Vanadium: Nature's "Junk Food" For Plants

By Don Comis
June 16, 1999

MORRIS, Minn., June 16--Gardeners and farmers who are used to checking the N-P-K (nitrogen-phosphorus-potassium) levels on their fertilizer bags may someday be checking N-P-K-V levels in their soil. That's V for vanadium.

Vanadium "impersonates" phosphorus and can confuse a plant into eating it instead of phosphorus. That can cause the plant to experience a phenomenon akin to that of people who eat junk food in place of a nutritious meal, reports soil scientist Alan F. Olness with the USDA's Agricultural Research Service.

"The hunger goes away but the nutrients never arrive," said Olness, with ARS' North Central Soil Conservation Research Laboratory in Morris, Minn. "Phosphorus is an essential nutrient plants need for growth. But vanadium, a trace element abundant in soils throughout the world, is useless to many plants, including corn, soybean, tomatoes, Impatiens and petunias."

Olness plans to study different soil types this summer to see if there is any relationship between soil type and high vanadium content.

"During a growing season," he said, "plants may have only two or three time windows during which they can take in phosphorus. If they fill up on vanadium instead, they miss out on phosphorus, because their root cells can't tell them apart. Their growth and development--and yields--suffer. The more vanadium, the more the plant slows down and the lower the yield. For ornamentals, the slowdown could result in less beauty and hardiness."

Vanadium captured Olness' interest about a decade ago, when he discovered that it mysteriously reduces soybean yields.

"Studying the vanadium effect has been some of the most exciting work of my career," said Olness, who has worked as an ARS soil scientist for 32 years.

In the past 3 years, he and colleagues have confirmed earlier work showing that plants do confuse this little-known soil trace element with phosphorus.

Plants may not be the only organisms misled by vanadium. "Vanadium may be the missing element causing lapses in the accuracy of soil phosphorus recommendations given to farmers and gardeners," Olness said.

Standard soil tests don't measure vanadium. Ten years ago, Olness developed a test that does. It also measures the ratio of vanadium to soil phosphorus and other nutrients. Olness said this test could be used to recalculate phosphorus recommendations. The optimum economic amounts of phosphorus would have to be re-determined through research. Scientists would have to consider the soil's ratio of vanadium to phosphorus when they correlate phosphorus concentrations with plant growth.

"This could lead to higher phosphorus recommendations in soils that are very high in vanadium--probably over 150 parts per million," Olness said. "But it could also lower phosphorus recommendations in soils with low levels, perhaps under 100 ppm.

"And the test can identify soils so high in vanadium that it wouldn't be economical to add the high levels of phosphorus required to boost yields. In that case, the farmer or gardener might want to switch to a crop that needs less phosphorus or a crop variety that blocks or neutralizes vanadium within the plant."

There's even hope for the vanadium-befuddled soybean, according to Olness. "We know vanadium 'immunity' can be bred into plants, because we found a soybean variety that is rather unaffected by vanadium. This provides us with hope we can extend the ability of this variety to other crops. One of the next steps is to determine how this variety is controlling vanadium."

He plans to expand his soil testing to other states in the Mississippi River Valley. He also plans to develop a phosphorus advisory so farmers can account for the vanadium effect.

Scientific contact: Alan E. Olness, ARS North Central Soil Conservation Research Laboratory, Morris, Minn., phone (320) 589-3411, fax (320) 589-3787, aolness@mail.mrsars.usda.gov.