By Brad Haire
University of Georgia
Farm crops worldwide have a tough time getting enough phosphorus
for healthy growth. An international guest scientist at the
University of Georgia is looking to solve this problem with a
common food item.
To grow, plants pull elements from the soil through their roots.
Phosphorus is one of the hardest elements for their roots to
soak up, especially in acidic tropical and subtropical clay
soils, like those of Georgia and Kenya.
This is due to chemistry and how phosphorus interacts with other
elements in the soil, said Charles Gerroh, a soil scientist from
Kenya conducting research at the UGA College of Agricultural and
Environmental Science campus in Tifton, Ga.
Common concern
“Phosphorus availability to plants is considered a major soil
fertility problem around the world,” he said.
Gerroh is head of the horticulture department at Maseno
University in Kenya and a Fulbright scholar working with Gary
Gascho, a UGA CAES crop and soil scientist.
The Fulbright grant program was established in 1946. Sponsored
by the U.S. State Department, its mission is to increase
understanding between the United States and other countries
through the exchange of people, knowledge and skills.
Phosphorus, Gerroh said, is essential for healthy plant growth,
especially when the plant is young. Phosphorus helps roots
develop and gives a plant a good head start.
It’s one of the three major fertility elements, along with
nitrogen and potassium. Depending on conditions, it’s the most
expensive fertilizer element farmers apply.
Fixed
The study of soil fertility can be complicated. But to put the
phosphorus problem simply, it doesn’t move through the soil as
other elements do.
Phosphorus can become fixed in a form that’s not easily
accessible to plants. If it’s not applied directly around a
plant’s root area, the plant has little chance of getting it
into its system.
“Only about 5 to 10 percent of the phosphorus in low-pH soil is
able to be used by plants,” Gerroh said. Plants can access and
use 50 percent to 60 percent of the nitrogen applied in the
soil.
But another element, silicon, holds the answer, Gerroh said.
Silicon can interact in the soil to make phosphorus more
available to a plant.
Unfixed
Using silicon this way is nothing new, he said. Several Asian
countries are doing it. The difference is Gerroh’s silicon
comes from rice.
Rice hulls, generally considered trash after rice processing,
have a large concentration of silicon. Gerroh is working to find
the best way to get and apply this form of silicon as a soil
amendment to fix, or unfix, the phosphorus fertility problem.
Gascho has worked in the Southeast using silicon as a potential
solution to the fertility problems here. This is one reason the
two soil scientists have joined forces through the Fulbright
program.
