Agriculture JSS2
Week 8
Topic: SOIL FERTILITY
Contents:
What is Soil Fertility?
Plant Nutrients
Ways of Maintaining Soil Fertility
A. What is Soil Fertility?
Soil fertility is the ability of the soil to apply all the necessary soil nutrients required by the plants for it growth and development in right proportion and absolve-able form.
Soil fertility refers to the ability of a soil related to plants its ease of tillage, fitness of seedbed, and impedance to seedling emergence and root penetration by providing nutrients and suitable soil structure to support the plants/trees growth.
The fertility of the soil can be considered in different ways, depending on land use. In intensively managed agricultural and horticultural systems, and even in forestry, soil fertility can be defined in terms of the value of products produced relevant to inputs used (including economic aspects of nutrient budgeting). Alternatively, the emphasis may be on quality or productivity.
i.e. The fertility of soil is related to its capacity to produce a product.
In many natural ecosystems, the value of land use may not be clearly defined, and a different definition of soil fertility may be more suitable.
i.e. The fertility of soil is related to its capacity to support a particular natural community of plants.
Another view might emphasize the concept of sustainability.
i.e. The fertility of a soil is related to its capacity to maintain consistent output with minimal input.
Thus, the concept of soil fertility is most useful when it is used in a specific context. However, in all contexts, soil fertility depends on physical, chemical and biological characteristics.
A fertile soil has the following properties:
- It is rich in nutrients necessary for basic plant nutrition, including nitrogen, phosphorus and potassium
- It contains sufficient minerals (trace elements) for plant nutrition, including boron, chlorine, cobalt, copper, iron, manganese, magnesium, molybdenum, sulfur and zinc.
- It contains soil organic matter that improves soil structure and soil moisture retention.
- Soil pH is in the range 6.0 to 6.8 for most plants but some prefer acid or alkaline conditions.
- Good soil structure, creating well drained soil, but some soils are wetter (as for producing rice) or drier (as for producing plants susceptible to fungi or rot, such as agave).
- A range of microorganisms that support plant growth.
- It often contains large amounts of topsoil.
B. Plant Nutrients
The mineral elements required by plant in large quantity are called macro nutrients, while these required in small quantities are called micro-nutrients e.g zinc.
Macronutrients
Macronutrients can be broken into two more groups: Primary and Secondary nutrients.
The Primary nutrients are nitrogen (N), phosphorus (P), and potassium (K). These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.
The Secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S). There are usually enough of these nutrients in the soil so fertilization is not always needed. Also, large amounts of Calcium and Magnesium are added when lime is applied to acidic soils. Sulfur is usually found in sufficient amounts from the slow decomposition of soil organic matter, an important reason for not throwing out grass clippings and leaves.
Micronutrients
Micronutrients are those elements essential for plant growth which are needed in only very small (micro) quantities. These elements are sometimes called minor elements or trace elements, but use of the term micronutrient is encouraged by the American Society of Agronomy and the Soil Science Society of America. The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients (as well as macronutrients) to growing plants.
C. Ways of Maintaining Soil Fertility
- Use of organic manure-Green , animal, farmyard and compost manure
- Inorganic fertilizer application
- Bush fallowing
- Cover cropping
- Crop rotation
- Practice mixed cropping
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