Fertilizers increase crop yields

Plants need sun, water and nutrients to grow. The nutrients can be taken from air or soil. If there is an ample supply of nutrients in the soil, crops are more likely to grow well and produce high yields. If even one of the nutrients needed is in short supply, plant growth is limited and crop yields are reduced.

Fertilizers are needed to obtain high yields because they supply crops with the nutrients the soil lacks. By adding fertilizers, crop yields can often be doubled or even tripled. The UN Food and Agriculture Organization (FAO) Fertilizer Programme undertook extensive demonstrations and trials in 40 countries over a period of 25 years. The weighted average increase resulting from the best fertilizer treatment for wheat was about 60%.

Fertilizers contribute to efficient use of land and water

Fertilizers ensure the most effective use of both land and water. Where rainfall is low or crops are irrigated, the yield per unit of water used may be more than doubled and the rooting depth of the crop increased through fertilizer application.

Organic manure improves fertilizer efficiency

Before fertilizers are applied, all available plant nutrient sources (e.g. cow-dung, pig excreta, chicken droppings, vegetable wastes, straz, maize stover and organic materials) should be used. They should be well composted and allowed to decompose before being applied to the soil.

Although the nutrient content of organic manure is low and variable, it is very valuable. It increases soil fertility by:

• improving soil structure
• reducing soil erosion
• regulating soil temperature
• helping soil to store more moisture
• providing food for soil organisms

Integrated Plant Nutrition Systems

The application of organic manure is often the basis for successful use of mineral fertilizers. The combination of organic manure, other organic matter and mineral fertilizers provides ideal conditions for crop growth. Organic manure and other organic matter improve soil properties. Mineral fertilizers supply the needed plant nutrients .

Because of the level of crop production required for farmers to respond adequately to market demand, the use of organic manure alone is not sufficient. Mineral fertilizers are also needed. Even in countries where a high proportion of organic waste is used as manure (and to supply other organic matter), mineral fertilizer consumption has risen steadily.