The Importance of Nutrients                                                


What nutrients do Crops need and when do they need them?


Crop nutrition is crucial to the healthy life cycle of any crop. Just like a human diet of 5 major food groups for healthy nutrition, a plant needs a staple diet of 16 essential elements in a complete and total nutrient program to produce any crop. Carbon, hydrogen, oxygen and some nitrogen come from air and water. Remaining Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulphur, Zinc, Boron, Manganese, Copper, Iron, Molybdenum and Chloride come from the soil and fertiliser.

To understand the importance of good crop nutrition, it is important to realise that all nutrients are important throughout a growing season. However, there are critical stages of growth when the lack of specific nutrients will be a limiting factor in a plant’s growth and final yield.

12 of the soil or foliar applied nutrients and their period of most critical need in the growing of a plant is summarised in the table below:

0-40 days after planting

Rapid Growth Period

Fruiting Period or Reproduction




















Early nutrient needs for an established crop.

After planting, the root system of a newly established crop must seek out nutrients within the soil. One of the main reasons that these nutrients are critical during this stage is that they are not mobile within the soil's water and instead remain stationary. The root system must go after these nutrients as they do not flow with the water to the root system. In a young plant, however, it is not able to get hold of slow-moving nutrients because the roots become saturated with the accessibility of other mobile elements such as potassium, calcium or sodium which show high levels within the soil. Therefore, the closer you place the non-mobile nutrient to the seed, the more response you will get from the dollar invested in these nutrients. The preferred method to do this is to apply the nutrients to the seed at planting (in-furrow application) or to foliar spray the established crop at the 3 to 4 leaf stage.

Non-Mobile Nutrients


Zinc is essential for plants in seed and grain formation and for achieving high yields. It is particularly important in the maturation date of plants, in the height of plants and in protein synthesis. Zinc deficiency is one of the easiest to diagnose- either visually or by soil or tissue testing, it is also the easiest to correct. Deficiency if present can cause short internodes and stunted youngers leaves.


The most important function of iron in a plant is to promote the formation of chlorophyll, the green pigment of a plant which functions in photosynthesis or starch production. It is also the enzyme mechanism which operates the respiratory system of living cells and has a reaction involving cell division and growth. Iron is not readily translocated from old to new leaves, so a constantly available source is needed during the entire growing season. Iron is found abundantly in most soils, but mostly in a form which is unavailable to the plant. Deficiency causes interveinal yellowing and/or death of younger leaves. 


Magnesium participates in the activity of enzymes, assists in translocation of phosphorus in the plant, and is found mostly in the chlorophyll-bearing tissues in the plant. It is critical for photosynthesis and helps the plants metabolic process. Deficiency causes interveinal yellowing and a striped look on older leaves.


Manganese is the predominant metal ion in the metabolism of organic acids. And, in higher plants, manganese activates the reduction of nitrate and hydroxylamine to ammonia. It is a part of the important enzymes involved in respiration and protein synthesis. It generally serves as an activator for a variety of enzyme reactions such as oxidation, reduction, hydrolysis and group transfer. Manganese has a particular interest as it relates to photosynthesis. It may have a direct or indirect influence on the chloroplast - the location of the conversion of sunlight energy to chemical energy. Deficiency causes interveinal yellowing on younger leaves.


Copper's function in plant growth cannot be replaced by any other element, as copper is an enzyme activator and becomes a component of certain enzymes that function in respiration and in photosynthesis. Deficiency can result in a blue-green tinge on leaves that lead to yellowing and curling.


Mobile Nutrients-Rapid Growth Period

Nitrogen and Potassium

Nitrogen is essential to healthy plant growth and used in chlorophyll and photosynthesis Deficiency of nitrogen can cause stunting and yellowing in older leaves. The application of potassium is essential to reproduction and fruit quality including size, shape, colour, taste and shelf life.


Sulphur is used in photosynthesis and formation of plant proteins as well as enzyme activity. A rule of thumb for sulphur in the plant is 1-part sulphur for every 10-12 parts of nitrogen. Without sulphur, the plant cannot use its nitrogen- 1 to ·12 is about the chemical ratio of protein in the plant.


Moly is the other plant nutrient that is necessary for the plant to convert its nitrogen to protein. Molybdenum is part of the enzyme within a plant that will change nitrate to protein. This enzyme known as nitrate reductase has one of the most important functions in the plant's growth. Deficiency can cause general yellowing, stunting and scorching or cupping of leaf edges.

Nutrients essential to the fruiting period and reproductive period

Calcium and Boron

Calcium and Boron are critical nutrients to a crop during the fruiting and reproductive period. Basically, what calcium in the leaf does is cut down on the respiration. A plant does two things: Inhale carbon dioxide and exhale oxygen- a process called photosynthesis which produces sugars and starches. However, when the plant's nervous energy gets up to a top peak, it starts breaking down the sugars and starches in the leaf and starts exhaling carbon dioxide, which is the very thing the plant should be taking in. This is called respiration. Therefore, calcium controls the respiration, or the loss of carbon dioxide, or sugars or starches. Boron controls the movement of these sugars and starches from the leaf to the fruit.

Calcium is critical for plant cell wall production and is important for root and leaf growth as well as nutrient uptake. Often the question is asked, “Why should a soil that is high in calcium ever grow calcium deficient plants?” The answer is rather simply. For, as a plant grows, it needs a constant supply of calcium. It does not build up calcium; the plant takes the calcium up and out of the branches to the leaves. During a dry spell where there are nights of low humidity, and dry hot days, there is excessive evaporation. The calcium in the soil is taken up by the root system and goes up to the top part of the plant where evaporation occurs- the same place where the calcium will collect in the plant, at the top.

If calcium deficiency occurs in a plant, it is like cancer. It is a runaway destruction of the plant's cells. Once this condition exists, it takes massive doses by drenching to cure or stop cancer called “calcium deficiency.” With the small doses of calcium foliar applied, one can prevent cancer from starting. It is a condition easier to prevent than to stop.

Boron is also important in cell wall production but also used in the production of sugars and proteins. It is also important in flowers, pollen, seed and fruit development. A deficiency can cause the death of younger leaves and stunting can occur.


The effect of balanced crop nutrition

A balanced program of adequate crop nutrition throughout your crops season can work towards improving crop yield and quality as well as set you up for a successful next season. In Summary, phosphorus, zinc, iron, manganese, copper, and magnesium are of the utmost importance in the first 40 days of the plant's life. That nitrogen, potassium, sulphur and molybdenum are rapid growth elements. Calcium and Boron are the fruiting, or reproductive elements of greater importance. The greatest tool for the success of your farm is soil and tissue testing analysis to be used as guides for a balanced fertiliser program.

Talk to your Stoller representative today for effective soil and tissue analysis and how we can maximise the genetic potential of your crop.