Understanding The Makeup Of Fertilizer – Part 3

Understanding The Makeup Of Fertilizer – Part 3 – Mg, Mn, Cu, B, Mo, and Zn



At the top of almost all fertilizer labels, there is a list of the nutrients and their percentages. This is known as a “Guaranteed Analysis”. The guaranteed analysis is a legal claim of what % components make up each prill of the fertilizer contained within this bag. Refer to this list to determine if this is the right product for your crop


This is part 3, the final installment of our series, and we are going to cover the remainder of the micronutrients on the label. These nutrients help take your crops that much further.

We will be covering Magnesium (Mg), Manganese (Mn), Copper (Cu), Boron (B), Molybdenum (Mo), and Zinc (Zn)



Magnesium (Mg)

Magnesium drives photosynthesis in plants. Without magnesium, chlorophyll cannot capture the energy needed for photosynthesis. In short, magnesium is required to give leaves their green color. Magnesium in plants is located in the enzymes, in the heart of the chlorophyll molecule. Magnesium is also used by plants for the metabolism of carbohydrates and in cell membrane stabilization.


Signs of Magnesium Deficiency

• Yellowing between the leaf veins,

• Reddish-brown color on the leaf edge

• Premature leaf fall




Manganese (Mn) Manganese is a fascinating and powerful element in plants. In photosynthesis, it helps process, water, and CO2 (with the addition of light) down into a digestible carbohydrate for the plant. Think of it like lighter fluid for a fire; a small amount of it is necessary to assist it in getting going, but if you put too much of it on the fire, you’ll get a violent explosion. This is roughly the same concept with Manganese.


Plants need a small amount to “jump-start” photosynthesis (and aid other metabolic processes) but too much leads to a toxic state. Signs of Manganese Deficiency (may appear as Iron deficiency) • Yellow leaves with green veins • Tan and brown spots on leaves • Stunted growth


Signs of Manganese Toxicity (too much Manganese) • Veins turn dark colors (usually black) • Leaf curling or cupping



Copper (Cu) Copper (Cu) activates some enzymes in plants that are involved in the strengthening of the plant's cell walls. It is also required in the process of photosynthesis, is essential in plant respiration, and assists in plant metabolism of carbohydrates and proteins. Copper also serves to intensify flavor and color in vegetables and color in flowers.



Signs of Copper Deficiency • Newest leaves will have yellow or brown spots • Newest leaves will grow stunted, or small • Newest leaves will come in curled




Boron (B) Boron (B) is a micronutrient critical to the growth and health of all crops. It is a component of plant cell walls and reproductive structures. Boron, just like Manganese is only needed in small amounts, so it is important that it be applied evenly throughout the soil.


Signs of Boron Deficiency: • Empty pollen grains & poor pollen vitality • Reduced number of flowers per plant • Stunted root growth

• Stunted development


However, like with Manganese, we have to talk about the signs of Boron toxicity. Which are: • Yellowing or browning of foliage • Drying out of leaf tips (that may spread leaf wide) • Some plants may ooze a gummy substance from the branches or trunk • Stunted growth • Low production in fruiting plants



Molybdenum (Mo) Molybdenum functions as an essential catalyst for two enzymes that are essential for plant health. These enzymes assist in a process called nitrogen “fixing” which is a process by which the plant converts a non-available source of nitrogen into one that is easily useable (Nitrate to Ammoniacal). Similar to how the human body breaks down food into useable energy in its intestines.


Signs of Molybdenum Deficiency: Rather than a list here, a description is better, as, without Molybdenum working, a plant does not receive the proper amount of Nitrogen. So if you are fertilizing your plants with adequate N, and they are not seeing the benefits of it, a Molybdenum deficiency may be to blame.


Molybdenum Toxicity This is not as common as Manganese or Boron toxicity, however, it can happen, and will appear as a Copper deficiency, as the fringes of the leaves will begin to have a golden appearance.




Zinc (Zn) Zinc (Zn) is an integral part of various enzymes throughout the plant that synthesizes proteins. These proteins assist in forming chlorophyll and carbohydrates. Zinc also assists the plant in surviving cold temperatures. Zinc also assists in plant growth regulation.




Signs of Zinc Deficiency (new growth) • Chlorosis of the new leaves • Necrotic spots on the margins or leaf tips • Poor bud development • Reduced flowering and branching