significant nitrogen.
  • Precaution: Because of its high nitrogen content, blood meal should be used cautiously to avoid burning plants. It should be applied in moderation.

• Bone Char
  • Composition: Bone char is produced by heating animal bones at high temperatures in the absence of air, a process known as pyrolysis. It is primarily used for soil amendments.
  • Nutrient Content: Bone char is rich in calcium and phosphorus, providing a slow-release form of both nutrients.
  • Benefits: Bone char can improve soil structure and fertility, particularly in acidic soils. It is often used to raise the pH of the soil in acidic conditions.
  • Precaution: Bone char has limited availability of nitrogen and potassium, so it is usually combined with other fertilizers for a more balanced nutrient supply.

Advantages of Concentrated Organic Manures

1. High Nutrient Density: Concentrated organic manures are nutrient-rich and can deliver a high amount of essential plant nutrients with relatively small quantities, making them more efficient in terms of application.
2. Quick Nutrient Release: Due to their nutrient concentration, concentrated manures provide fast nutrient availability to plants, especially those with high nutrient demands, such as vegetables and flowering plants.
3. Improved Plant Growth: These manures support vigorous plant growth by supplying essential nutrients such as nitrogen, phosphorus, and potassium. They are particularly useful in promoting root development, flowering, and fruiting.
4. Better Soil Fertility Management: Concentrated organic manures allow for targeted nutrient application, addressing specific deficiencies in the soil, thus improving the overall soil fertility in a more precise and efficient manner.
5. Reduction in Fertilizer Usage: Using concentrated organic manures reduces the need for chemical fertilizers, thus contributing to environmentally friendly farming practices and reducing the risk of soil and water pollution.
6. Soil Microbial Activity: While concentrated manures release nutrients quickly, they still support microbial activity, which plays a role in decomposing organic matter and enhancing soil health.