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.
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.
Every plant nutrient, whether required in large or small amounts, has a specific role in plant growth and food production. One nutrient cannot be substituted for another.