Garden & Greenhouse


The Importance of Micronutrients

Posted February 12th, 2015 by Garden & Greenhouse in ,

What is so important about micronutrients? Is it for a good healthy, high yielding vegetable crop or what? For each one there is only a small amount of each needed in the soil. So how can they play such an important role in crop production? Maybe it is time to look at them and see what each one’s role is.

A good soil test will show a total of 5 of them. In fact there are over 70 different micronutrients. At this time we are only interested in 5 of them found in a good soil test. If your soil-testing lab does not test for them on their test, you should consider switching labs. In fact it is equivalent of trying to build a building with only metal roofing, a hammer and some screws. It just does not work if you are baking a cake or constructing a building. Nor does it work if you are growing vegetables. You need to know what the levels of each of these micronutrients are in your soil.

It is a wise idea to stay with the same soil lab each year. Even though they may use the same equipment, each lab records them in a different form. For this reason you will potentially get different test results from the same soil sample.

Boron (B)Boron

Boron is an acid base anion (-) nutrient that doesn’t like excessive levels of N and K. This micronutrient also plays a very important role in moving calcium, sugars and phosphorus through the plants. Other important roles that Boron plays in the plants:

  • Calcium cannot perform its vital job of stabilizing the metabolism process without B. This can be one of the critical reasons tomatoes do not take up enough calcium to avoid blossom end rot.
  • Boron helps move sugars throughout the plants leading to a sweeter fruit or vegetable
  • It helps in aiding the plant’s resistance against harmful fungi and other diseases.
  • If you are looking for high seed production (high seed production = fruit) you need the correct level of Boron in the soil as it plays a very important part in this process.

Boron’s availability to a plant can decrease in heavy clay and high pH soils. Heavy applications of limestone can limit amounts of Boron for plant growth. Normally when base saturation of calcium is 89% it will start to limit B availability.

Copper (Cu)Copper

Copper is a weaker cation (+) held in the “Humus storehouse,” and exchangeability to the plant is dependent upon certain biological activity like mycorrhizae fungi. Copper especially accelerates root development. When Ca and K are in natural balance, plants can use Cu to build antibiotics for better disease control. Copper aids amino acid (protein) formation, which helps in nitrogen regulation within the plant. This is vital for the life/energy support system. High humus soil has adequate Cu. Copper’s enemies are high levels of potassium (K), iron and aluminum.

IronIron (Fe)

Iron is also a cation (+) that is needed in very small amounts in a plant. Iron is a vital carrier of oxygen for photosynthesis in all plants. Iron is an enzyme activator. If there is an iron deficiency in a growing plant, look for a low pH soil and excessive levels of N, KCI or sodium.

Manganese (Mn)Manganese

Manganese is a weaker cation held in the “humus storehouse.” Manganese aids in carrying oxygen and sugar throughout the plant in complex with other nutrients. High pH combined with high organic matter can create Mn deficiency. A low sulphur level can nearly stop the flow of Mn to plants. Flooding and soil compaction will decrease Mn exchangeability. Working the soil when it is wet will reduce the availability of N, P, S, Mn and others. Manganese is a part of the complete amino acid complex, which is necessary in all healthy animal diets.

Manganese is essential for a high-energy seed for quicker emergence. It helps activate the calcium/phosphorus energy systems of a seed and plant. Manganese determines the “shortest” time from bloom set to harvest maturity.

High pH soils above 6.9 can become a problem in Mn availability. This is why it is preferable to see a natural balance pH consisting of 6-10% hydrogen. This natural acid allows nutrients such as Mn to flow to the pant.

Zinc (Zn)Zinc

Zinc is a necessary part of certain plant enzymes called dehydrogenates that are vital in the metabolic functions of cellular respiration. A zinc deficient plant will have limited cell functions and will not be a normal healthy plant. Zinc aids in better cellular metabolism and the regulation of CO2 and O2 in and out of a plant. It also helps regulate the pH of the cell sap, which is vital in times of stress.

There may be plenty of zinc in the mineral makeup of the soil, but it may not be available to the plant because of too much K or N. Exchangeable Zn is absorbed through roots as ZnO4 (this decreases sharply with ammonium N). Zinc’s availability can be a problem as soil pH increases in light, sandy soils and under cool, wet weather conditions.

It is amazing how many growers think that if a little does good, a lot more will do better yet. This is wrong. For instance, too much Boron and your plants will die. All nutrients have a limit of how much can be applied to the soil before they become toxic.

Norman Kilmer is the president of Morgan County Seeds and can be contacted at 573.378.2655 or

Want more information? Try these articles:

Building Your Own Organic Soil for Raised Bed Gardens

Iron (Fe): The Fussy Micronutrient Element

Is There a Universal Nutrient Solution Formulation?

Making Hydroponic Systems Efficient in Water and Reagent Use

Requirements for Successful Soil-Based Vegetable Gardening

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