Nickel

If I had a nickel for every time something went wrong in the garden…

But, wait! The truth is, if I had a nickel for every time something went well in the garden, well, I’d be a rich woman.

Talking about nickels, did you know that nickel is a plant nutrient? Let’s find out what it does.

Branches of nickel-sufficient (left) and nickel-deficient (right) pecan plants (Bruce Wood, USDA-ARS) Public Domain

Plant nutrients

Most of us who play in the garden are familiar with the Big Three of plant nutrition: nitrogen, phosphorus, and potassium. These are the NPK of fertilizer fame, respectively. They are called macronutrients because plants use them in relatively large quantities. You might consider them the meat and potatoes of a plant’s diet. Following the macronutrients in quantity consumed and importance to plant health are the secondary nutrients of calcium, magnesium, and sulfur. These are the side dishes.

Just as any meal would be bland and unsatisfying without seasonings and little surprises, a plant’s diet must also include several micronutrients: boron, chlorine, cobalt, copper, iron, manganese, molybdenum, selenium, silicon, sodium, vanadium, zinc, and nickel.

Now, nickel (Ni) wasn’t recognized as a plant nutrient until late in the game. In 1987, one group tried to sponsor nickel into the plant food arena, but it wasn’t until 2004 that the American Association of Plant Food Control recognized nickel as an essential element. [I’ll bet you didn’t know that was a group – I sure didn’t.] It ends up that nickel is used in such small quantities that we didn’t have the technology to measure it properly until the mid-1970s. California still refuses to acknowledge nickel as a plant nutrient. I have no idea why.

Nickel deficiency of soybean (David Eskew and Colin Walker, USDA) Public Domain

Orders of plants

Before we learn how plants use nickel, we need to understand the difference between higher and lower order plants. Lower-order plants do not have vascular bundles. These are the algae, hornworts, liverworts, and mosses. Higher-order plants have veins. This ginormous group includes ferns, gymnosperms (including conifers), and flowering plants (angiosperms). Now that we’ve cleared that up, we can learn how they use nickel.

How plants use nickel

In vascular plants, nickel is an extremely important puzzle piece that unlocks the ability to metabolize and fix nitrogen. It is also used to help plants process urea. Urea is commonly used as a source of nitrogen. Too much urea in a plant can cause necrotic lesions [read ugly, weeping sores]. Nickel helps convert urea into ammonia (NH3), which plants can then use as a nitrogen source.

In lower order plants, nickel is used to activate enzymes in several different processes. These more primitive plants can often use nickel in place of iron and zinc.

In legumes, nickel is a major player in the development of root nodules used to fix atmospheric nitrogen into a form plants can use. Nickel is also very important to pecan trees. And plants are more likely to get sick when they don’t have enough nickel.

Speaking of plant diseases, nickel has been found to help prevent several of them. Scientists aren’t sure if this is because nickel stimulates the plant to defend itself or if the nickel acts directly on the pathogen, but it is important. Research has found that nickel applications reduced cowpea fungal diseases of leaves by 50%. That’s huge!

Nickel deficient cowpea on the right (David Eskew and Colin Walker, USDA) Public Domain

Signs of nickel deficiency

Leaf tip death is the earliest sign of a nickel deficiency. Nickel-deficient pecan trees develop “mouse-eared” leaves, bud break is delayed, and bronzing, chlorosis and leaf tip death are common. [Mouse-eared leaves are smaller than normal and curled.]

This damage can be reversed with the application of a dilute nickel solution. Before you go around painting leaves with nickel water, you need to know that these deficiencies are extremely rare. So rare, in fact, that nickel isn’t included in most soil tests (unless you want to pay extra). That being said, soils low in nickel can be found in the southeastern United States and parts of England. These soils also tend to be low in manganese and zinc. Adding nickel in these cases has been shown to significantly improve bean, potato, and wheat crops.

Nickel is a mobile plant nutrient, which means it moves around within the plant freely, going to wherever it is needed.

There you have it. You now know more about nickel in plants than pretty much everyone you know.