Why do we need fertilizers?

Crops require a balanced diet of essential nutrients throughout their growth cycle.

Many of these essential nutrients can be found in the soil, but often in insufficient quantities to sustain high crop yields. Soil and climatic conditions can also limit a plant’s uptake of nutrients at key growth stages.
Plants need 13 essential minerals, all of which play a number of important functions. If any of these is lacking, plant growth and yield suffer. Farmers can turn to Yara for help.

Crop Needs

Each crop needs a different range of nutrients at every critical stage of its development.

For example, nitrogen and phosphorous are often more critical at early stages of growth to fuel root and leaf development, whereas zinc and boron are important during flowering.

Cereal crops use nutrients for growth, progressively moving them from the roots, leaves and stems into the ear prior to the dying off and harvesting of the grain.

Tree crops have different nutrient requirements than field crops. They can store nutrients like nitrogen within their trunk, branches and leaves and then redistribute them at key points during the growth cycle.  It is important, however, to supply trees with replacement levels of the nutrients removed in the harvested fruit and those that are critical for growth but can’t be recycled.

High-value, high-quality greenhouse crops have perhaps the greatest need for nutritional precision. Top- quality strawberries, lettuce or fruit require a constant and accurately balanced diet. Growers therefore often control crop growth by spoon-feeding plants with what they need in an environment protected from the changing soil and weather conditions.

In all situations, it is important that fertilizer formulation and selection matches the crop’s needs. We at Yara have an established and highly successful range of crop nutrition management programs that do just that.

Armed with this information and the right Yara product, the grower can ensure nutrient needs are met and growth and crop quality is maximized.  This provides high yields and high profits from the use of high-quality fertilizers.

Major Nutrients

Of the major nutrients, nitrogen (N) is often required in the greatest quantity by crops, primarily for vigor and yield. Nitrogen plays a key role in chlorophyll production and protein synthesis. Chlorophyll is the green plant pigment responsible for photosynthesis. When nitrogen is deficient, plants develop yellow or pale leaves and their growth is stunted.

Phosphorus (P), is a vital component of adenosine triphosphate (ATP) which supplies the energy for many processes in the plant.  Phosphorus rarely produces spectacular growth responses, but is fundamental to the successful development of all crops. For example, maize or other corn crops that lack phosphorus during the growing season achieve lower yields.

Potassium (K) is needed by virtually all crops and often in higher rates than nitrogen. Potassium regulates the plant’s water content and expansion. It is key to achieving good yield and quality in cotton and critical for increasing the size, juice content and sweetness of fruit.

Secondary Nutrients

Of the three secondary nutrients needed at lower levels than nitrogen, phosphorus and potassium (NPK), calcium (Ca) is perhaps the most important. Calcium strengthens cell walls, helping to reduce bruising and disease in fruit, salad and vegetable crops. This means that a good supply of calcium produces food crops that are less prone to damage and have a longer shelf life. Crops short in calcium will have growth disorders such as corky skin.

Fruit and vegetables containing higher levels of calcium also have a higher nutritional value – for example, vitamin C and antioxidants in tomatoes. This means that eating fresh fruit with strong skins and a great, crisp bite will help provide us with the calcium we need for strong bones.

Magnesium (Mg) is also important for crop quality, but is also a key component of leaf chlorophyll and the enzymes that support plant growth. Low magnesium leads to reduced photosynthesis, which severely limits crop yields.

Grain fill in rice and dry matter content of potatoes can be significantly reduced if magnesium is undersupplied.

Sulfur (S) is an essential part of many amino acids and proteins. Without both S and Mg, crops suffer; growth slows and leaves turn pale or yellow. Sulfur is particularly important for ensuring the protein content of cereal crop grains.


Micronutrients reinforce and supplement the strong plant growth and structures provided by major and secondary nutrients.

Most micronutrients influence growth.  For example, manganese (Mn), iron (Fe) and copper (Cu) all influence photosynthesis, the process whereby plants use sunlight for growth. 

  • Iron deficiencies are common – for example in seed fruits – where the effect is to reduce production of chlorophyll.  As a result, crops struggle and younger leaves develop a severe yellowing or chlorosis. 
  • Boron (B) is needed for the development of shoots and roots, and is essential during the flowering and fruiting phases of crops.
  • Zinc (Zn) is needed for the production of important plant hormones, like auxin. Zinc deficiency leads to structural defects in leaves and other plant organs.
  • Molybdenum (Mo) is involved in plant enzyme systems that control nitrogen metabolism.