Frequently Asked Questions About Fertilizers

What are fertilizers?

Think of fertilizers as plant food. Fertilizers are combinations of the nutrients that plants must have to grow, in a form they can use. The primary nutrients in fertilizers are three essential elements: nitrogen (N), phosphorus (P) and potassium (K), which are often combined into an NPK blend. Secondary nutrients (sulfur, calcium and magnesium) are needed in smaller amounts for normal plant growth. Micronutrients are also needed but in even smaller quantities. Micronutrients include boron, chlorine, copper, iron, manganese, molybdenum, nickel and zinc. People require the same nutrients. These plant nutrients can be supplied through organic fertilizers such as plant residues or livestock manure, or mineral fertilizers, which are chemically processed to meet crop needs.


Plants generally need more nitrogen than phosphorus or potassium. Thus, nitrogen is the major component of most fertilizers. Phosphorus is the plant world’s equivalent of carbohydrates – it provides energy for plants to thrive. Potassium helps plants fight stresses and disease and grow strong stalks.

Most nitrogen in mineral fertilizers is drawn from the air – which is 80 percent nitrogen – through an industrial process, and then highly pressurized to convert the nitrogen to ammonia. The ammonia is then converted to various nitrogen-based fertilizers, such as granular urea and liquid ammonia. Phosphorus, potassium and most secondary or trace nutrients are mined from the ground.

All plant nutrients, whether found in organic or mineral fertilizers, are the same, but mineral fertilizers have the advantage of concentration, and nutrients can be blended to meet specifications. Thus, mineral fertilizers can be better “targeted” to meet the nutritional needs of specific plants and soils.

Why do we need fertilizers?

As plants grow, they absorb and deplete (or “mine”) nutrients from the soil. Farmers harvest those same nutrients when they harvest crops. Fertilizers, whether mineral or organic, nourish the soil by returning essential mineral nutrients.

It is a biological fact that plants require 1.0 kilogram (kg) of nitrogen to produce 10 to 15 kg of grain. Our atmosphere is about 80 percent nitrogen. Most tropical soils “fix,” or draw from the atmosphere, enough nitrogen to produce about 1 metric ton (mt) of grain per hectare. To produce more grain, the plants must have more nitrogen, whether from organic or mineral fertilizer sources. Plants must also have phosphorus, potassium and “trace” minerals. If a soil lacks or has insufficient amounts of these minerals, they must be added as fertilizers or production will stagnate or cease.

How have fertilizers benefited the world?

About half of the world’s population is alive today because of increased food production fueled by mineral fertilizers. Fertilizers and other inputs (improved seed and crop protection products) give the industrialized countries inexpensive food. For example, the average U.S. farm feeds about 150 Americans for a year, with a balance to export worldwide. U.S. citizens spend only about 10 cents of each dollar on food, so they have 90 cents for other things. Most rural families in Africa spend as much as three-fourths of their income on food. Little is left for necessities such as education of children and health care.

The Green Revolution – which generated dramatic increases in food production in Asia and Latin America – occurred because of higher crop yields. These yields were made possible through the use of improved seeds and inputs, particularly mineral fertilizers. The Green Revolution is credited with feeding more than one billion people in Asia alone. The far lower increases in food production in Africa have been gained primarily by bringing marginal land into production. That further threatens Africa’s endangered wildlife and ecosystems.

The late Nobel Laureate Dr. Norman Borlaug, often called the “father of the Green Revolution,” has called improved seeds the “catalysts that ignited the Green Revolution” and mineral fertilizer the “fuel” that powers it.

Isn’t it true that fertilizers can be detrimental to the environment?

Poor management of plant nutrients – whether as organic amendments or mineral fertilizers – can cause the loss of some nutrients to the environment, where they can upset the balance of natural ecosystems. Nitrogen may also volatilize – be lost as a greenhouse gas that affects the atmosphere. But if a farmer uses appropriate agricultural practices, the crop will absorb most applied fertilizer.

Using too few crop nutrients can also have devastating environmental effects. In the 1930s – before mineral fertilizers were widely used – nutrient depletion was widespread on many agricultural lands in North America. The result was the “Dust Bowl” era, with its extensive wind erosion and massive dust storms.

Africa today faces a soil fertility crisis. African soils are losing at least $4 billion worth of soil nutrients yearly. Three-fourths of the farmland in Sub-Saharan Africa is plagued by severe nutrient depletion, and 46 percent of the African continent suffers from desertification. African farmers desperately need mineral fertilizers to bring life back to the depleted soils, and to feed the continent’s inhabitants.

If production on existing farm land is not intensified, African farmers will continue to bring marginal land into production – a further threat to what remains of Africa’s precious wildlife and forests.

For more information on fertilizers, check out The Fertilizer Institute's initiative, Fertilizer 101.

Questions about African agriculture

Can Africa feed itself?

Agricultural production in Sub-Saharan Africa is hampered by low use of inputs such as improved seeds and mineral fertilizers, low inherent soil fertility on much of the continent and nutrient-depleted soils. Farmers have traditionally cleared land, grown a few crops and then moved on to clear more land, leaving the abandoned land fallow to regain its fertility. But a three percent annual growth in population – among the world’s highest – now forces farmers to grow crop after crop on the same land, “mining” or depleting mineral nutrients from the soil while giving nothing back, and to bring marginal land into production. Mineral fertilizers are the only practical way to restore plant nutrients and bring life to the severely depleted soils. But small-scale farmers, who comprise the vast majority of the farming population, have little access to fertilizers and can’t always afford them. The African farmer must pay two to four times the average world market price for fertilizers. Worsening the problem are weak input and output markets, unfavorable policies, corruption, poor transportation systems, limited irrigation and inadequate access to credit.

How does agriculture affect African economies?

Africa is a rural continent and agriculture is, by far, its most important economic sector. More than 70 percent of Africa’s population is directly engaged in agriculture. Sub-Saharan Africa (excluding South Africa) imported almost 20 million mt of cereal in 2004, at a cost of $4.4 billion. By 2020 Sub-Saharan Africa is projected to import more than 34 million mt yearly, at a cost of $8.5 billion, according to the U.N. Food and Agriculture Organization. On a positive note, cereal production has increased each year and in 2009, more than 14 million mt of cereals were produced in southern Africa. Slightly more than 3 million mt of cereals were imported to southern Africa in 2009, according to FAO’s Crop Prospects and Food Situation Report published in January 2010.

What are potential solutions to Africa’s agricultural crisis?

At the 2006 Africa Fertilizer Summit, former U.N. Secretary General Kofi Annan called for a “uniquely African” Green Revolution, similar to the one that revolutionized agricultural production in Asia and Latin America. In those areas, increased food production was made possible by improved seeds and other inputs, particularly fertilizer. High-yielding varieties of key African crops are available, but they can produce well only if nutrients are available in the soil to feed them. Farmers in Sub-Saharan Africa (excluding South Africa) today apply about 8.0 kg of fertilizer per hectare yearly. Fertilizer is essential to catalyze the new African Green Revolution by adding nutrients and organic matter to improve crop production and restore soil health. African farmers will use fertilizer, if they have access at an affordable price and if its use is profitable. This means ensuring fair prices for farm products.

Why are fertilizers so expensive in Africa?

It is a cruel irony that a farmer in Sub-Saharan Africa – where half the population survives, somehow, on less than $1.25 a day – must pay two to four times the average world price for fertilizer. This is mainly due to geography and poor infrastructure. Africa has few navigable waterways, so bulky goods such as fertilizers must be transported long distances overland on poorly maintained road and rail systems. Africa has the world’s fewest kilometers of paved roads per capita. For example, Uganda has 94 kilometers (km) of paved road per one million people and Mozambique, 141 km. In contrast, France has 12,987 km of paved road per million people and the United States has 20,987 km (as of 2006). Transporting fertilizers from an African seaport to a farm 100 km inland costs more than to ship those same fertilizers from North America to Africa. Also, the current low demand for fertilizer in Africa reduces potential economies of scale in procurement. Government policies, including those affecting tariffs and trade, often contribute to high prices. Corruption is another factor.


Workers unload bags of fertilizer from a ship at the port of Tema, Ghana. Most fertilizer used in Sub-Saharan Africa is imported.

Why not provide fertilizer free in Africa?

Sustainable growth in agricultural production requires the development of markets for both agricultural inputs and for farm products. In most African countries, less than a third of the food produced enters into commercial marketing channels beyond the local area. Also, it is often impossible for smallholder farmers to obtain reasonably priced farm inputs, such as fertilizer and improved seeds. Simply giving fertilizer away would do nothing to develop the market.

The alternative is for African governments to adopt policies and develop institutions that increase farmers’ purchasing power while also increasing access to farm inputs. For example, new financing arrangements could allow farmers to pool their resources, or make credit available at low risk, or that provide input vouchers (“smart” subsidies, rather than “blank checks”) to help farmers purchase fertilizer.

In the case of the poorest farmers who truly have no other options, it may make sense to begin by using market-friendly, targeted subsidies for fertilizer, together with advice on its efficient use, to jump-start a process of increased production and profits.