Learning objectives
By the end of this lesson, you should be able to:
- Explain the meaning of organic manure, organic matter, and humus.
- Describe the importance of the organic matter in the soil.
- Describe the different types of organic manures, their advantages, and disadvantages.
Some Important Definitions
Organic matter is a decomposable substance made up of plant and animal remains.
Humus is the non-decomposable material like cellulose and lignin, found in organic matter.
Organic manures are those made from plant and animal remains.
Importance of organic matter in the soil
- It improves soil fertility when it decays.
- It improves water infiltration and retention capacity in the soil.
- It encourages microbial activities in the soil.
- it improves soil aeration and drainage.
- Its dark color improves the ability of soil to absorb heat.
- It improves soil structure by binding the soil particles together.
- It buffers and moderates soil pH by preventing rapid chemical changes.
- It reduces the toxicity of the soil.
- It improves the cation-exchange capacity of the soil.
- It prevents the leaching of nutrients.
Benefits of humus in the soil
- Humus is spongy and therefore improves water retention and soil aeration.
- It gives the soil a dark color that helps it to absorb and retain heat.
- It improves soil structure since it cements clay and other silty particles.
Types of organic manure
I. Farmyard manure
Farmyard manure is also called pen or muck manure. It is a mixture of animal wastes and animal bedding which is usually straws that have absorbed urine and feces.
Following factors affect the quality of farmyard manure:
- Quality of food given to the animal.
- Type of bedding or litter used.
- Type of species of the animal.
- Age of the manure.
- Method of storage.
- Age of the animal.
Advantages of farmyard manure
- It improves soil structure.
- Farmyard manure improves soil structure by binding the soil particles together.
- It promotes microbial activity in the soil.
- It imparts a dark color on the soil, which helps to regulate soil temperature.
- It supplies more than one plant nutrient on decomposition.
- It has a long residual effect and releases nutrients slowly due to its slow rate of decomposition.
- It improves the water retention capacity of the soil.
- It is not leached easily.
- Farmyard manure buffers or moderates soil pH and improves its cation-exchange capacity.
Disadvantages of farmyard manure
- It is bulky and hence costly to transport.
- It has fewer nutrients per given volume or quantity.
- It requires a lot of labor to handle and apply.
- The release of nutrients is by decomposition and is very slow.
- It can introduce pests and weeds on farms.
- It is required in large amounts.
- It may burn crop roots if used immediately after making.
- Farmyard manure may harbor and spread diseases to animals and crops, for example, salmonella infection in animals.
II. Green manure
Green manure is obtained by growing a crop, particularly legumes, up to the flowering stage and then incorporating it back to the soil.
Characteristics of a good green-manuring crop
- It should be highly vegetative and less woody for faster decomposition.
- It should be fast-growing.
- It should be rich in nutrient content.
- It should yield a large quantity of green foliage in a short period.
- It should be free from pests and diseases.
- It should be adaptable to a wide range of conditions.
- It should have a deep, well-developed root system so that it brings nutrients from the lower layers to the surface.
Advantages of green manure
- It supplies organic matter to the soil.
- Soil erosion is reduced by soil coverage.
- Legumes used to prepare the manure fix nitrogen in the soil.
- It improves the activities of soil micro-organisms.
Disadvantages of using green manure
- Green manure may delay the planting of the main crop.
- Intensive land use leaves no room for its cultivation.
- It releases nutrients slowly, and may thus not be of immediate benefit to crops.
- Green-manure crops absorb the available moisture at the expense of the main crop.
- It is expensive to prepare, compared to artificial fertilizers.
- It is laborious and costly to grow and plow crops into the soil.
III. Compost manure
This is a type of manure that consists of a partially decomposed mixture of household refuse and crop residues, with or without the addition of some animal or human waste. Compost manure is usually subjected to a controlled process of decomposition.
Characteristics of materials used in the preparation of compost manure
- They should be free from pests and diseases.
- They should not be from over-mature plants as these take longer to decay.
- They should be free from weeds.
- They should have relatively high moisture and nutrient content.
Factors to consider when siting a compost pit
The following factors should be considered when siting a compost pit:
- It should be sited in a well-drained area that is free from waterlogging.
- It should be in a well-sheltered place.
- It should be near the place where the compost will be used.
- The site should be accessible.
- It should not be sited on the windward side of the farmhouse.
Factors that determine the quality of compost manure
- Method of storage.
- Quality and variety of material used.
- Size of the pit or heap.
- The period taken for the material to decompose.
- Rate of mixing to allow air circulation.
- Degree of precaution against rain, excessive temperature, and drying.
Advantages of compost manure
- The materials used to make compost manure are locally available.
- It improves soil structure by binding the soil particles.
- Its dull color helps to regulate soil temperature.
- It helps to regulate soil pH.
- It promotes microbial activity in the soil.
- It is cheaper than using artificial fertilizers.
- It improves soil aeration.
- It is rich in a variety of nutrients.
Disadvantages of compost manure
- It releases nutrients slowly into the soil.
- It is required in large quantities.
- It is bulky and hence expensive to transport.
- It requires a lot of labor to prepare.
- It may contain weed seeds, pests, and disease pathogens.
- It takes a long time to prepare.
- It is difficult to determine the amount of nutrients in the quantity applied.
