SOIL FERTILITY MANAGEMENT, Explain the meaning of soil fertility and a fertile soil.
- Outline the various methods of soil fertility management.
- State the advantages and disadvantages of each method of soil fertility.
Soil fertility is the capacity of the soil to supply mineral nutrient elements to crop.
The nutrients must be in adequate amounts and in suitable proportions to enhance crop production.
Meaning of soil fertility conservation
A fertile soil is that which contains adequate nutrient elements required by crops.
Characteristics of a Fertile Soil
1. High cation exchange capacity (C.E.C.)
2. Good water holding capacity
3. Adequate humus contents
4. Good granular (Spheroidal)
5. Easily tilled (good work-ability)
6. Essential elements available in required forms and amount.
Sometimes, a soil may not be able to produce good crops even if it is fertile. This is because of the inability of the soil to make nutrients available to the crops in the right amount.
This can happen because of several factors such as:
(a) Too much acids or bases in the soil. (b) Poor soil structure. (c) The proportion of the different soil particles present in the soil (Texture). (d) Climatic factors such as amount of rainfall and temperature. (e) The nature of the clay lattice. (f) Cation exchange capacity of the soil
2.2 Methods of Soil Fertility Management
There are several methods that can be used to maintain the fertility of the soil. They include bush fallowing, cover cropping,rotation cropping, application of organic and inorganic fertilizers.
1. Bush fallowing This is the practice of leaving a farm-land uncultivated for a period of time. This is to allow the soil to regain its lost nutrients in natural form. For instance, leaves from the shrubs and herbs drop and decay thus adding manure to the soil.
Advantages of organic manure soil fertility
- It can effectively maintain soil fertility in areas with low pressure organic n land. 2. It protects the soil against erosion. 3. Fallen leaves decompose to increase organic matter content of the soil.
- Evaporation of soil water and leaching of minerals are reduced. 5. There is also a build up of living organisms in the soil which arc useful for soil modification and granulation.
Disadvantages of organic manure
. It is a very slow process of managing soil fertility. 2. It does not suit the increasing demand for land due to population increase. 3. The period allowed for fallow is not enough for adequate replacement of lost nutrients.
- Cover Cropping This is the growing of crops purposely to provide cover for the. soil. Crops such as melon, cowpea (trailing type), groundnut, sweet potato, and others could be grown along side the main crops to provide cover for the soil. Others like pueraria. niucuna and centrosema can be used in plantations or on fallow lands.
Advantages of cover cropping in soil fertility management
- They protect the soil against erosion. 2. Evaporation of soil water is reduced. 3. They prevent the leaching of useful mineral elements in the soil. 4. They suppress weeds on the farmland 5. Their fallen leaves decompose to add organic matter to the soil.
- Where legumes are used, they help to increase the nitrogen content of the soil due to the action of root nodule bacteria 7. They can be worked into the soil as green 8. They help to maintain fairly stable soil fertility “‘
Disadvantages of cover cropping
- Cover crops compete with the main crops for nutrient elements and available water. 2. They increase the rate of loss of water in the soil through transpiration.
- Rotation Cropping
This is the growing of crops on a piece of land year after year in a definite order.
- The use of a good rotational system of cropping enables soil to be used continuously without rapid loss of essential nutrients.
- It is an ideal system to be used where land is scarce or may be land tenure system.
- It is a labour saving system as the same land is prepared for planting every year.
- Weeds are effectively checked .
- Erosion is reduced because the land is not exposed.
- It reduces the build up, of host specific diseases and pests.
The major disadvantage of this method is that continuous tillage of the surface soil renders it loose and easily eroded.’ 4. Organic Manuring Manures are plants and animal materials that (botanical names of crops) are added to the soil to supply nutrients needed for the growth of crops. A well decomposed organic matter is called humus. Humus is a rich source of plant nutrients suitable for vegetable gardening.
Types of Organic Manures
The major types of organic manures are green manure, form yard manure and compost manure
(i) Green manures: These are undecomposed green plants parts which are turned into the soil. Some plants are grown specifically to be worked or dug intp the ground to serve as source of plant nutrients.
Examples arc mucuna, centrosema. pueraria. calopogonium and fresh green weeds.
This is done mostly when they are young and succulent tor easy decomposition. It also involves the growing of leguminous plants for the purpose of soil improvement.
This is the reason for increase in yield of other crops planted after a legume, such as groundnut, pigeon peas, and cowpea which add nitrogen, check out nitrogen cycle here In the soil has been harvested.
(a) It provides organic matter to the soil to improve its physical condition. (b) It supplies nitrogen and other plant nutrients. (c) It protects the soil against erosion.
(d) It reduces the loss of nutrients through leaching.
(a) There is competition for basic nutrients and water. (b) They may harbour diseases and pests of crop plant. (c) It may be expensive to grow green manure plants. It is advised that plants to be used as green manure should (a) Easily establish. (b) Grow quickly. (c) Produce abundant succulent shoots and roots in a short time. (d) Easily cover the ground. (e) Grow on poor soils.
(ii) Farm yard manure: This is a mixture of animal droppings, urine, food remains and bedding or litter. Manure from poultry, goats and sheep are the richest forms of farm yard manure. They are followed by those of pigs, horse and cattle. The materials are heaped under a shed to decompose for sometime before use. They could be used direct on the farm.
They should be properly handled, as too much exposure may lead to breakdown of the nutrients. The more volatile constituents such as nitrogen could be lost as ammonia gas.
It is often better to mix manures from different types of animals to be used as pen manure than to apply only one type. The quality of farm yard manure depends on: (i) The species of animals producing the materials (ii) Age and condition of the animal. (iii) The type of feed given to the animal.
(iv) Nature and amount of litter. That is, whether absorbent materials are used as bedding (v) The handling and methods of storage before use on the farm. Farm yard manure can be applied by broadcasting before tillage especially when the soil is moist or wet. It can be spread on the bed and mixed with the soil before planting. read planting operation here
It contains ail the required plant nutrients.
- It is reasonably cheap as it can be obtained from the farm. 3. It has a lasting effect on the soil. 4. It binds loose sandy soil together. 5. It also loosens compact clay soils. 6. It enables the soil to absorb and retain moisture easily. you can also read types of soil here
1. It is very bulky. 2. It requires much labour during application. 3. It has the tendency to encourage rapid growth of weeds. (iii) Compost manure: This is the decayed plant and animal remains in heaps or stacks or pits, used as manure on the farm. The materials needed for compost making include grass cuttings, hedge trimmings, weeds, vegetable wastes, leaves and otter organic wastes from the kitchen. Ash or lime or animal dungs or old compost, chemical activators such as sulphate of ammonia are also added.
Young and succulent plant parts should be used instead of woody and tough parts. This is because decomposition is easier and contains much nutrients for healthy plant growth.
A suitable area of the farm, preferably near the edge, should be chosen. The area should not be water-logged.
When prepared during the dry season, there should be a nearby water source.
Methods of compost making:
Two methods can be used in compost making. These are the pit method and the stack or heap method.
The pit method is used in areas of low rainfall or in the dry season while the stack or heap method is used in high rainfall areas or during the rainy season. Whichever method is used , the processes as well as the materials used remain the same.
Processes of compost making
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1. Dig lour pits or peg out four areas.
2. Add kitchen wastes, yam peelings, orange skin and pulp, rotten fruits and anything that rots easily.
- Then, add grass cuttings. hedge trimmings, vegetable wastes and tilled or the desired height is compress.
- Repeat this process until the pit is filled or the desired height reached if heap method is used.
- Cover the top with soil to prevent the entering of flies.
- Insert a stick at one end or at the center in case of pit method. This is called a “tester”. It detects if decomposition is going on or not. The stick will be hot if there is decomposition after about 5 days or else, it will be cold.
Turn materials or the content of pit A or heap A into B after two weeks. Refill pit or heap A.
Repeat this step until pit or heap D is reached and the desired quantity obtained.
- Cover the final products with suitable materials until it is ready for use. This will prevent the loss of important nutrients due to strong sun or rain water. ‘Starters’ are materials used to initiate decomposition process of compost materials.
Examples are animal wastes, old compost or materials that rot easily. Chemicals such as sulphate of ammonia could be used to induce decaying process in the absence of starters. Such chemicals are called ‘activators”. Turning of compost in pit or stack.
Advantages of compost manure
- It provides sources of food to living organisms in the soil. like earthworms, termites and microbes. 2. It adds nutrients to the soil for increased crop yield,
- It improves the physical condition of the soil texture and structure and texture. 4. It helps to maintain equal amounts of acid and ha-. the soil. 5. It helps to conserve soil moisture and prevents erosion
- It has a modifying effect on soil temperature;
Disadvantages of compost manure
- It involves much labour in preparation. 2. It is time involving and not economic for use in large farms. 3. It could cause scorching if applied when not fully matured 4. It may introduce disease causing agents.
This will happen if not may properly handled or allowed to mature before use. Application of inorganic manures or fertilizers Inorganic manures or fertilizers are chemical substances in of powder, granules or crystals which are added to the soil to provide nutrients that are deficient. Fertilizers are manufactured in the industry from rocks and other materials.
Types of fertilizers used for soil fertility management
There are two types of fertilizers: (i) Straight or single or simple fertilizer: These are fertilizers that contain one of the major plant nutrients in the form plants can use.
They contain one primary element such as nitrogen, potassium and phosphorus in their composition. These are called the key nutrients.
Examples are sulphate of ammonia, urea, ammonia nitrate, sodium nitrate with nitrogen as the key nutrient.
Also, single super phosphate, concentrated super phosphate and calcium meta-phosphate all contain phosphorus as their key element.
Others are nitrate of potash (potassium (1) chloride), crude potash and caliphate-of-potash-alluvial -potassium-asthe-ir-primary element.
(ii) Mixed or complex or compound fertilizers:
These are fertilizers that contain two or more primary nutrient elements pill filler materials. The nutrients are in ratios and the ratio refers to the proportion of the major nutrients to one another.
Examples are N.P.K: 15:15:15, 20:20:20, N.P.K: Mg. 12: 12:17:2 and others Handling of fertilizers:
As a result of the inherent hazards of fertilizers such as stinging sensations, blisters, itching irritations and other skin diseases, care should be taken to avoid bodily contacts. the user should always put on gloves and protective clothing when handling fertilizers.
Storage of fertilizers: Fertilizers are stored in bags of synthetic fabrics which prevent entry of water and moist air that could lead to dissolution.
Tarpaulins should be used to give additional protection to the fertilizers stored at ports warehouses, field depots of the Ministry of Agriculture and other agencies.
Farmers should construct a simple fertilizer store among their stead. They should be stored differently according to types for easy identification and access. Platforms of wood should be made on which the bags are stacked, up to a considerable height, to avoid slippage and allow for easy stock taking. It should not rest on the wail. Air circulation should be encouraged in the store.
Advantages of fertilizers:
- They bring about increase in crop yield.
- They increase farm income.
- They increase the productivity of poor soils.
- They are easily transported to where they are needed compared to organic manures.
- They are used on large scale.
- The nutrients in fertilizers are readily available to crops.
Disadvantages of fertilizers
- Fertilizers are easily leached in the soil. 2. Some fertilizers leave acidic residues in the soil. 3. Inorganic manures do not improve soil structure. 4. Some of the nutrients are easily lost as gases under intense heat of the sun.
Example is ammonia.
- Fertilizers are expensive to procure. 6. They are sometimes not available at the time of need.
Methods of applying fertilizers
- Broadcasting: This is where fertilizer is evenly spread on the farmland. It could be done before ploughing or tillage to incorporate it into the soil.
- Side dressing or application: This is where small quantity of fertilizer is placed on one or two sides of individual crop.
- Ring application: A shallow trench is dug round individual crop a few centimetres away from the stem. Fertilizer is then sprinkled in the trench and covered with soil.
- Row application: This is where fertilizer is applied in row few centimetres from the crops. It is suitable when crops are planted in rows
- Top dressing: This is where fertilizer is applied to the surface soil within the reach of the roots of crops during the growing stage.
- Foliar application: This is where soluble fertilizers are applied as sprays on the leaves of crops.
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