Researchers Studying If Soil Amendments Can Lower Fragipan Depth
LEXINGTON, KY.
A fragipan is a cement-like layer found in
some soils. Soils containing this layer are
common throughout the major crop production
areas of Kentucky, and they limit grain
crops’ yield potential, especially during dry seasons.
University of Kentucky College of Agriculture
soil scientist John Grove is conducting a
study that will look at potential ways to move
the fragipan layer deeper in the soil profile and
increase corn and soybean yields.
“Many of the fragipan soils in Kentucky are
rated by the Natural Resources Conservation
Service as Class II or III soils and only about
two-thirds of them are being actively farmed or
pastured,” Grove said. “My vision for this study
is that we will learn a way to add value to the
soil and help growers move their ground to a
higher level of productivity.”
About 250,000 acres of Kentucky soybeans
are on grown on fragipan soils. The fragipan affects
crop yields by causing excessive moisture
during wet periods in the spring. This can delay
planting or result in compaction caused by
“mudding in” a crop. In addition, fragipan soils
increase the probability that the plant will experience
drought stress during dry periods that
are normally experienced during a Kentucky
summer. Fragipan restricts plant root growth,
and roots cannot reach available water deeper
in the soil. In addition, Kentucky’s fragipan subsoils
are often acidic, which can further restrict
plant root growth and water uptake.
In a study funded by the Kentucky Soybean
Promotion Board, Grove and fellow UK soil scientist
Edwin Ritchey conducted small-plot research
in 2012 to determine if the addition of
either gypsum or poultry litter or both could
lower the fragipan depth and increase corn and
soybean production.
Previous studies in other countries have
shown gypsum can reduce the effects of acidic
soil on corn crops. In an unrelated study at the
UK Research and Education Center in Princeton,
researchers made a chance observation
that poultry litter might increase the depth of
the fragipan in the soil profile.
Grove and Ritchey’s 2012 study occurred on
128 plots (64 plots for each crop) at the UK Research
and Education Center at Princeton on a
Sadler silt loam with a fragipan. They amended
crop-specific plots with 16 replications each of 3
tons of gypsum, 3 tons of poultry litter, both or
neither. They will repeat the study during the
2013 growing season.
In the 2012 study, soybean plots that received
poultry litter only and plots with poultry litter
and gypsum yielded two more bushels per acre
than plots without either amendment or only
gypsum. Grove noted that because the 2012
drought was so severe, there was not a significant
amount of moisture to move the gypsum
and/or soluble poultry litter constituents
deeper into the soil. When the amendments
move deeper in the soil, greater yield returns are
expected.
“We know from studies in Brazil and Africa
that if you’re going to see any benefit from gypsum,
it should appear by the second year,”
Grove said. “We’re hoping rain this winter will
help move the soluble constituents deeper into
the soil so that we can see benefits from gypsum
this year.”
If the amendments cause the fragipan to move
deeper into the soil, researchers hope to learn if
the movement is caused by the fragipan actually
dissolving or dissolving and reforming at a
deeper depth. Δ
Small plot work will give researchers an idea of whether gypsum,
poultry litter or both can improve grain yields.
PHOTO: John Grove, UK soil scientist