Agriculture JSS2
Week 9
Topic: MAINTAINING SOIL FERTILITY
Contents:
- Use of organic manure-Green , animal, farmyard and compost manure
- Inorganic fertilizer application
- Bush fallowing
- Liming
- Crop rotation
- Alley cropping
There are various ways of maintaining soil fertility. This includes: Use of organic manure-Green , animal, farmyard and compost manure, Inorganic fertilizer application, Bush fallowing, Liming, Crop rotation and Alley cropping.
Use of organic manure-Green , animal, farmyard and compost manure
Manure is organic matter, mostly derived from animal feces except in the case of green manure, which can be used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web. It is also a product obtained after decomposition of organic matter like cow dung which replenishes the soil with essential elements and add humus to the soil.
Inorganic Fertilizer Application
A fertilizer (or fertiliser in British English) is any material of natural or synthetic origin (other than liming materials) that is applied to soils or to plant tissues (usually leaves) to supply one or more plant nutrients essential to the growth of plants. Conservative estimates report 30 to 50% of crop yields are attributed to natural or synthetic commercial fertilizer.
Bush fallowing
A type of subsistence agriculture in which land is cultivated for a period of time and then left uncultivated for several years so that its fertility will be restored.
Manuring
Animal manures or farmyard manure (FYM). This is the use of dung, urine and bedding materials (if the animals are kept inside). FYM varies depending on type of animal, their age and condition, food consumed and how the manure is stored.
Characteristics of Farmyard Manure include:
- Low in mineral nutrients but high in organic matter
- Often low in Phosphorus, may need to combine with phosphate fertilizer
- Composition varied according to source
Animal waste. Including offal, dried blood and bone, unused hoof and horn. Often used in temperate climates by gardeners, care must be taken not to spread disease.
Human excreta and faeces and food waste. Latrine waste can be used after two years buried in a pit.
Green manure – Some crops are grown to provide organic matter. Leguminous crops fix nitrogen in the soil. When cut and composted into the soil or cultivated when they are young, they increase the organic matter content, improve soil structure, make phosphorus and certain trace elements available to plants, check erosion and leaching and help control weeds.
Crop rotation
Crop rotation is the practice of growing a series of dissimilar/different types of crops in the same area in sequential seasons.
Crop rotation gives various nutrients to the soil. A traditional element of crop rotation is the replenishment of nitrogen through the use of green manure in sequence with cereals and other crops. Crop rotation also mitigates the build-up of pathogens and pests that often occurs when one species is continuously cropped, and can also improve soil structure and fertility by alternating deep-rooted and shallow-rooted plants. Crop rotation is one component of polyculture.
Compost Making
Composting is the rotting down of plant and animal remains before it is applied to the soil. The compost should be mixed with available manure and allowed to decompose together for a maximum of two months before applying to the soil. Composting is safer because the heat generated whilst the material breaks down kills diseases and weeds and seeds and the mixture has a better balance of all the soil needs.
Building a compost heap is done in four layers:
Bottom layer – the base is made of stones and sticks to allow drainage and aeration
- Next to bottom – crop residues, usually the bulk ingredient
- Next to top – can be made of animal dung, egg shells and cooking waste
- Top layer – made of soil about 25mm deep with wood ash, nitro chalk and super-phosphate if available.
The layers on top of the base need turning once or twice during the composting period. Compost needs to be kept moist, either by rainwater or watering if necessary, but must not become too wet or it will rot. Too much rain will also leach out the nutrients
Liming
Liming is the application of calcium- and magnesium-rich materials to soil in various forms, including marl, chalk, limestone, or hydrated lime. This neutralizes soil acidity and increases activity of soil bacteria.
Mixed Cropping
Different crops are grown in the same field which helps prevent soil erosion and controls the spread of soil-borne plant disease. Leguminous plants will add nitrate to the soil which improves fertility. Deep rooted crops will help improve the soil structure.
Alley Cropping
This is where the crops are grown between rows of trees, some of which can fix nitrogen in the soil. The roots fix nitrogen, then the trees are cut back with the leaves being incorporated into the soil as green manure.
Exercise
- What is the difference between mixed cropping and alley cropping?
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