Copper Roles in Plant Health

May 1, 2023

Copper is known far and wide for its importance in disease control, and rightfully so, because it has a tremendous impact on stimulating plants natural resistance to pests and disease. However, regenerative farmers recognize that it is more important to get copper into the leaf than unto the leaf.

However, copper is only one mineral, and it is important to recognize that copper interacts with other minerals. For example, copper has major interactions with nitrogen. Whenever nitrogen applications are high, it also takes more copper for optimal plant health, even if that nitrogen is coming from amino acids. Otherwise, it is possible for those plants to start showing copper deficiency and pale yellow new leaves. This, of course, will also mean that the plants will produce less sugars and carbohydrates, and have lower brix content.

In addition to influencing sugar production, copper also activates several enzymes that influence carbohydrate and nitrogen metabolism. In other words, copper influences how these sugars that are produced through photosynthesis are complexed into advanced, more complete forms of sugar. And copper also influences nitrate metabolism into complete proteins. Or we could say it more directly: when plants are copper deficient, nitrates are not converted into complete proteins and thus we have more problems with insect pests.

Copper also has an interesting effect on plant cell structures. Copper deficient leaves will be weaker and tend to hang down. Plants that have adequate levels of copper will be stronger but also flexible, allowing them to bend over in wind and rain, yet stand erect again after the storm. In addition, it also makes the cell walls more elastic, enhancing resistance to cracking. This is very helpful in crops such as tomatoes and onions.

In addition to leaf color, copper also impacts leaf expression. When copper is deficient, leaves and petioles tend to become brittle and twisted.

Copper, along with manganese and boron, are also very important for pollination. Plants will not pollinate properly when these minerals are too deficient. An example is cherries: it is not uncommon for cherries trees to bloom tremendously, and even appear to set a lot of fruit, but with time the fruit will fall off, called June-drop, as a result of improper pollination.

I mentioned that copper needs to be applied in higher rates when nitrogen is over-applied. But copper can also be over-applied. Excessive copper will deplete molybdenum, and vise-versa. We have also seen zinc deficiency as a result of excessive copper fungicide applications.

In summary, copper, like all minerals, is important, but it is more important to balance all nutrients so that plant health can be optimized.