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AGRICULTURAL SCIENCE JSS 2 WEEK 1 SOIL FERTILITY AND FERTILITY MANAGEMENT LESSON: 1 SOIL FERTILITY: This is the ability of the soil to supply adequate major nutrients to plants in a required quantity. Nutrients are essential elements for the plant body to function well. They are called essential elements because without them the crop will not grow well and may even die. Plants nutrients are classed into; 1. Major(Macro) Nutrients: These are required by plants in relatively large quantities. Examples; Nitrogen, Potassium, magnesium, calcium etc. Below are some of the essential elements, their functions and deficiency symptoms (signs) ELEMENTS, FUNCTIONS AND DEFICIENCY ELEMENTS Nitrogen FUNCTIONS Rapid plant growth and formation of chlorophyll Calcium Neutralizes acidity in plants and strengthen plant wall Phosphorus Helps plants resist diseases and for seed germination Potassium Neutralizes organic acids in plants and strengthen stem and stalk of plants. Aids uptake of nitrate from the soil. Magnesium Promotes formation of fat and oil. Normal cell division and chlorophyll Sulphur Constitute plant protein, chlorophyll formation and nitrogen fixation DEFICIENCY SYMPTOMS Stunted growth and yellowing of leaves Curling of leaves Purple coloration of leaves stunted growth Yellowing between leaf veins. Reduced plant growth, seed and fruit development. Yellowing between leaf veins and stunted growth. Premature ageing of plant. Stunted growth. Yellowing of leaves Micro or Minor Nutrients: These are needed in small quantities. They act as coenzymes. Examples: iron, manganese, boron etc. Below are some of the essential elements, their functions and deficiency symptoms (signs) Element Iron (Fe) Manganese and copper Zinc Boron Molybdenum Function Chlorophyll formation and protein synthesis Protein and enzyme constituent. And for photosynthesis Growth of plant hormones. Reproduction process. Increase yield. Seed and fruit formation Nitrogen fixation and increased soil pH level Deficiency Symptoms Restricted growth Pale green colouration of leaves. Death of young leaf tip. Production of small leaves Poor plant growth, reduced rate of water absorption Retarded growth and premature flower drop. Ways Of Maintaining Soil Fertility 1. Bush Fallowing: Bush fallowing is farming technique in which the farm land is not cultivated for a period of time ,so that the soil nutrients can be replenished. The soil is allowed to rest for sometimes before it is being used again. Farmers adopt this method because it is simple, cheap and helps to check pests and diseases. However, this is only possible where land is abundant. It discourages land improvement. 2. Cover Cropping: This is the cultivation of fast growing crops that spread on the soil surface to provide cover over the soil. Example: mucuna,centrosema ,calpogonium, pueraria stylosanthes etc. The crops prevent loss of nutrients through erosion and evaporation of excess water. It also helps to fix atmospheric nitrogen into the soil. However, they compete with other crops for nutrients. 3. Crop Rotation: Planting different types of crops on a piece of land every season following a sequential order. The different crops grown during a given year or season are collectively called COURSE. 4. Organic Manuring: This is the application of plant and animal residues to improve the fertility of the soil. The various types include; i. Green Manure:It is obtained by ploughing(turning)into the soil young plants which decay to add to the soil nutrients. ii. Compost manure: is obtained from the decaying of plant and animal materials in a pit. iii. Farm yard manure: is a mixture of animal wastes with plant materials used as animal bedding. Organic manuring helps to check soil erosion, stimulate microbial activities and conserve soil moisture. However, it is bulky and difficult to handle, the quantity to be apply to crops is difficult to estimate. 5. Inorganic Manure/ Fertilizer: These are chemical substances which contain plant nutrients. Types of inorganic manure include; a. Simple or straight fertilizers:These contain only one major nutrients .Examples are nitrogenous fertilizer(nitrogen), phosphatic fertilizerphosphorus )and potash fertilizer(potassium). b. Compound or mixed fertilizer: This contains two or more major nutrients in different proportions. Examples are NPK fertilizer which contains Nitrogen, Phosphorus and Potassium in the ratio 15:15:15. Method of fertilizer application includes; broadcasting, ring method, foliar spray, row side placement and top dressing. Organic fertilizer improves soil pH, and improves soil structure. However, it lowers soil pH, reduces microbial activities in the soil, and it is expensive to purchase. 6. Liming: The process of adding material rich in Calcium or Magnesium( such as lime, wood ash etc) to the soil to reduce its acidity. 7. Mulching: This is the act of covering the soil surface with materials such as dry grass, crop residues, polythene sheets etc to reduce the impact of rain and sunlight on the soil. Assignment. a. Define the term soil fertility. b. What is the difference between macro-nutrient and micro-nutrient ? c. Why are some elements regarded as essential elements ? Please submit the assignment to MISS OGBA through ( E-MAIL ADDRESS) [email protected]