Natural and Synthetic Fertilizer

a. Natural Fertilizers. The natural fertilizers are materials derived from plants and animals. It is divided into two major groups; organic fertilizers and organic manures.

• Organic Fertilizers. All the organic fertilizers supply nitrogen and phosphorus but are more expensive than the synthetic fertilizers, so it is rarely being used in modern agriculture. However, they are often preferred by vegetable and flower growers because they act a little more slowly and, since most are insoluble in water, they do not damage germinating seeds and young plants.

• Organic Manures. The organic manures are bulkier than the organic fertilizers and contain relatively lower amounts of plant nutrients. The best known of the organic manures is farm manure, the excrement of livestock. The composition of farm manure depends on the type of animal that produced it and how they were kept and fed. Chicken manures, which are drier and richer, supply about three times as much as nitrogen and phosphorus per ton as other manures but only about the same amount of potassium. When organic manures are used regularly, micronutrient deficiencies are rare, and the organic matter of the soil increases.

• Sewage sludge (residual material left from wastewater treatment processes) and other urban wastes are often proposed as organic manures, usually to aid in their disposal. Sludge generally contains from 1% to 2% nitrogen and phosphorus pentoxide and even less potash, but specially treated sludges are richer and more useful to crops. The dusts and pulverized refuse from cities are poorer in nitrogen and phosphorus and are of little value as manures. A serious hazard with all sludges and refuse materials is that they often contain enough metals such as lead, copper, and zinc to be toxic to plants.

b. Synthetic Fertilizers: Synthetic fertilizers today are composed mainly of nitrogen, phosphorus and potassium compounds with secondary nutrients added. The use of synthetic fertilizer has greatly improved the quality and quantity of the food available today, but their long term used has some negative effect in the environment according to some environmentalist.This kind of fertilizer comes in two forms

• Solid - Most solid chemical fertilizers are in the form of granules, it store well and are easy to handle and apply. Formerly, chemical fertilizers were made mostly in the form of powders, but they were often too dusty which is harder to apply especially is it's windy.
• Liquid - Liquid fertilizers is becoming popular today, it provides about one-fifth of the nitrogen fertilizer used throughout the world.

Hazards of Fertilizer Use: Fertilizer has no harmful effects on the soil, the yield or quality of crops, or the health of the consumer if they are used properly. Problem arise when farmers use more fertilizer than what is required, it damages their crops and sometimes affects the people and animals that eat them. It is also believed that the accumulation of fertilizers in lakes, streams, and other bodies of water may cause eutrophication, which increases the growth of algae and other aquatic plants.