Why do plants need fertilizers?

To grow healthy crops full of nutrients, farmers need to ensure they have healthy soil. Without fertilizers, nature struggles to replenish the nutrients in the soil.

fertilizer application
fertilizer application

When crops are harvested, important nutrients are removed from the soil, because they follow the crop and end up at the dinner table. If the soil is not replenished with nutrients through fertilizing, crop yields will deteriorate over time.

Careful analyzing and fertilizing of crops enables a chain that provides humans with nutritional food:

  • The nutrients feed the soil
  • The soil feeds the plants
  • Plants feed animals and people

The three most common mineral fertilizers are those based on nitrogen, phosphorus and potassium.

The International Fertilizer Association (IFA) estimate that 85% of the soils globally are deficient in nitrogen(1). Seventy-three percent of the soils are deficient in phosphorus, whereas 55% lack potassium.

What is fertilizer used for?

Research trials

Often, the plants have few possibilities to avoid nutrient deficiencies without the help of fertilizers.

Take nitrogen for example: Since plants are not capable of absorbing it from the air directly, the soil is their only means of acquiring this important nutrient. If the soil is low on nitrogen, fertilizers are needed to boost nutritional levels.

Large concentrations of potassium sources occur deep below the soil surface (often around one kilometer) and are far beyond the reach of plant roots. Mining of potassium brings this naturally occurring nutrient to the soil surface and within the grasp of plant roots. 

Phosphorus exists in certain rocks, but for plants to access this nutrient, it needs to be water soluble. The correct use of phosphorus fertilizers helps plants absorb it through the soil and ensures a high production and rapid growth. 

What is the difference between mineral fertilizers and organic fertilizers?

In nature there are 17 nutrients necessary for plants to thrive. What kind of fertilizer you need, depends on what crop you grow and the nutrient deficits in each specific soil. Different crops remove different amounts of nutrients from the soil.

Many farmers use NPK compound fertilizers that provide a combination of several nutrients at the same time.

Organic fertilizers such as animal waste and compost have been used for centuries and are a valuable source of nutrients and organic matter, which enhances soil structure.

But since the 20th century, mineral fertilizers have been required to meet the increasing food requirements of a growing world population. The amounts of nutrients in organic fertilizers vary and are much less concentrated than those in mineral fertilizers.

Mineral fertilizers reduce the amount needed and the number of vehicles to transport the fertilizing products.

By 2050, the global population is estimated to reach 9.8 billion, according to the United Nations(2). Increasing crop yields is essential if we are going to be able to produce enough food for everyone.

This increase is not possible without carefully planned fertilizing.

What are the benefits of fertilizers?

Knowing the exact amounts of nutrients in the mineral fertilizer also makes it easier to plan the farming process. Fertilizers containing major, secondary and micronutrients are now more widely available to farmers.

Mineral fertilizers mostly come in a convenient solid granular form, which makes them well suited to transport and application by the farmer. Plants that grow in nutritionally deficient and unfertilized soil will often be smaller and grow slower than plants from healthy soil. 

Why are nutrients important to humans?

When we eat wheat, apples, potatoes or other plants, the nutrients from the fertilized soil is transferred to our bodies. The same happens if we eat animals who have eaten plants with the same nutrients.cows graze in a field

For example, milk is a good supply of calcium, which prevents us from developing weak and brittle bones.

But the milk will not contain as much calcium if the cows do not graze on fields with enough of this nutrient in the soil.

Growing food in soil with a good balance of nutrients is therefore key to preventing malnourishment. It also prevents illnesses related to deficiencies in populations across the world.

One example is Finland, where the government has mandated the addition of selenium to all multi-nutrient fertilizers since 1984. In this way, they have managed to combat heart disease in the population with great success. 

External resources: 

1 - Infographic - Fertilizing crops to improve human health (pdf, 0.2 MB) 

2 - World Population Prospects 2017 - United Nations