Soil Survey of Karnes County, Texas - Soil Data Mart - US ...
Soil Survey of Karnes County, Texas - Soil Data Mart - US ...
Soil Survey of Karnes County, Texas - Soil Data Mart - US ...
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84 <strong>Soil</strong> <strong>Survey</strong><br />
climax plant species, and reduces infestations <strong>of</strong><br />
noxious weed and brush. However, desirable plants<br />
can be severely damaged or killed if the soil surface is<br />
too dry, allowing the fire to reach the plant crowns and<br />
roots. Burning is not recommended more <strong>of</strong>ten than<br />
once every three years to avoid interfering with the<br />
regrowth cycle <strong>of</strong> perennial grasses. Prescribed<br />
burning is an effective management tool that can be<br />
substituted for chemical or mechanical treatment.<br />
Planned Grazing Systems. The objective <strong>of</strong> this<br />
practice is to rotate the grazing <strong>of</strong> livestock through<br />
two or more pastures in a planned sequence for a<br />
specified period <strong>of</strong> time. A planned grazing system<br />
may be relatively simple in design when only two<br />
pastures are used, or may be more complex and<br />
management intensive when one or two herds and<br />
many pastures are used. To be successful, it must be<br />
tailored to conditions existing in each ranch unit and<br />
meet the needs <strong>of</strong> the plants and animals as well as<br />
the rancher.<br />
Table 7 shows for each soil in the survey area that<br />
supports range vegetation, the range site and the<br />
potential annual production in favorable, average, and<br />
unfavorable years. Only soils that are used as<br />
rangeland or are suited to rangeland are listed.<br />
A range site is listed for each soil map unit. The<br />
relationship between soils and vegetation was<br />
established during this survey; thus, range sites<br />
generally can be determined directly from the soil<br />
map. <strong>Soil</strong> properties that affect moisture supply and<br />
plant nutrients have the greatest influence on the<br />
productivity <strong>of</strong> range plants. <strong>Soil</strong> reaction, salt content,<br />
and a seasonal high water table are also important.<br />
Potential annual production is the amount <strong>of</strong><br />
vegetation that can be expected to grow annually on<br />
well managed rangeland that is supporting the<br />
potential natural plant community. It includes all<br />
vegetation, whether or not it is palatable to grazing<br />
animals. It includes the current year’s growth <strong>of</strong> leaves,<br />
twigs, and fruits <strong>of</strong> woody plants. It does not include<br />
the increase in stem diameter <strong>of</strong> trees and shrubs. It is<br />
expressed in pounds per acre <strong>of</strong> air-dry vegetation for<br />
favorable, average, and unfavorable years. In a<br />
favorable year, the amount and distribution <strong>of</strong><br />
precipitation and the temperatures make growing<br />
conditions substantially better than average. In an<br />
unfavorable year, growing conditions are well below<br />
average, generally because <strong>of</strong> low available soil<br />
moisture.<br />
Yields are adjusted to a common percentage <strong>of</strong> airdry<br />
moisture content. The relationship <strong>of</strong> green weight<br />
to air-dry weight varies according to such factors as<br />
exposure, amount <strong>of</strong> shade, recent rains, and<br />
unseasonable dry periods.<br />
Following is a description <strong>of</strong> the 17 range sites in<br />
<strong>Karnes</strong> <strong>County</strong>: Blackland, Chalky Ridge, Clay Loam,<br />
Clayey Bottomland, Gravelly Ridge, Gray Sandy<br />
Loam, Lakebed, Loamy Bottomland, Loamy Sand,<br />
Rolling Blackland, Sandy, Sandy Loam, Shallow,<br />
Shallow Ridge, Shallow Sandy Loam, Sloping Clay<br />
Loam, and Tight Sandy Loam.<br />
Blackland range site. The Elmendorf-Denhawken<br />
complex soils, map unit EdB, are in the Blackland<br />
range site. The climax vegetation is an open grassland<br />
prairie. A few large live oaks, elm, and hackberry trees<br />
are along drainageways and in motts. The composition<br />
by weight is 95 percent grasses, and 5 percent forbs.<br />
This site has high natural fertility. In climax stage,<br />
little bluestem, indiangrass, and fourflower trichloris<br />
produce almost half <strong>of</strong> the forage. Other grasses, such<br />
as Arizona cottontop, sideoats grama, <strong>Texas</strong><br />
wintergrass, <strong>Texas</strong> cupgrass, tall dropseed, pinhole<br />
bluestem, vine-mesquite, and plains bristlegrass,<br />
produce the rest. Many palatable forbs and legumes<br />
are native to the site.<br />
Overgrazing by cattle eventually kills out the<br />
decreaser grasses, such as fourflower trichloris,<br />
indiangrass, sideoats grama, and little bluestem.<br />
These are replaced by increaser plants, such as silver<br />
bluestem, <strong>Texas</strong> wintergrass, tall dropseed, and other<br />
mid grasses. If overgrazing continues, buffalograss,<br />
<strong>Texas</strong> grama, tumblegrass, threeawns, annual weeds<br />
and annual grasses invade the site along with noxious<br />
brush species, such as mesquite, spiny hackberry,<br />
Retama, agarito, lotebush, and huisache.<br />
Chalky ridge range site. The Shiner soil, map unit<br />
SrD, is in the Chalky Ridge range site. This site is a<br />
true prairie site. Large liveoak trees, occuring either<br />
singly or in small motts, <strong>of</strong>fer some shade. The<br />
scattered trees, rolling topography and many native<br />
flowering forbs make this an attractive site. The<br />
composition by weight is 85 percent grasses, 10<br />
percent forbs, and 5 percent woody plants.<br />
The herbaceous plant community is dominated by<br />
little bluestem, which generally makes up a little more<br />
than half <strong>of</strong> the total grass composition. Indiangrass,<br />
big bluestem, Florida paspalum, and Canada and<br />
Virginia wildrye are also important and are <strong>of</strong>ten the<br />
dominant grasses. Sideoats grama, silver bluestem,<br />
and tall dropseed are mid grasses usually present in<br />
smaller amounts. Many forbs and legumes provide<br />
valuable grazing and an attractive landscape.<br />
As retrogression occurs, the tall grass species<br />
decrease and are replaced by sideoats grama, <strong>Texas</strong><br />
wintergrass, silver bluestem, buffalograss, threeawns,<br />
and less palatable forbs. With continued abuse, short<br />
grasses, such as red grama, hairy grama, <strong>Texas</strong><br />
grama, tumblegrass, and threeawns, invade along with