“We should think of
Texas as being in continual drought broken by periods of rain” –Unknown
As I begin writing this article, I’m looking out my window
on the Texas A&M campus and see rain falling steadily. In fact, over the last 3 weeks, we’ve had
around 13 inches of rain fall here in College Station. Surely after such monsoonal-type weather the
drought has to be over, right?
According to the latest drought
map, 90% of the state is still experiencing drought conditions, with almost
22% in the severe to exceptional categories (Read about drought categories at U.S.
Drought Monitor Classification Scheme). In fact, Texas has not emerged from
the current drought spell which began in late 2010 with 2011 being the driest
year on record in Texas. Sure, the
wet weather we’ve been experiencing lately has been a true blessing and has
helped with soil moisture conditions, but what about our state’s water
supplies? According to a Texas Water
Development Board website, our state’s reservoirs are currently at 60%
full, which is close to an all-time record low (see map below), and groundwater
conditions across the state are not much better.
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| Reservoir conditions as of October 18, 2013. Colors correspond to percentages on the left for reservoir levels. |
In August of 2011,
Dr. Jim Cathey wrote an article called It
Will Rain Again… Maybe, where he described how the drought was affecting
wildlife in the state. Let’s examine
what happens to land when it is devastated by drought. When livestock stocking rates are not
adjusted properly to drought conditions, overgrazing can occur and results in
bare ground. Lack of water and loss of plant
photosynthetic material devastates root systems and aboveground plant production
is greatly diminished. This loss of
plant cover on the ground leads to higher soil temperatures and increased
evaporation of soil moisture since there is no protective insulation from the
plants.
 |
| Overgrazing in this pasture will lead to more runoff and less plant production. Credit: Mark Tyson, AgriLife Extension |
In 2011, Texas lost 50.5 million acre-feet of water
reserves, which is enough to cover Texas to a depth of 3.5 inches. Most of the decline, 70 to 80 percent,
evaporated from soils, according to a study cited by this Circle
of Blue article.
When raindrops hit bare soil, it is comparable to a bomb that
does significant damage to the soil.
Raindrop impacts can dislodge soil particles, which can lead to greater
erosion or can plug up soil pores that seal the surface thereby reducing
infiltration (See Conservation of
Soil Resources on Lands Used For Grazing).
Either way, there is less rain infiltrating into the ground that can
benefit plants later in the season or replenish groundwater levels.
In the graph below, you can see the management styles of
three different cattle producers. The producer on the far left (Producer A) grazed
his pastures hard leaving only 100 pounds of forage per acre (essentially bare
ground) in January. The producer on the
far right (Producer C) maintained 1500 pounds of forage per acre in his
pastures in January. Producer A
received 16.9 inches of rain and grew around 1800 pounds of forage per acre,
while Producer C grew almost 4000 pounds of forage per acre with only 9.7
inches of rain!
How did Producer C do this? By leaving grass in the pasture,
he was able to capture more rainfall and his plants responded much better since
their root structures were intact and the leaves were able to start
photosynthesizing quickly. (Read Managing Residual
Forage for Rangeland Health)
Another important concept to realize is that organic matter
in the soil is crucial from a nutrient- and water-holding standpoint. Undisturbed prairie soils typically have
about 5% organic matter in the soil, whereas heavily grazed or cropped lands
may have less than 2%. A more complete
discussion on this can be found in an article in the February 2013 edition of The Cattleman.
A study done by Thurow, Blackburn and Taylor (1986) in Texas
compared the infiltration and runoff rates between native grasses and
introduced sodgrasses, such as bermudagrass, to see which was more
effective. Researchers found that
natives allowed 75% of the rainfall to infiltrate so that only 25% ran off,
whereas sodgrasses allowed 54% of the rain to infiltrate, leading to 45%
runoff. The water that was lost on the
sodgrass field represents a loss in production as less water is in the soil and
the potential for erosion is greater.
Also, bermudagrass and other introduced grasses require fertilizers and
other inputs which are becoming more expensive every year, whereas natives
require very little inputs and have an additional benefit of providing wildlife
habitat, which can be an economic opportunity for landowners.
With current
drought conditions expected to persist until 2020, landowners must protect
their greatest asset, soil. Nothing else
will affect your land’s productivity more than if your topsoil washes away,
especially since it takes 100 years to build one inch of topsoil! There are practices you can do to reduce
erosion, and increase infiltration and organic matter (read Improving Rainfall
Effectiveness on Rangeland):
1.
Match the number of grazing animals to the forage
production on your land
2.
Maintain plant cover to protect soil and hold
moisture
3.
Rotate cattle to allow rest for plants
4.
Increase plant diversity with different grasses
and forbs
5.
Minimize soil disturbance by using reduced or
no-till cropping practices
6.
Manage brush cover levels to allow more grass
and forb growth
Take advantage of the rain you get because, as Gary Price of
the 77 Ranch says, “You can’t control how much rain you get, but you can
control how much you keep.”
Learn more about this from the Texas A&M AgriLife
Extension State Forage Specialist in a webinar called, Turning
Your Land Into a Sponge.
Be sure to contact your County Extension Agent, Natural Resources
Conservation Service Center, and Texas
Parks and Wildlife Biologists for help developing grazing and wildlife
management plans that accomplish these goals on your property.
Check out the Natural Resource Conservation Service Soil
Health Initiative
Thurow, T.L., W.H. Blackburn, and C.A. Taylor, Jr. 1986.
Hydrologic characteristics of vegetation types as affected by livestock
grazing systems, Edwards Plateau, Texas.
J. Range Management. 39: 505-508.