OAKTrust Digital Repository (Texas A&M Univ)

This is a list of all items owned by the Texas A&M University at Qatar Library upon its closing in 2024. Preserved for historical significance

Torres, Shaun

TAMUQ Library Collection November 12, 2024

Lesikar, Bruce J.

Sampling for Bacteria in Wells
E-126
11/01
Water samples for bacteria tests must always be col-
lected in a sterile container. The procedure for collect-
ing a water sample is as follows:
1. Obtain a sterile container from a Health
Department Laboratory or contact your local
Extension Service office.
2. Select the cold water faucet at which you will col-
lect the sample. This faucet should have the aera-
tor removed. Do not collect a sample from: a hot
water faucet; a hot and cold water mixing faucet; a
leaky faucet; any faucet that delivers softened, fil-
tered or otherwise treated water; or from a hose
attached to a faucet.
3. Sterilize the inside surface of the faucet by flam-
ing with a propane torch (a disposable butane
lighter is fine) or a homemade torch can be made
by dipping a cotton ball in rubbing alcohol and
holding the cotton ball with a long pliers, light the
cotton ball. Do not wipe the end of the faucet after
flaming with the torch. 
4. Wash hands thoroughly before collecting the
sample. 
5. Run the water at full flow for five minutes to clear
the water lines and bring in fresh water. 
6. Reduce the flow to a pencil stream to prepare for
sampling. 
7. Carefully open the sterile bottle. Hold the cap in
one hand and the bottle in the other (do not set the
cap down or touch the inside of the bottle or cap).
Fill the bottle to the top without overflowing.
Also, remember to not let the water flow over
your hand as the water enters the bottle. 
8. Close the bottle immediately after collecting water
sample.
Refrigerate the sample and transport it to the laborato-
ry (in an ice chest) as soon after collection as possible
(six hours is best, but up to 30 hours). Many labs will
not accept bacteria samples on Friday so check the
lab’s schedule. Mailing bacteria samples is not recom-
mended because laboratory analysis results are not as
reliable. The laboratory analysis generally has a fee of
$8 to $25.
Iron bacteria is another contaminant which forms a
very obvious slime on the inside of pipes and fixtures.
A water test is not needed for identification. Check for
a reddish-brown slime inside a toilet tank or where
water stands for several days.
*compiled by Bruce J. Lesikar, Extension Agricultural Engineer,
9/92


Sampling for Bacteria in Wells

McFarland, Mark  L.

Dozier, Monty C.

Runyan, R. Craig

Shock chlorination is a method of disinfect-ing a water well. It is recommended whena water system is contaminated with bacte-
ria.  Contamination can occur when the well is
installed, when repairs are made to the pump or
plumbing, or when rainfall runoff enters the well.
If the groundwater itself is the source of bacteria,
the system will be contaminated again every time
water is pumped into the plumbing. In that case,
continuous chlorination (or the use of another con-
tinuous disinfection method) will be necessary to
ensure the safety of the water supply.
Shock chlorination introduces very high levels of
chlorine into a water system. During the disinfec-
tion process, water from the system is not suitable
for consumption and neither people nor animals
should have prolonged contact with it. Make the
treatment when faucets and toilets will not be in
use for at least 12 hours, preferably 24 hours. If
there is an automatic watering system for animals
and irrigation, provide an alternate water source
during the treatment period. 
Most water treatment equipment (such as water
heaters, softeners and pressure tanks) should also
be disinfected. Drinking water filters, such as car-
bon filters, should be temporarily disconnected or
by-passed during shock chlorination. Activated car-
bon filters left in place during the chlorination
process will actually remove the chlorine until they
become overloaded. Before treating equipment,
read owner’s manuals or manufacturers’ literature
to avoid damaging components.
Chlorine Sources
Chlorine is highly toxic to bacteria at concentra-
tions of 200 milligrams per liter and above. Shock
chlorination of a well involves adding a chlorine
solution to the water supply until it reaches a con-
centration of 200 milligrams per liter, and then cir-
culating it to disinfect all parts of the water system.
Chlorine is available in several different forms.  The
two most often used for well disinfection are dry
chlorine and liquid household bleach.  Dry chlorine
contains about 65 percent calcium hypochlorite;
bleach contains about 5.25 percent sodium hypo-
chlorite. When used properly, they are equally
effective for disinfecting wells. Do not use bleach
with a “fresh scent,” lemon fragrance or other addi-
tives because it may contain chemicals not suitable
for human or animal consumption. 
Chlorination Procedure
The amount of chlorine needed is determined by
the amount of water standing in the well. Contact
the company that constructed your well to find out
the water well depth and static water level. The
standing water depth in the well will be the well
depth minus the static water level.  For example, a
water well 110 feet deep with a static water level of
90 feet would contain a standing water depth of 20
feet (110 feet - 90 feet = 20 feet).  Table 1 lists the
amount of ordinary household bleach (5.25 percent
hypochlorite) needed for shock chlorination based
on the casing diameter of the well and the standing
Shock Chlorination 
of Wells
Mark L. McFarland, Associate Professor and Extension Soil Fertility Specialist
Monty C. Dozier, Assistant Professor and Extension Specialist — Water Resources
The Texas A&M University System
R. Craig Runyan, Program Coordinator, Extension Plant Sciences Department,  
New Mexico State University  
L-5441
6-03
2. Remove the plug or screen on the well cap so
you have access to the inside well casing.
Dilute the liquid bleach by placing the appro-
priate amount of bleach (see Table 1) in a 5-
gallon bucket and filling the bucket with clean
water. If you are using dry chlorine, place the
proper amount (based on Table 2) in a 5-gallon
bucket and fill the bucket with clean water to
dissolve the bleach. Place a funnel in the
well’s access hole and pour the solution
around the sides of the well casing.
3. Connect a garden hose to a nearby faucet and
run the hose to the funnel in the well’s access
hole to wash down the inside of the well.
Continue the washing process for 10 minutes
and make sure a strong chlorine smell can be
detected. Start and stop the well pump several
times to mix the chlorine thoroughly with the
well water.  
4. Do not operate the water system for 2 hours.
5. After 2 hours, open the faucet closest to your
well, allow water to run until a strong odor of
chlorine is detected, then close the faucet.
Proceed to the next faucet and repeat.
water depth in the well. If the standing water depth
of the water in the well is unknown, use a volume
of bleach equal to two times the depth value for the
appropriate casing diameter. For example, an 8-inch
casing diameter with unknown standing water
depth would require 3 gallons of household bleach.
Do not use more bleach than recommended
because it is not necessary and will require addi-
tional flushing before you can use the water. Table
2 shows the amount of dry chlorine (high-test
hypochlorite) to use. High-test hypochlorite is avail-
able in powder or tablet form.
To treat a well:
1. First, drain as much water from the system as
possible. If the system has a pressure tank that
contains a bladder, the rubber air-water sepa-
rator in the tank may be damaged by the chlo-
rine solution. Check your manufacturer’s
guide to see if the pressure tank should be
bypassed. If the pressure tank has no bladder,
release the air to allow the tank to be filled
with chlorinated water. Also drain all hot
water heaters to allow chlorinated water to
circulate through the hot water system. 
2
Table 1.  Amount of chlorine bleach needed for shock chlorination.
Laundry bleach (about 5.25% hypochlorite)
Standing water depth Casing diameter
in well (in feet) 4 inches 6 inches 8 inches 10 inches 12 inches
10 1/ 2 cup 1 cup 11/ 2 cups 1 pint 2 pints
25 1 cup 1 pint 2 pints 3 pints 41/ 2 pints
50 1 pint 1 quart 2 quarts 3 quarts 1 gallon
100 1 quart 2 quarts 1 gallon 11/ 2 gallons 2 gallons
150 3 pints 3 quarts 11/ 2 gallons 2 gallons 3 gallons
Table 2.  Amount of dry chlorine needed for shock chlorination.
High-test hypochlorite (HTH 65-75% hypochlorite)
Standing water depth Casing diameter
in well (in feet) 4 inches 6 inches 8 inches 10 inches 12 inches
10 — — — — —
25 — — — 1/4 lb. 1/4 lb.
50 — — 1/3 lb. 1/ 2 lb. 3/4 lb.
100 — 1/3 lb. 3/4 lb. 1 lb. 11/ 2 lbs.
150 1/4 lb. 1/ 2 lb. 1 lb. 11/ 2 lb. 4 lbs.
Continue until chlorine is detected in all
faucets.   If the odor is not detected, check the
rate of chlorine from Table 1 or Table 2 and
add more chlorine to the well, repeating steps
one through four.
6. Do not operate the water system for at least
12 hours, preferably 24 hours.
7. Next, flush the system of remaining chlorine.
Begin by turning on outside faucets and letting
the water run until the chlorine smell dissi-
pates.  Let the water run on the ground to
reduce the load on your septic system.  High
loads of chlorine in the septic tank can kill
beneficial bacteria and make it necessary to
re-inoculate the septic system. But do not let
the chlorinated water run onto lawns, gardens
or other plants because chlorine can injure
them. Place the garden hose so that it drains
into a field or low-lying area away from desir-
able plants.  Be careful not to discharge the
chlorinated water directly into ponds, lakes,
rivers or streams.
Precautions
Wear protective eyewear and clothing (rubber boots and gloves)
when mixing and using household bleach or dry chlorine. Be
careful not to breathe the fumes from dry chlorine tablets. If you
have tablets left over, store them in an airtight container,
because moisture in the air will “melt” the tablets.
Always have a 5-gallon container of clean, fresh, unchlorinated
water nearby for emergencies. If you accidently get chlorine in
your eyes or on your skin, flush immediately with fresh water
for 10 to 15 minutes.  Then seek medical attention right away.
8. Finally, turn on the indoor faucets until the
system is completely flushed.
9. After chlorination, have the well water tested
again for bacterial contamination.
10. If bacteria are still detected in the well water,
repeat the chlorination process and then test
the water again.
11. If bacterial contamination is detected a third
time, check for potential sources of reinfection
such as 
• an improperly designed wellhead, or  
• livestock pens or septic tanks near the well-
head. 
It might be necessary to install a continuous chlori-
nation system or other continuous disinfection sys-
tem.
For more information about wellhead protection,
see the Tex-A-Syst rural water well assessment pub-
lications (B-6023 through B-6032) available from
Texas Cooperative Extension.
3
Produced by Agricultural Communications, The Texas A&M University System
Extension publications can be found on the Web at: http://tcebookstore.org
Visit Texas Cooperative Extension at: http://texasextension.tamu.edu
Educational programs of Texas Cooperative Extension are open to all people without regard to race, color, sex, disability, reli-
gion, age or national  origin.
Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8,
1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Chester P. Fehlis,
Director, Texas Cooperative Extension, The Texas A&M University System.
5M, New
This publication was funded by the Rio Grande Basin Initiative administered by the Texas Water Resources Institute of
Texas Cooperative Extension, with funds provided through a grant from the Cooperative State Research, Education, and
Extension Service, U.S. Department of Agriculture, under Agreement No. 2001-45049-01149.
Information in this publication came from University of Nebraska
publication G95-1255A, Auburn University publication ANR-790,
Texas Natural Resource Conservation Commission publication
GI-005, and other sources.
For additional information visit: http://soilcrop.tamu.edu or
http://water.tamu.edu


Shock Chlorination of Wells

Provin, Tony L.

Featley, Same E.

 
1 
SCS-2009-08 
Mark L. McFarland, Professor and Extension State Water Quality Specialist 
Sam E. Feagley, Professor and Extension State Environmental  Specialist 
Tony L. Provin, Associate Professor and Extension Laboratory Director 
Texas AgriLife Extension Service 
     Petroleum and natural gas are major sources of revenue in Texas.  However, disturbance 
caused by construction of drilling locations, oilfield roads, and installation of pipelines can re-
sult in reduced crop production, increased susceptibility of the damaged sites to erosion, and in-
creases in noxious and poisonous plant densities.  In addition, on-site disposal of drilling fluids 
used in the drilling process can create problems if not managed properly.  Drilling fluids have 
been and currently are land applied in many parts of Texas.  In some areas, the use of clayey 
drilling fluids on sandy soils has improved water holding capacity and plant growth.  However, 
in many areas of the state, improper rates of application of high salt drilling fluids have resulted 
in the death of plants and severely damaged soils that have failed to recover even after many 
decades (Photo 1).   
BACKGROUND 
Photo 1.  Denuded oil well reserve pit in west Texas with high soil salt concentrations. 
Land Application of Drilling Fluids: 
Landowner Considerations 
 
2 
Photo 2.  Oil well reserve pit containing drilling fluids.  
The Environmental Protection Agency (EPA) 
classifies oil and gas drilling fluids as 
“special wastes” which are exempted from 
amendments to the Resource Conservation 
and Recovery Act (RCRA) issued by Con-
gress in 1980.  As a result, regulations re-
garding the handling and disposal of oil-field 
generated wastes vary from state to state.  
The Railroad Commission of Texas (RRC) is 
authorized to regulate disposal of drilling flu-
ids under Title 16 (Economic Regulation), 
Part 1 (Railroad Commission of Texas), 
Chapter 3 (Oil and Gas Division) of the 
Texas Administrative Code.  Under State-
wide Rule 8, adopted by the Railroad Com-
mission, authorized disposal procedures in-
clude landfarming and burial of certain drill-
ing wastes, including drilling fluids. 
 
Drilling fluids, also called drilling muds, 
typically consist of about a 5% slurry of ben-
tonite clay in a base fluid of water, diesel, or 
mineral oil, an organic material such as lig-
nite or lignosulfonate to stabilize the slurry, 
and a density increasing material, usually 
barite (BaSO4), to help float out rock parti-
cles.  However, the quantity and chemical 
composition of a particular drilling fluid will 
vary with conditions in the hole, such as 
depth and type of formation.  These fluids 
remove cuttings from the hole, cool the drill 
bit, and seal off porous geologic strata.  The 
fluid is periodically pumped into a reserve pit 
(constructed earthen pit) circulated to allow 
cuttings to settle, and then reused (Photo 2).  
When drilling is completed, much or all of 
the fluid is disposed of in the pit, allowed to 
dry, and then mixed with soil from the pit 
berms or simply covered.  In other situations, 
drilling fluids may be disposed of by removal 
and transport to an approved landfill, or by 
land application.  
Landfarming or land application is a process whereby drilling fluids are spread on the land surface.  
The rate of application depends on the characteristics of the soil and the chemical composition of the 
drilling fluid.  Land application is often preferred to reduce the costs of disposal, and may be con-
ducted either on-site (where the drilling occurred) or at an off-site location.  This process also is used 
to treat and/or dilute potentially harmful constituents in the drilling fluid, when present.  These con-
stituents may include petroleum hydrocarbons, salts and/or heavy metals. 
 
3 
Petroleum hydrocarbons including oil and grease can be toxic to plants in modest concentrations 
either due to direct contact or through adverse effects on soil properties.  When oil is spilled on 
growing plants, low molecular weight compounds, for example fuel oil, act as a solvent on the 
lipid membranes of tender plant parts.  Total soil hydrocarbon concentrations greater than 1% have 
been found to be toxic to most plant species and this level is normally considered the threshold 
between non-contamination and contamination.  Soil oxygen levels are reduced because diffusion 
of oxygen through the oil and/or grease layer is poor and because microbes use the available oxy-
gen as they breakdown the oil.  As a result, the soil can become anaerobic (low oxygen), which is 
limiting to plant growth.  In addition, plant available nutrients (particularly nitrogen and phospho-
rus) are rapidly used by these microbes in the process of degrading the oil and can become defi-
cient for plant growth.  Finally, and commonly the most damaging to plant growth, soil particles 
coated with oil can become hydrophobic which reduces water infiltration, drainage and storage in 
the soil, and its availability to plants. 
 
Salts in drilling fluids can affect both plants and the soil.  The salts present in drilling fluids can 
come from 1) the materials used to formulate the drilling fluids, and/or 2) poor quality groundwa-
ter or salt containing geologic formations that are contacted during drilling.  High levels of soluble 
salts decrease water availability to plants, basically creating a drought-like stress which can cause 
plants to wilt and potentially die.  A soil is typically considered salt-affected or “saline” when the 
electrical conductivity of the saturated paste extract exceeds 4 millimhos per centimeter (mmhos/
cm).  However, sensitive plants may be affected by even lower soil salt levels. In loamy to clayey 
soils and under drying conditions, salts will often wick to the soil surface and accumulate, some-
times producing a white appearance (Photo 3). Several of the salt elements like sodium and chlo-
ride can be toxic to plants in high concentrations.   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                                 
 
 
 
 
 
 
 
Another element, boron, can be toxic to some plants even at relatively low concentrations (< l part 
per million, ppm) in the soil.  Sodium also can have an adverse effect on the soil by degrading soil 
structure.  Soils affected by sodium often will be powdery and structureless on the surface when 
dry, or can become hard and very compacted.  This reduces air and water movement into the soil 
and will limit plant growth.  A sodium adsorption ratio (SAR) of 10 or more indicates the potential 
for adverse effects of sodium on soil physical properties.   
Photo 3.  Salt accumulation on the surface of the soil at a reserve pit. 
 
4 
Photo 4.  Revegetated reserve pit. 
Heavy metals are elements that may or may not be plant nutrients, but can be harmful to plant and/
or animal health in low to high concentrations depending on the element.  Some heavy metals will 
cause plant death at high concentrations.  Others can accumulate in plant tissue (without harm to 
the plant) to levels which are harmful or toxic to animals and/or humans. The heavy metals most 
commonly found in drilling fluids include arsenic, barium, chromium, copper, lead, nickel and 
zinc.  The amounts present will depend on the formulation of the drilling fluid and the geologic 
formations encountered during the drilling process. 
 
LAND APPLICATION 
  
The decision to land apply drilling fluids should be based on the chemical composition of the drill-
ing fluid, and the amount and characteristics of the land area available.  The first step is to obtain a 
chemical analysis of the drilling fluid and a representative (composite) sample of the native soil 
from the proposed land application area.  No single measurement, such as a simple chloride analy-
sis, is sufficient to properly evaluate and manage drilling fluid disposal.   A thorough analysis 
should include the following measurements for both the drilling fluid and native soil unless other-
wise specified: 
 
1. Total salts – measured as the electrical conductivity (EC) of the saturated paste extract 
and reported in parts per million (ppm) or millimhos per cm (mmhos/cm). 
2. Extractable individual ions – calcium, magnesium, sodium, boron, chloride, and sulfate
-sulfur measured in the saturated paste extract and reported in milligrams per kilogram 
(mg/kg) or ppm. 
3. Sodium Adsorption Ratio (SAR) – calculated from the saturated paste analyses for cal-
cium, magnesium, and sodium. 
4. Total heavy metals – arsenic, barium, chromium, copper, lead, nickel, and zinc reported 
in mg/kg. 
5. Total petroleum hydrocarbons (TPH) – drilling fluid only, reported in mg/kg. 
6. Routine + micronutrient soil nutrient test – pH, and extractable nitrate-nitrogen, phos-
phorus, potassium, calcium, magnesium, sodium, sulfur, copper, iron, manganese, and 
zinc. 
7. Soil texture – native soil only.  
8. Cation exchange capacity – native soil only. 
 
5 
A qualified professional can utilize the re-
sults of these tests to determine if land appli-
cation is appropriate for a particular situation.  
If so, they can provide the proper rate of ap-
plication (barrels per acre, tons per acre, or 
inches of depth) of drilling fluid so that the 
process does not cause long-term adverse ef-
fects on soil properties.  These results also 
can be used to determine if additional soil 
amendments may be needed to promote treat-
ment of the waste.  For example, gypsum 
(calcium sulfate) may be recommended to 
offset high levels of sodium in the drilling 
fluid and prevent problems with soil struc-
ture.  In other cases, nutrients are applied to 
support the growth of soil microbes capable 
of decomposing hydrocarbons, and to en-
hance plant growth for site recovery. 
 
Land application should be conducted care-
fully to ensure that the rate of application is 
correct.  Excessive rates can seriously dam-
age the soil, and create long-term problems 
which are very difficult and expensive to cor-
rect.  Once the drilling fluid has been applied 
it is typically disked or otherwise thoroughly 
mixed and incorporated into the upper 4 to 6 
inches of soil.  This assists with the decom-
position of any organic materials and initially 
dilutes salts and other elements that may be 
present in high concentrations.  The area may 
then be prepared and planted with a desirable 
plant species or species mixture (Photo 4). 
 
Land owners are advised to develop a formal 
contractual agreement with the company or 
individual responsible for disposal of the 
drilling fluid.  The agreement should stipulate 
testing requirements for drilling fluids and 
native soils, the land application procedures 
and limits, and any expectations for replant-
ing and/or recovery of the impacted land.            
This may include periodic monitoring and 
further soil testing on the site.  In some cases, 
it is desirable to require annual or semi-
annual testing to ensure that constituent lev-
els are within acceptable concentrations.  In 
addition, specific requirements for vegetation 
recovery may be established, such as percent 
ground cover and/or survival for a specified 
period of time into the future (e.g. 1 to 3 
years).  The landowner should consider re-
quiring the land application company to post 
a bond to insure longer-term compliance with 
specific land management requirements.  The 
costs of sample collections, analyses, soil 
amendments such as gypsum and fertilizer, 
and selected seeds or vegetation, etc. can be 
included in the contractual agreement as the 
responsibility of the company or individual 
responsible for the disposal of the drilling 
fluids. 
 
Careful development of a management plan 
for land application of drilling fluids is im-
portant to ensure that the land resource is 
utilized in an environmentally sound fashion 
and is protected for the future.  By accom-
plishing this, the surrounding land and water 
resources also will be protected from poten-
tial off-site impacts.  For questions and assis-
tance related to drilling fluid disposal or a 
land application program, contact your local 
district office of the Railroad Commission of 
Texas (http://www.rrc.state.tx.us/).  Web re-
sources include a map of RRC district loca-
tions (http://www.rrc.state.tx.us/forms/maps/
ogdivisionmap.php) and contact information 
for district offices (http://www.rrc.state.tx.us/
contact/index.php).  For more information on 
testing contact the Texas AgriLife Extension 
Service Soil, Water and Forage Testing 
Laboratory (979-845-4816), or your local 
county Extension office. 
Produced by the Department of Soil and Crop Sciences 
For further information go to www.soilcrop.tamu.edu.  
Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, 
age, or national origin. 
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding 
that no discrimination is intended and no endorsement by the Texas AgriLife Extension Service is implied. 


Land Application of Drilling Fluids: Landowner Considerations

Miller, Travis D.

❚❚❚❚❚❚❚
❚❚❚
❚❚
❚❚
❚❚
❚❚
❚❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚ ❚
❚ ❚
❚ ❚
❚ ❚
❚ ❚
❚ ❚ ❚
❚ ❚ ❚ ❚
❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚
❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚
★
★ ★
Texas Agricultural Extension Service
The Texas A&M University System
Phosphorus Fertility in Wheat
It is Not a Question of  How Much But Also Where
Travis D. Miller
Professor and Extension Agronomist
Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socioeconomic level, race,
color, sex, religion, handicap, or national origin.
Texas Agricultural Extension Service • Edward A. Hiler, Interim Director  • The Texas A&M University System • College Station, TX
Winter wheat, like most cool season grass responds
well to phosphorus (P) fertility.  The degree of re-
sponse to added fertilizer depends on several vari-
ables, including the amount of P in the soil prior to
fertilizer application, where relative to the wheat
seed this applied P is located, soil temperature at
planting and for 4 to 6 weeks thereafter, soil pH,
and available moisture in the fertilizer P enriched
zone  during crop growth.  A first logical step in
assessing P needs in wheat is a soil test.  This soil
test will give relative amounts of P in the soil.  If
you can run a stratified soil test, take samples from
the surface (0 to 2 inches), and from 2 to 8 inches.
In western regions of the state where fall rainfall is
limiting to wheat growth, P concentration at the
second (2 to 8") increment is most useful in deter-
mining the need for and amounts of P to be ap-
plied.  In high rainfall areas, where adequate or
excess moisture at the surface is more the rule than
the exception, more attention should be paid to
surface P concentrations with the soil test.
Grazing or winter forage production from wheat is
very important to most Texas wheat growers, with
anywhere from one third to one half of the crop
utilized only as a forage and never harvested for
grain and more than 70% of the total crop grazed
at some time during the growing season.  Due to
this requirement, early and rapid vegetative growth
is very important to Texas wheat growers.  As P
plays a key role in this early forage growth as well
as root and tiller development, it is vital to test soils
and apply appropriate amounts of P prior to or dur-
ing preplant land preparation.  Numerous trials
hroughout Texas have demonstrated that P is as
significant as nitrogen (N) in early forage develop-
ment, that N uptake and utilization are greatly di-
minished in a P deficient crop, and that prevailing
rainfall dictates the most efficient way to incorpo-
rate P.  Deep, banded P application (4 to 8 inch
depth) has resulted in greatly enhanced forage pro-
duction in trials in the Rolling Plains and under
irrigation in the Northern High Plains.  Response
with respect to forage production is greatest with
dry fall weather patterns, which tend to be the rule
rather than the exception over much of west Texas.
Traditional surface incorporation techniques work
best in this same region if unusually wet fall weather
occurs.  Grain yields are similar if adequate rain-
fall is received by mid-February.  In dry spring
weather, wheat treated with deep banded P pro-
duces significantly greater grain yields than wheat
treated with surface incorporated P.  Limited trials
have compared depth of incorporation on deep
banded P.  In very dry weather patterns, P incorpo-
rated to the 7 to 8 inch depth resulted in signifi-
cantly higher grain and forage yields than wheat
with P banded at the 4-inch depth, which  had
greater yields than wheat treated with surface in-
corporated P.  In two years of the study, wheat
treated with P banded at both the 4 and 8 inch depths
was slightly superior to wheat fertilized at only the
8 inch depth.
In higher rainfall climates, where the soil surface
stays moist during most of the fall growing period,
wheat treated with P in the seed furrow at planting
responds better than other P incorporation tech-
niques.  This P placement advantage is more dra-
matic with late planting in cool soils.  Another pro-
duction system in which excellent responses are
obtained to seed furrow P is acid soils.  Acid soils
tend to have high concentrations of available alu-
minum, which causes stunting, unthrifty growth
and low yields of forage and grain.  Seed furrow P
neutralizes some aluminum toxicity.  Seed furrow
P applications have been utilized by some farmers
as a band-aid approach where it is impractical or
economically unfeasible to apply ag lime.  In gen-
eral, even in the drier climates where we see dra-
matic forage and grain yield responses to deep
banded P, seed furrow banding is superior to sur-
face incorporation, as banding concentrates P near
the wheat crown, giving excellent proximity for
early root development and reducing reaction with
cations which make the P fertilizer unavailable. In
oils and climates where fall moisture is abundant
to excess, and a relatively early  planting date in-
sures relatively rapid root development, surface
incorporated P is equivalent to or better than other
application technologies discussed here.
Wheat is not a crop known for its high margin of
return. Drought, spring freeze, winterkill and vari-
ous plant diseases greatly reduce predictability of
grain yields.  Many Texas wheat producers have
opted to use wheat as a dual purpose, forage and
grain crop to reduce risk and have two sources of
income.  It is clear that P fertility is also a risk
management tool, making wheat grain and forage
yields less subject to the vagaries of the weather.
In order to capture the potential of P fertility in our
wheat crop, however, we must assess weather risks
and use our knowledge to place P in the soil pro-
file so that we have the greatest probability for up-
take during the early portion of our growing sea-
son.  Without careful attention to P fertility and P
placement, we know that nitrogen use efficiency is
greatly diminished and cost per unit of wheat for-
age and grain produced greatly increases.
See our website at:  http://soil-testing@tamu.edu


Phosphorus Fertility in Wheat: It is not a question of how much, but also where

McFarland, Mark L.

Feagley, Sam E.

Managing Crop Nutrients Through Soil, Manure and Effluent Testing

Taylor, Gene R., II

White, Richard H.

Abernathy, Scott

Smith, David

Athletic Fields and Water Conservation

Stichler, Charles

Fipps, Guy

Irrigating Sorghum 
i n  S o u t h  a n d  S o u t h  C e n t r a l  T e x a s
Charles Stichler and Guy Fipps*
Because yield is determined by both the number
and weight of seeds, it is vital for growers to under-
stand the plant processes that affect seed develop-
ment. One such process is photosynthesis, in which
green plant tissues take carbon dioxide from the air,
water and nutrients from the soil and energy from
sunlight and convert them into sugars or carbohy-
drates. The products of photosynthesis are also
called photosynthates.
The more active, functioning leaves a plant has,
the more photosynthates it will produce, and thus
the greater its yield potential. To increase yield
potential, growers need to take management steps
that support leaf development, maximize photosyn-
thesis and limit water loss.
A critical component of the photosynthesis
process is water. Water can be said to be part of a
plant’s circulatory system — water moves through-
out the plant, carrying with it plant minerals, nutri-
ents and plant chemicals such as enzymes, proteins,
sugars and carbohydrates. Water evaporates from
the leaf and is replaced with water from the soil in
a process called transpiration. 
A sorghum plant gets more than 75 percent of its
water and nutrients from the top 3 feet of soil.
Plants can use about 50 percent of the total avail-
able water without undergoing stress.
The availability of water is the key factor to con-
sider when deciding on row spacing and plant pop-
ulation. Moisture dictates yield goals, which in turn
dictate seeding rates and spacing. For irrigated pro-
duction, growers should aim for between 70,000
and 80,000 established plants per acre; for dryland
production, the total should be 50,000 to 60,000
W
ATER IS ALL we sell in
agriculture.” Whether
the enterprise is corn,
cattle, cauliflower, cot-
ton, or grain sorghum
water is essential for
its production and the
R
agriculture.” Whether the enterprise is corn, cattle,
cauliflower, cotton, or grain sorghum, water is
essential for its production and the single most
important aspect of production that determines
yield. aspect of production that determines yield.  
Grain sorghum is a tropically adapted plant that
can survive under drought and adverse conditions.
Because of its ability to survive in unfavorable con-
ditions, sorghum is often relegated to poor soils and
poor management.
However, to be profitable, a sorghum crop needs
sufficient water at critical points in its develop-
ment. Therefore it is vital that growers manage irri-
gation properly. If grain sorghum is managed well,
it will produce profitable, high yields. 
Growth and development
Like other grains, the ultimate purpose of a
sorghum plant is to produce seeds. Seed production
is a singular event — the plant’s root, leaf and stem
development are all directed toward this outcome.
*Associate Professor and Extension Agronomist, and
Professor and Extension Irrigation Engineer, The Texas
A&M University System
‘ ATER IS ALL we sell in 
L-5434
2-03
established plants per acre. (For more information,
refer to B-6048, Irrigated and Dryland Sorghum
Production.) 
Yields will be reduced if the plants are too
crowded. The more plants that are established, the
more water the crop will use. If too many are plant-
ed, much of the soil moisture will be used before
the reproductive stage begins, rendering the plants
unable to produce seeds.
Research has been conducted at Texas Tech
University on the amount of water per acre requir-
ed by sorghum. The studies have shown that sor-
ghum at pre-bloom uses 8 to 10 inches of water per
acre and that each additional inch will produce 385
to 400 pounds of grain.
For a grain yield of 7,000 pounds per acre, total
water use — from both soil and plant evaporation —
is about 28 inches of water per acre. However,
water use varies greatly in sorghum, depending on
the final yield, the maturity of the hybrid, planting
date and weather conditions.   For this reason, prior
to planting, the soil profile should be filled to 24
inches deep if a grower desires a maximum yield.
Water needs
at different growth stages
Water needs for sorghum vary according to the
different plant stages — different amounts are used
in the seedling development phase, the rapid
growth and development stage, and the bloom to
harvest phase (Fig. 1).
Figure 1. Water needs for sorghum rise sharply at the
rapid growth stage, peak during the boot stage and then
drop off afterward.
Seedling development
The seedling development stage begins at germi-
nation and ends at about 26 days after planting,
when the plants have five to six mature (fully
expanded) leaves. This early-growth stage does not
directly affect the number of seeds produced, but it
does set the direction of development.
Although water management is not critical dur-
ing the seedling development period, minor stress
does affect future growth, plant size and yield
potential.
During the seedling stage when the soil is not
shaded, more moisture is lost through soil evapora-
tion than by transpiration from leaves. To minimize
moisture losses from the soil, it is important that
you adopt water-conserving practices, such as:
• Residue management
• Conservation tillage           
• Narrow-row spacing
• Good weed control, and
• Proper planting date for rapid canopy estab-
lishment
Rapid growth
and early reproductive phase
The need for water is extremely critical during
the rapid growth stage and before the reproductive
stage. If the plants are water stressed during the
rapid growth stage, it does not matter what steps a
grower takes afterward — the number of flowers
has already been determined and yield will be
reduced.
After seedling development, water needs begin
to increase as the leaves enlarge and expand.
Because leaves are the part of the plant that collect
energy from the sun, growers should adopt produc-
tion practices (such as those listed above) that
encourage early leaf development.
About 40 days after planting, the total number of
leaves has been determined and one-third of the
total leaf area has developed. During this period,
the growing point changes from vegetative to
reproductive, and the seed panicle begins to form
inside the stalk.
During the next 30 to 35 days, the immature
leaves continue to grow and the number of ovules
that will develop into seed are formed until the flag
leaf (final leaf) emerges and the plant begins to
boot. The size of the panicle and number of seeds
are determined between day 35 and 65 by adequate
water, fertility and photosynthate production. Root
formation is completed and the panicle (head) is
2
.4
.3
.2
.1
7
Leaf
Rapid
growth
Boot Bloom
Grain
fill
Drying
24 50 70 80 120
Days after planting
D
ai
ly
 w
at
er
 u
se
 in
 in
ch
es
Estimated Daily Water Use for Grain Sorghum
visible in the bottom of the plant inside the stalk.
The demand for water is extremely critical dur-
ing this stage because the potential head size has
already been determined before head exertion
begins. The goal is to limit moisture stress during
the rapid growth phase so that a robust plant struc-
ture and full panicle have been produced. 
Growers should not wait too long to irrigate, else
production will suffer. Water use will be about 0.2
to 0.3 inch per acre per day. Up to bloom, sorghum
will use about 8 to 10 inches and any moisture
stress during this period will reduce the yield
potential.
Bloom to harvest
(reproductive stage) 
In the next stage, the plant develops from bloom
to physiological maturity, which is when the seeds
are fully developed and no further weight is added.
This phase requires about 45 days to complete.
Sorghum blooms over a 5- to 9-day period. During
this time, the proteins and photosynthates that are
produced and stored in the leaves are moved into
the developing grain.
During the period just before bloom and until
early grain fill, sorghum will use about 0.35 inch of
water per day, declining to 0.1 inch a day when the
grain is dry. Anything that reduces leaf function —
such as leaf loss, water or nutrient stress, or disease
or insect damage — will eventually reduce yield.
Growers should time the final irrigation to carry
the crop from the last irrigation to black layer, or
physiological maturity. Any additional irrigation
just before and after this point is wasted. From
physiological maturity until harvest, the crop is just
drying down. By harvest, the plant will have
absorbed about 35 pounds of nitrogen and 11
pounds of phosphate for each 1,000 pounds of grain
and stover produced. After the initial 8 to 10 inch-
es of water to reach bloom, each additional 1 inch
of water will produce 350 to 425 pounds of grain,
bringing the total to 28 inches of water for a 7,000-
pound yield. 
Furrow irrigation
Furrow irrigation is best timed according to the
plants’ stage of growth. Furrow irrigation is not as
exact as is sprinkler irrigation. If furrow irrigation
is managed well, most water applications will be
about 3 to 4 inches per irrigation.
A good guide is to apply irrigations at key growth
stages if there is no rain and additional soil mois-
ture is needed: 
1.  If the soil profile is full at planting, the stored
soil moisture should supply the water require-
ments until the first irrigation at the repro-
ductive stage.
2.  The onset of the reproductive stage is 30 days
after planting. One 4-inch irrigation will last
the 25 days until flag leaf. 
3. At flag leaf or boot stage, two 3-inch irrigations
about 2 weeks apart will last until soft dough
in the grain fill period. 
4. The last irrigation will maximize yield, but is
generally not economical and does not pay for
the water. One 3- or 4 inch-irrigation is needed
at soft dough to complete grain fill, which takes
about 45 days from bloom to reach black layer.
Using this schedule, the appropriate amount of
irrigation water will be applied during each grow-
ing period if rainfall is not received. If those
amounts are totaled for the entire growing period,
the amount need by the crop will approximate the
following: 
6 - 8 inches  rainfall or pre-irrigation to fill
the soil profile if totally dry
+ 4 inches 30 days after planting
+ 6 inches in two 3-inch irrigations at flag
leaf or boot stage
+ 3 inches at soft dough
= 19 - 21 inches of total water
The 19 to 21 inches is the amount of water need-
ed to produce a crop without stress. The total
amount needed will vary somewhat, depending on
weather conditions such as heat, low humidity,
cloud cover and wind.   
How much replacement water
is needed?
The amount of water a crop uses is known as
evapotranspiration (ET), which is the water lost
through a combination of two processes: evapora-
tion, which is the water removed from the soil, and
transpiration, which is the water removed from the
plant leaves. The amount (in inches) of water used
by a crop in a day is called daily ET. 
ET varies by weather conditions (such as wind,
humidity, temperature, cloud cover or solar radia-
tion) and by plant characteristics (such as canopy
3
closure). Because it is related to the leaf surface
area, smaller plants transpire less than do larger
plants, and ET is lower.
Growers can minimize evaporation from the soil
by:
• Spacing the plants equally in narrow rows.
Narrow-row crop production reduces the
amount of bare soil, which loses more mois-
ture through evaporation than do shady and
mulched soil surfaces. 
• Leaving crop residues, which can reduce soil
evaporation by 1 to 3 inches during the season.
Irrigation scheduling based
on potential evapotranspiration
Researchers have developed a simple way for
growers to calculate the water requirements of their
crops. First, the water requirements of a standard
plant were developed to use as a reference. That
plant’s water requirements are referred to as PET
(potential evapotranspiration).
Growers can now use PET to calculate the esti-
mated water needs of their crops. To determine the
amount of water being used by their crop, growers
multiply the PET by the crop coefficient (Kc) for the
specific crop being grown and for that crop’s
growth stage. For sorghum, the crop coefficients in
the North High Plains are listed by stage of growth
in Table 1. Researchers at the Uvalde Research and
Extension Center are working to determine the
sorghum crop coefficients for South Texas. 
PET can be obtained for different parts of the
state on the Internet at http://texaset.tamu.edu/
where weather stations across much of south Texas
will give producers weather information to calcu-
late PET for a day or several days. 
Please note that the dates listed are provided
only as a general guide, as crop growth rate is
affected by many factors, including location, vari-
ety, current weather and soil moisture conditions.
How to Use PET
To calculate the water requirements of your
crop, multiply the PET by the crop coefficient using
the following equation:
PET  x  Kc  =  Crop water requirements
PET is the sum of daily PET over the period of
interest, such as the 3-day or weekly total. 
Kc is the crop coefficient for the current stage of
crop growth.
Example 1: The 5-day PET total is 1.32 inches.
Your sorghum is in the “heading” growth stage.
What are the water requirements? (Note: From
Table 10, the “heading” crop coefficient is 1.10.)
1.32 inches    x    1.10    =    1.45 inches
Thus, to irrigate the sorghum adequately during
this period, apply 1.45 inches to replace the water
used by the sorghum in the past 5 days. 
Adjusting for
irrigation system efficiency
If your irrigation system is inefficient, you may
need to compensate for it by increasing the amount
of water you irrigate. See Table 2 for the typical effi-
ciency ranges of on-farm irrigation systems. To
adjust for irrigation system efficiency, use the fol-
lowing equation:
PET  x  Kc  =  Eff  =  Irrigation water requirements
Eff is the overall efficiency of the irrigation sys-
tem.
4
Table 1. Sorghum crop coefficients in the North High
Plains.
Growth Crop Days After
Stage1 Coefficient (Kc) Planting2 
Seeding 0.40 3 - 4
Emergence 0.40 5 - 8
3-leaf 0.55 19 - 24
4-leaf 0.60 28 - 33
5-leaf 0.70 32 - 37
GPD 0.80 35 - 40
Flag 0.95 52 - 58
Boot 1.10 57 - 61
Heading 1.10 60 - 65
Flower 1.00 68 - 75
Soft dough 0.95 85 - 95
Hard dough 0.90 195 - 100
Black layer 0.85 110 - 120
Harvest 0.00 125 - 140
1Sorghum will bloom at different times, depending on location,
planting date and maturity of the variety.
2The days after planting are for a medium-early to medium-late
variety.
5
Example 2: You are irrigating with a low-pressure
center pivot. You estimate that your overall system
efficiency is 85 percent. What are the irrigation
water requirements for the sorghum in Example 1?
1.32 inches  x  1.10  =  0.85  =  1.71 inches
You will need to irrigate 1.71 inches to meet the
plants’ water requirements for that period.
Table 2. Typical overall on-farm efficiencies for various
types of irrigation systems.
Overall 
System Efficiency
Surface 0.50 - 0.80
Common 0.50
Land leveling and water 0.70 - 0.80
volume per row meeting
design standards
Surge 0.60 - 0.90 1
Sprinkler 0.55 - 0.75 2
Center Pivot 0.55 - 0.90 2
LEPA 0.90 - 0.95
Drip/Trickle 0.80 - 0.90 3
1 Surge has been found to increase efficiencies 8 to 28% over
non-surge furrow systems.
2Higher efficiencies are for low wind conditions.
3Trickle systems are typically designed at 80 to 90% efficiency.
Adjusting for rainfall and
soil moisture
Rainfall reduces the amount of irrigation water
needed to meet plant requirements. However, not
all rainfall can be used by plants and crops. Some
of the rainfall will be lost to evaporation from the
top 2 to 3 inches of soil, runoff and deep percola-
tion (water moving below the root zone), depending
on such factors as soil type and slope, soil moisture
levels and the duration and intensity of rainfall.
In irrigation scheduling, the term effective rainfall
refers to the part of the rainfall that can be used by
plants — the part that infiltrates into and is stored in
the root zone. Growers must estimate the effective
rainfall for each field and for each rainfall. General-
ly, do not record rainfall of less than 1/4 inch because
it evaporates so quickly. Then subtract the amount
of effective rainfall from the irrigation requirement
determined with Equation 1 or 2.
You may use soil moisture monitoring devices to
determine soil moisture levels and the date to
restart irrigations after rains. For more information
on this procedure, see Texas Cooperative Extension
publications B-1670, Soil Moisture Management, and
B-1610, Soil Moisture Monitoring.
Common mistakes
Growers need to avoid these common mistakes
affecting water usage: 
• Waiting too long to put on the first irriga-
tion. The head begins to form about 35 days
after planting. If the plant is stressed during
this period, the number of seeds per head will
be reduced.
• Irrigating too late. Do not irrigate after the
hard dough stage. Also do not irrigate after the
plants have reached physiological maturity,
which is 45 days after flowering or at black
layer. After that point, the individual seed’s
“umbilical cord” is sealed off and stops func-
tioning. It will not gain any more weight after
this event, which occurs at about 30 percent
moisture.
• Over-planting. For irrigated production, do
not exceed 70,000 to 80,000 established plants
per acre; dryland production should not
exceed 50,000 to 60,000 established plants per
acre. Over-planting reduces head size, increas-
es the chance of charcoal rot and lodging,
increases plant competition, and increases
water use with little increase in yield. 
Proper irrigation management is critical for prof-
itable yields. If you pay attention to timely and ade-
quate irrigation, you can keep costs to a minimum
while maximizing production. 
Produced by Agricultural Communications, The Texas A&M University System
Extension publications can be found on the Web at: http://tcebookstore.org
Educational programs of Texas Cooperative Extension are open to all people without regard to race, color, sex, disability, reli-
gion, age or national  origin.
Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8,
1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Chester P. Fehlis,
Director, Texas Cooperative Extension, The Texas A&M University System.
2.5M, New


Texas A&M University

Not a member yet

TAMUQ Library Collection November 12, 2024

Sampling for Bacteria in Wells

Shock Chlorination of Wells

Land Application of Drilling Fluids: Landowner Considerations

Phosphorus Fertility in Wheat: It is not a question of how much, but also where

Managing Crop Nutrients Through Soil, Manure and Effluent Testing

Athletic Fields and Water Conservation

Irrigating Sorghum in South and South Centeral Texas

Forage Bermudagrass: Selection, Establishment and Management

2012 Texas Wheat Variety Trial Results

47,493

136,879