Because of a cow's unique ability to convert forage resources to muscle, beef production and profitability are tied to the amount of precipitation that can be utilized by live plants.

Author Charles Dudley Warner once wrote, "Everybody talks about the weather, but nobody does anything about it."

While it's true we can't control the wind or predictably manipulate rainfall, there are management tools available that will enable you to take advantage of the precipitation your land receives to maximize production. More rainfall doesn't mean more production if that water doesn't stick around long enough to be used.

The hydrologic cycle

The amount of water on earth never changes. But its form and location is constantly in a changing cycle. Precipitation that reaches the ground either evaporates, infiltrates into the soil or runs off the soil surface to ponds, lakes or oceans. That small amount of precipitation that infiltrates into the soil is the key to plant life and productivity. Synonymously, plant life and soil surface characteristics affect the amount of water that infiltrates and is retained in the soil.

"Most ranching occurs in arid or semi-arid regions so generally you don't have enough water to begin with. But when it does rain you want that water to go into the soil and not run off," says Butch Taylor, superintendent of the Texas A&M research station in Sonora, Texas.

The conceptual model of water use on rangeland (see chart) illustrates how forages beneficial to beef production are able to utilize only a small percentage of the precipitation that falls on south Texas rangelands. Where each drop of water falling on your pasture goes depends on the climate, geology and the vegetation on your land.

Improving rainfall effectiveness

Whether you produce beef on arid range, lush grass pastures or the short grass prairie, management of your forage and soil resources can improve the effectiveness of rainfall by: * Reducing runoff * Avoiding over-grazing * Controlling undesirable weeds and brush * Minimizing evaporation

Reduce runoff

The process of harnessing the sun's energy in green plants and converting that energy to protein through cattle would never be possible without sustainable soil resources. Surface runoff represents a serious loss of water and the erosive nature of runoff transports soil and nutrients from the land. The loss of soil reduces the quantity of water that can be stored at any one time. This not only limits forage production but results in plants running out of water faster, increasing the frequency and severity of drought.

"The first step in capturing rainfall is ensuring that you have as much of the ground covered as possible. That means covered by green growing plant material or by dead plant litter," says Jim Gerrish, forage specialist at the University of Missouri's Forage Systems Research Center in Linneus, Mo. " If pastures are always being grazed down to 11/2 to 2 inches you are going to have bare ground. If you have bare soil between plants, you can count on having run off. But if you have plant residue on the soil surface it will act as a sponge and hold the water in place."

Vegetative cover also protects the soil's surface from raindrop splash. This is important because water infiltrates into the ground through pore structures in the soil's surface. When raindrops hit bare ground they break down soil structure, closing the pores to infiltration.

Surface water sources, including ponds, lakes and rivers, depend on the runoff of rainfall to maintain water volume. However, any negative impact of water infiltration on surface-water volume is minimal. Improved plant cover can potentially increase infiltration and total run off at the same time.

"You can get more runoff even with more grass because grasses use less water than brush," explains Bob Knight, associate professor of Rangeland Ecology and Management at Texas A&M University. "Grass plants use some water in the summertime. Then when the winter rains come the amount of water in the soil builds up and it takes less to recharge the soil to peak water holding capacity. The result is more surface runoff when additional rains come in the spring."

Avoid over-grazing

During the summer, the evapotranspiration rate of forages growing on pasture around the Missouri Forage Systems Research Center will run 1/4 inch to 3/10 of an inch per day.

"How often do we get 13/4 inches of rain every week? Not very often," says Mr. Gerrish. "Capturing as much spring rain as possible to store in the soil profile is what really keeps your pastures growing in the summer time."

How you manage your pastures has a significant impact on water holding capacity. In fact, poor management this winter can negatively affect infiltration by spring. Feeding hay to your cowherd on the same pasture all winter allows cattle to graze every plant down short. In addition, the hoof action during the wet part of winter and spring compacts the soil.
"Avoiding keeping cattle on the same pasture throughout the entire winter is going to make that pasture more resilient when spring comes and better able to take in water and store it," says Mr. Gerrish.

Though environments differ, the factors that allow soil to hold more water are similar. A key ingredient in increasing water-holding capacity is adequate forage residual. Repeatedly over- grazing pastures hurts soil structure, slows infiltration and reduces the amount of organic matter on the soil surface.

Grazing plants too short is a result of over stocking a pasture. And the more animal pressure you put on a pasture the more the soil gets compacted. This problem is magnified when overgrazing decreases root mass that would otherwise help break up the soil. Leaving that taller residual is going to help your root system.

"Here in the Midwest we usually get the freezing and thawing that breaks the soil compaction back down. At a low to moderate stocking rate, each winter will correct the compaction that you created the previous summer," says Mr. Gerrish. "But with sustained high stocking rates, we don't see it going back to as low a level each year."

Control undesirable weeds and brush

While having any plant cover is better than bare ground, not all plants in a pasture contribute to livestock production. Weed and brush plants take water from the grass that could potentially be used for livestock production. It's estimated that mesquite use as much as 100 gallons of water for each pound of above ground plant material produced. Perennial grasses use less water, between 40 and 75 gallons, for each pound of usable plant material.

In research trials done in south Texas on mixed brush, researchers found that forage production can increase significantly upon implementing brush control measures.

"Research I have done with juniper has shown that the surface area below and around a mature tree may only be able to produce 200 to 300 pounds of forage per acre per year," says Darrell Ueckert, a Texas A&M professor of rangeland ecology and management. "But if you kill that tree and leave it standing, within two years that same land under that tree can be producing 2,000 pounds of forage per acre. That's how severe juniper competes with forage plants for water."

Clearing brush not only frees up water supplies needed by more efficient grasses and forage plants, it can increase the amount of water that percolates below the root zone replenishing deep aquifers. Dr. Knight explains that herbaceous forages only extract moisture out of the surface because their roots reach down only 3 to 5 feet. Brush roots will go down 15 or 20 feet.

Minimize evaporation

"Cedar and other woody plant species also catch a significant amount of rainfall in their canopy that would potentially go into the soil to grow grass or even recharge the underground aquifer," says Terry Bidwell, rangeland management specialist at Oklahoma State University. "When rain water is caught in the canopy much of it will evaporate and never even reach the ground. And the more arid the climate is the more significant that interception of water is."

Interception loss refers to the amount of water that adheres to above-ground vegetation and directly evaporates back to the atmosphere. Because of the differences in structure, area and texture of plant surfaces, vegetation greatly influences interception. Forage resources can be manipulated to reduce evaporation and canopy interception while at the same time protecting soil surfaces from the effects of heat and wind.
"Juniper has a very dense canopy year round, which can intercept a lot of rainfall," says Dr. Taylor.

In Sonora, Texas, precipitation averages 22 inches per year according to Dr. Taylor. If rangeland has Juniper canopy covering over 30 percent of the surface, he estimates only about 16 inches of that rainfall will actually reach mineral soil because of interception. Allow the canopy to cover 60 percent, a common occurrence, and only about 9 inches of rainfall would ever reach the ground.