OAKTrust Digital Repository (Texas A&M Univ)

Provin, Tony

Pitt, J.L.

If your soil has a high salinity content, the plants growing there will not be as vigorous as they would be in normal soils. Seeds will germinate poorly, 
if at all, and the plants will grow slowly or become 
stunted. If the salinity concentration is high enough, 
the plants will wilt and die, no matter how much you 
water them.
Routine soil testing can identify your soil’s salinity 
levels and suggest measures you can take to correct 
the specific salinity problem in your soil.
Salinity and salt
The terms salt and salinity are often used inter-
changeably, and sometimes incorrectly. A salt is sim-
ply an inorganic mineral that can dissolve in water. 
Many people associate salt with sodium chloride— 
common table salt. In reality, the salts that affect both 
surface water and groundwater often are a combina-
tion of sodium, calcium, potassium, magnesium, chlo-
rides, nitrates, sulfates, bicarbonates and carbonates 
(Table 1).
These salts often originate from the earth’s crust. 
They also can result from weathering, in which small 
amounts of rock and other deposits are dissolved over 
time and carried away by water. This slow weather-
ing may cause salts to accumulate in both surface 
and underground waters. The surface runoff of these 
dissolved salts is what gives the salt content to our 
oceans and lakes. Fertilizers and organic amendments 
also add salts to the soil.
Effects of salts on plants
As soils become more saline, plants become unable 
to draw as much water from the soil. This is because 
the plant roots contain varying concentrations of ions 
(salts) that create a natural flow of water from the soil 
into the plant roots.
As the level of salinity in the soil nears that of the 
roots, however, water becomes less and less likely to 
enter the root. In fact, when the soil salinity levels are 
high enough, the water in the roots is pulled back into 
the soil. The plants become unable to take in enough 
water to grow. Each plant species naturally contains 
varying levels of root salts. This is why some plants 
can continue to thrive when others have died.
If the salinity concentration in the soil is high 
enough, the plant will wilt and die, regardless of the 
amount of water applied. Figure 1 shows how the var-
ious salt concentrations affect the movement of water 
from the soil to plants.
Salt buildup
Salinity is of greatest concern in soils that are:
n	 Irrigated with water high in salts;
n	 Poorly drained, allowing for too much evapora-
tion from the soil surface;
n	 Naturally high in salts because very little salt 
leaches out;
n	 In areas where the water table (the level or depth 
to free-flowable water in the soil) is shallow; or
n	 In seepage zones, which are areas where water 
from other locations (normally up slope) seep 
out.
The major source of salinity problems is usually 
irrigation water. This is a gradual process—the salts 
must accumulate over time before any effects are 
E-60 
3-12
Managing Soil Salinity
Tony Provin and J.L. Pitt*
*	Professor	and	Extension	Soil	Chemist,	Extension	Program	Specialist;		
The	Texas	A&M	University	System.
Table 1. Typical salts found in irrigation water.
	 Common Chemical Chemical
 Name Name Formula
Table	salt	 Sodium	chloride	 NaCl
Glauberís	salt		 Sodium	sulfate	 Na2SO4
Baking	soda	 Sodium	bicarbonate	 NaHCO3
Epsom	salt	 Magnesium	sulfate	 MgSO4
Gypsum	 Calcium	sulfate	 CaSO4	2H2O
Street	salt	 Calcium	chloride	 CaCl2	2H2O
Muriate	of	potash	 Potassium	chloride	 KCl
Muriate	of	sulfate	 Potassium	sulfate	 K2SO4
2
seen. Fortunately, plants take up many salts in the 
form of nutrients. But when more salt is added to the 
soil than is removed, the plants will eventually be 
affected. 
In some soils, irrigation and rainwater move 
through the soil to leach out the salinity. Leaching 
occurs when water moves materials (such as salts or 
organic materials) downward through the soil. Several 
soil factors can inhibit leaching: a high clay content; 
compaction; a very high sodium content; or a high 
water table. Salt problems occur when water remains 
near the surface and evaporates, and when salts are 
not dissolved and carried below the root zone. 
Soils naturally high in soluble salts are usually 
found in arid or semi-arid regions, where salts often 
accumulate because there is not enough rainfall to dis-
solve them and leach them out of the root zone. Salt 
spray near coastlines can also cause salts to build up 
in the soil. 
In areas with shallow water tables, water contain-
ing dissolved salts may move upward into the rooting 
zone. This occurs by capillary action (similar to the 
way a wick works), where evaporation serves as the 
suction of water up through the soil (Fig. 2). Water 
moves the farthest through finer clay and clay loam 
soils; it moves less in medium-textured soils (loams); 
and least in coarser, sandy soils.
Soil testing
To determine the type of problem in your soil, col-
lect a soil sample and have it tested. The best indica-
tor of the extent of a salt problem is a detailed salinity 
analysis, in which water is extracted from a paste. 
This test measures the pH, electrical conductivity (EC) 
and water-soluble levels of the soil. EC is a measure of 
the amount of dissolved salts in the paste of soil and 
water.
The Texas Agricultural Extension Service conducts 
several types of soil tests, including detailed salinity 
analyses. For more information on soil testing, see 
Extension publication L-1793, “Testing Your Soil: How 
to Collect and Send Samples” or check the Web site 
of the Soil, Water, and Forage Testing Laboratory at 
http://soiltesting.tamu.edu. The laboratory’s phone num-
ber is (979) 845-4816.
Salt-affected soils
Salt buildup can result in three types of soils: saline, 
saline-sodic and sodic. Saline soils are the easiest to 
correct; sodic soils are more difficult. Each type of soil 
has unique properties that require special manage-
ment.
Figure 1.	Increased	salts	in	root	zone	can	result	in	decreased	water	uptake	by	plant.
3
Saline soils
Saline soils contain enough soluble salts to injure 
plants. They are characterized by white or light brown 
crusts on the surface. Saline soils usually have an EC 
of more than 4 mmho cm-1.
Salts generally found in saline soils include NaCl 
(table salt), CaCl2, gypsum (CaSO4), magnesium sul-
fate, potassium chloride and sodium sulfate. The 
calcium and magnesium salts are at a high enough 
concentration to offset the negative soil effects of the 
sodium salts.
The pH of saline soils is generally below 8.5. The 
normal desired range is 6.0 to 7.0, but many Texas 
soils are naturally 7.5 to 8.3. Leaching the salts from 
these soils does not increase the pH of saline soils.
Saline-sodic soils
Saline-sodic soils are like saline soils, except that 
they have significantly higher concentrations of sodi-
um salts relative to calcium and magnesium salts.
Saline-sodic soils typically have an EC of less than 
4 mmho cm-1, and the pH is generally below 8.5. The 
exchangeable sodium percentage is more than 15 per-
cent of the cation exchange capacity (CEC). CEC is a 
measure of the soil’s capacity to hold cations, namely, 
calcium, magnesium, potassium, sodium, hydrogen 
and aluminum. The higher the CEC, the more prob-
lematic the removal and remediation of the salt prob-
lem.
Water moves through these soils much as it does in 
saline soils, although the steps for correcting saline-
sodic soil are different. Simply leaching the salts from 
this soil will convert it from saline-sodic to sodic soils.
Sodic soils
Sodic soils are low in soluble salts but relatively 
high in exchangeable sodium. Sodic soils are unsuit-
able for many plants because of their high sodium 
concentration, which may cause plant rooting prob-
lems, and because of their high pH, which generally 
ranges from 8.5 to 12.0.
These high sodium levels disrupt both the chemi-
cal and physical composition of soil clays. As a result, 
the soil surface has low permeability to air, rain and 
irrigation water. The soil is sticky when wet but forms 
hard clods and crusts upon drying.
This phenomenon may not occur in very sandy soils 
because they lack clay content. 
Salt problems
When salts accumulate in soils, problems arise for 
two main reasons: the soil becomes less permeable, 
and the salt damages or kills the plants.
The first problem is associated with the soil struc-
ture. In sodic soils, high levels of exchangeable sodium 
cause the individual sand, silt and clay particles to be 
separated and not clumped together into larger par-
ticles.
This dispersion makes the soil tight and impervi-
ous, so that it allows little air, rain or irrigation water 
to permeate into the soil. Therefore, the plants may 
not receive enough moisture and oxygen to grow. Salts 
may accumulate on the soil surface because they can-
not leach out of the root zone.
Plants can also be damaged by salt effects or toxic-
ity. In saline and saline-sodic soils, high concentrations 
of soluble salts reduce the amount of available water 
for plants to use. High levels of sodium can be toxic to 
certain plants. 
Also, the very high soil pH in high-salt soils greatly 
changes the nutrients available to the plants. These 
Figure 2.	Leaching	is	the	process	of	adding	sufficient	water	
to	the	soil	to	dissolve	salts	and	carry	them	out	of	the	root	
zone.
a.		When	the	salt	concentration	in	the	soil	is	less	than	that	
in	the	plant,	water	moves	from	the	soil	into	the	plant.
b.		When	the	salt	concentration	in	the	soil	is	equal	to	that	of	
the	plant,	there	is	no	net	movement	of	water.
c.		When	the	salt	concentration	in	the	soil	is	greater	than	
that	of	the	plant,	water	moves	from	the	plant	into	the	
soil.					
4
high pH levels change the ionic form of many plant 
nutrients to forms that make them unavailable to 
plants.
Correcting salt-affected soils
Salt-affected soils can be corrected by:
n	 Improving drainage
n	 Leaching
n	 Reducing evaporation
n	 Applying chemical treatments
n	 A combination of these methods
Improving drainage: In soils with poor drainage, 
deep tillage can be used to break up the soil surface 
as well as claypans and hardpans, which are layers 
of clay or other hard soils that restrict the downward 
flow of water. Tilling helps the water move downward 
through the soil.
While deep tillage will help temporarily, the parts 
of the soil not permanently broken up may reseal. 
Leaching: Leaching can be used to reduce the salts 
in soils. You must add enough low-salt water to the 
soil surface to dissolve the salts and move them below 
the root zone. The water must be relatively free of 
salts (1,500 - 2,000 ppm total salts), particularly sodi-
um salts. A water test can determine the level of salts 
in your water.
Leaching works well on saline soils that have good 
structure and internal drainage. To leach a highly 
saline soil, you may need to apply as much as 48 acre-
inches of water. An acre-inch is the volume of water 
that would cover 1 square acre to a depth of 1 inch 
(27,152 gallons).
Testing is often needed to determine how much 
water is needed to correct a particular soil. The test-
ing laboratory can advise on how much water to add. 
After an application, the soil often must be retested to 
determine whether enough salts were leached out.
Highly saline soils should be leached using several 
applications, so that the water can drain well. Here 
again, drainage can be a problem. If the water cannot 
infiltrate the soil, the salts cannot be dissolved and 
leached out of the soil.
Reducing evaporation: Applying residue or mulch 
to the soil can help lower evaporation rates.
Chemical treatments: Before leaching saline-sodic 
and sodic soils, you must first treat them with chemi-
cals, to reduce the exchangeable sodium content. To 
remove or exchange with the sodium, add calcium in 
a soluble form such as gypsum. Again, the laboratory 
analysis can determine how much calcium to add.
After the calcium treatment, the sodium can then 
be leached through the soil along with the other sol-
uble salts. Gypsum is the most common amendment 
used to correct saline-sodic or sodic soils that have no 
calcium source such as gypsum or free carbonates. 
These are available at garden centers and agricultural 
supply stores. Another amendment, calcium chloride, 
is used in some places, but it is seldom available in 
most areas.
Many soils in the southern and western two-thirds 
parts of Texas contain significant concentrations of 
free limestone, which contains calcium carbonate. 
Unfortunately, these calcium sources do not dissolve 
in soils with high pH and therefore cannot help lower 
sodium levels.
If your soil contains free carbonates, you can add 
acids to it to form gypsum, which will react with the 
soil to remove the exchangeable sodium. Add sulfuric 
acid, sulfur, iron sulfates and aluminum sulfate, which 
will react in the soil to produce acid. The acid will 
then react with the calcium carbonates (limestone) to 
form calcium sulfate (gypsum), water and carbon diox-
ide. The acidity may also displace some of the sodium.
Table 2 lists typical amendments used to correct 
salt-affected soils. Although all of these amendments 
work, to use them you must know the amount of reac-
tive limestone present. In general, gypsum is the safest 
and most effective material.
Steps for treating sodic 
and saline-sodic soils 
Correcting saline-sodic and sodic soils is a slow pro-
cess that must be carried out in steps:
1. Treat the surface first, then continue to the lower 
depths.
2. Apply an amendment to the soil surface and disk 
it in.
3. Add 10 to 12 inches of water. As when correct-
ing saline soils, you must add enough water to 
dissolve as well as maintain the calcium concen-
trations in solution and to move the salts and 
sodium through the soil.
However, do not add so much water that it remains 
ponded on the soil surface for extended periods.
Generally, this process must be repeated over time. 
A good goal is to remove the sodium to a minimum 
depth of 3 to 4 feet.
Test the soil periodically to pinpoint potential salin-
ity problems and to measure your progress in correct-
ing salt-affected soils.
The amount of amendment you need to correct 
saline-sodic and sodic soils is based on the amount of 
sodium in the soil. Several other factors also influence 
the amount applied: the leaching rate, the solubility 
and reaction rates of the amendments, and the conver-
sion of free carbonates to gypsum.
If you take steps early, correcting the soil will be 
easier and less expensive, and it will have less nega-
tive impact on soils and plants.
Table 2. Typical soil amendments for correcting saline and saline-sodic soils1 
    Approximate No. Pounds 
    to Supply 1,000 Pounds 
 Amendment Chemical Formula Purity, %2 of Soluble Calcium3
Gypsum	 CaSO4	2H2O	 100	 4,300					
Calcium	chloride	 CaCl2	2H2O	 100	 3,700					
Sulfur4	 S	 100	 800		
Sulfuric	acid4	 H2	SO4	 95	 2,600					
Iron	sulfate4	 FeSO4	7H2O	 100	 6,950					
Aluminum	sulfate4	 Al(SO4)318H2O	 100	 5,550					
Lime-sulfur	solution4,5	 Calcium	polysulfide	 24	 3,350					
1	From	USDA	Agriculture	Information	Bulletin	No.	195.	(1)
2	With	purities	less	than	these,	additional	material	will	need	to	be	supplied.
3	Assumes	free	carbonates	present	to	react	with	the	amendments	that	contain	no	calcium.
4	Sulfur	amendments	are	only	used	in	soils	that	contain	free	calcium	carbonates.
5	Expressed	as	sulfur	content.


Managing Soil Salinity

Dorsett, Donald J.

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Texas Agricultural Extension Service
The Texas A&M University System
Pasture Management for
Beef  Cattle Production
Donald J. Dorsett
Associate Professor and Extension Forage Specialist
Texas Agricultural Extension Service • Edward A. Hiler, Interim Director • The Texas A&M University System • College Station, T exas
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.
m m m m m m m m
Pasture management for beef cattle production involves
a multiple of choices. Management is defined as the act
or art of managing. Manage is defined as to alter by
manipulation.  The question then becomes how do we
alter by manipulation for beef cattle production?
The first management choice is to use native forages
(rangeland) or to use improved pastures.  This may or
may not be a choice.  The existing forage resource on
the land may force the use of what is there.
Native forages can provide a wide range of plants for
livestock use, however, so require several acres per ani-
mal unit.  In reality, many rangeland managers do not
manage the pastureland, they simply graze the forage
until it is gone then feed until more forage grows. Other
managers use brush-weed control and grazing manage-
ment for maximum sustained forage production.
Improved forages are generally managed in monocul-
ture stands.  All respond to fertility with increased pro-
duction that results in less acreage per animal unit. Im-
proved forages for pastures are classed as: (1) warm-
seasoned perennial grasses, (2) cool-season perennial
grasses, (3) warm-season annual grasses, (4) cool-sea-
son annual grasses and, (5) legumes (Table 1).  Warm-
season perennial grasses include such grasses as
bermudagrass, bahiagrass, kleingrass, Old World
bluestems and lovegrasses.  Cool-season perennial
grasses include such grasses as fescue, wheatgrasses,
bromegrasses, and orchardgrasses. These are primarily
grown in  the Texas Panhandle.  Fescue can be found in
some river bottomlands and the Gulf Coast.  Warm-sea-
son annual grasses include crabgrass, sudans, sorghums,
sorghum-sudan hybrids, and millets.  Cool-season an-
nuals include oats, wheat, barley, rye, triticale, ryegrass,
and bromegrass.  Legumes include alfalfa and many clo-
vers that include both warm-season and cool-season
varieties.
Fertility is an  important aspect of improved pastures.
Many improved pasture grasses are selected or bred in a
fertilized regime so will not perform as expected if fer-
tilizer is not a part of the program.  A planned fertility
program will allow the pasture to produce as expected
and provide an abundant quality forage.  The point
should also be made that fertility for pasture production
and hay production is not the same.  In a hay meadow,
fertility is applied for maximum production in a short
time, the hay is harvested and nutrients in the forage is
stored in the hay. There is very limited recycling of nu-
trients. Fertility in a pasture is expected to maintain pro-
duction over the growing season and has recycling of
nutrients from lost and trampled plant parts and animal
excreta.  For this reason, pasture fertility is reduced com-
pared to hay production.  Interpolation of data from the
Angleton Experiment Station, the Overton Research and
Extension Center and the Louisiana Brown Loam Ex-
periment Station leads to the conclusion that between
175 and 200 lbs. of nitrogen per cow-calf unit per year
is needed.  This assumes that phosphorus and potas-
sium are adequate or applied according to soil test (Table
2).
Weed control is an aspect of pasture management that
pays big dividends if required.  If enough weeds are
present to cause a reduction in forage production, most
research shows that for each pound of weeds controlled,
there is a gain of at least 1 pound of grass.  Some work
shows a return of up to 7 pounds of grass for 1 pound of
weed controlled.  While cattle will consume most weeds
when they are very small, they rarely control weeds by
grazing in normal pasture systems.  When heavy weed
pressure is evident in a pasture, weed control will pay
big dividends in forage production (Table 3).
Table 1. Relationship between percent digestible dry matter content of several classes of
forage and the nutrient requirement  of cattle
80
70
60
50
Warm Season Warm Season Cool Season Cool Season Legumes
Perennial Annual Perennial Annual
Grasses Grasses Grasses Grasses
Note:   Research Monograph 6, January 1976, Principles of Grazing Management by M. E. Riewe
440-lb. stocker
ADG - 1.7 lbs.
Dry, pregnant cow
gaining condition
Grazing management is a factor in pasture forage pro-
duction that is largely overlooked and controversial.
Grazing management is directed at more efficient utili-
zation of a forage resource than providing a rest period
for forage recovery.  Most research efforts have shown
that individual animal performance suffers to some de-
gree in rotational grazing systems but forage produc-
tion and utilization improves.  Many advocates of the
rapid rotation grazing point out an increased carrying
capacity resulting from their grazing management.  Re-
search is documenting such things as increased efficiency
of nutrient recycling, decreased weed control needs and
increased carrying capacity as a result of rapid rotation
grazing.  A rule of thumb that applies in grazing man-
agement is that the manager will make or break the sys-
tem (Tables 4 and 5).
Table 2. Average production due to nitrogen fertilization (from research in Texas, Alabama,
Georgia, Mississippi, and Louisiana).
TONS OF DRY FORAGE PER ACRE
Nitrogen/Acre * Common Coastal
(Pounds) Bahia Bermuda Bermuda Klein 75
0 1.75 1.00 1.33 1.50
50 1.84 1.20 1.46 2.00
100 2.87 2.20 3.61 --
150 3.33 -- -- 3.00
200 3.95 -- 4.78 --
300 4.65 -- 4.73 3.20
400 -- -- 5.80 --
600 -- -- 6.50 --
Table 3. Forage Response to weed control and fertilization methods in a dry (1990) and wet
(1991) season
Yield 1990 Yield 1991
Treatment (lbs . DM/ac) (lbs. DM/ac)
Early herbicide - fertilized 2142 8322
Early herbicide - unfertilized 1330 4988
Late herbicide - fertilized 881 7610
Late herbicide - unfertilized 477 4989
Shredding - fertilized 577 5088
Shredding - unfertilized 341 4787
Fertilizer only, no herbicide 645 2587
Control 377 1385
Table 4. Comparison of continuous and short-duration grazing methods of ryegrass-clover
pastures
Item Continuous Short-Duration
Initial Steer wt., lb. 455 455
Stocking Rate, hd/acre 1.5 1.9
Pasture Costs/acre, $ 92 120
Animal Performance
Average daily gain, lb. 2.37 2.29
Gain/acre lb. 675 828
Final steer wt., lb. 905 890
*Adapted from:  G. D. Mooso and D. G. Morrison, Rosepine Research, LA, 1988
Table 5. Comparison of continuous and short-duration grazing methods on bermudagrass
pastures
Item Continuous Short-Duration
Initial Steer wt., lb. 560 560
Stocking Rate, hd/acre 4.0 4.0
Pasture Costs/acre, $ 59 87
Animal Performance
Average daily gain, lb. 0.73 1.01
Gain/acre lb. 412 558
Final steer wt., lb. 663 702
*Adapted from:  G. D. Mooso and D. G. Morrison, Rosepine Research, LA, 1988


Pasture Management for Beef Cattle Production

McFarland, Mark L.

Stichler, Charles

Lemon, Robert G.

Non-Traditional Soil Additives:
Can They Improve Crop Production?
Mark L. McFarland, Charles Stichler and Robert G. Lemon*
Agricultural producers are con-
stantly seeking the most efficient
and economical production sys-
tems.The use of soil additives such
as soil conditioners, soil activators,
wetting agents, soil inoculants,
microbial enhancers, soil stimu-
lants, etc., has been promoted
since at least the late 1800s.
Increasing production costs, espe-
cially for fertilizers, have renewed
producers’ interest in these materi-
als. However, many of these prod-
ucts have not been investigated
scientifically and their benefits are
unproven.
Soil and plant additives may be
classified in a number of different
ways based on criteria such as
intended use or function, applica-
tion method, quantity to be
applied, or origin of the material.
For consistency, most soil scien-
tists and agronomists classify these
products under three main cate-
gories: 1) soil conditioners; 2) soil
activators and biological inocu-
lants; and 3) wetting agents.
In general, soil additives can be
distinguished from fertilizers in
that they usually have little or no
nutrient content. Unlike fertilizers,
additives are commonly not mar-
keted with, nor are they required
to provide, a guaranteed analysis
(e.g., 10-34-0 or 32-0-0). Instead,
manufacturers often suggest that
adding these materials to the soil
will enhance crop production by
improving water and/or nutrient
availability and uptake by plants.
These enhancements are generally
said to occur when standard fertil-
izer applications are made to the
crop at recommended or near rec-
ommended levels, although some
additives claim to replace or signif-
icantly reduce the need for fertiliz-
ers.
Most traditional soil amend-
ments and commercial fertilizers
have been tested extensively
through research trials to docu-
ment both their benefits and limi-
tations. Unfortunately, adequate
research funds often are not avail-
able to investigate the many new
products being marketed, includ-
ing non-traditional additives.
Nevertheless, consumers should be
aware of the types of products
available and have some knowl-
edge of their potential to benefit
crop production.
Soil Conditioners
Soil conditioners usually are
defined as materials that improve a
soil’s physical condition or struc-
ture and, in turn, the soil’s aeration
and water relationships. Certainly,
maintaining and/or improving soil
structure is highly desirable in
crop production. Adding organic
matter to the soil is the most com-
mon method for improving soil
structure. Traditional additives
include crop residues, livestock
manures and sewage sludge. Non-
traditional soil conditioners
include both organic and inorganic
products such as:
1) Composted organic materials
which also may be supple-
mented with inorganic mate-
rials such as unprocessed
rock phosphate or ground
limestone. The composition
of these materials is quite
variable. Such additives may
be marketed as liquid extracts
of livestock manure or other
organic residues.
2) Mined mineral deposits that
are unprocessed except for
grinding. Again, the composi-
tion of these materials can be
highly variable, but may
include granite, glauconite 
(a mineral high in unavailable
potassium), and gypsum or
sand.
3) Mined humates or humic
acids. These are prehistoric
organic deposits in the
advanced stages of transfor-
mation into coal which are
normally discarded during
mining. Liquid humates also
have been marketed and are,
presumably, a concentrate of
humic acids.
4) Various inorganic solids such
as evaporated sea water or
sulfates, which may be com-
bined with organic extracts
of materials such as kelp (sea
weed) or whey.
Humates and/or humic acid are
good examples of  non-traditional
soil conditioners, and a number of
*Assistant Professor and Extension Soil Fertility
Specialist,Associate Professor and Extension
Agronomist, and Assistant Professor and
Extension Agronomist - Peanuts and Cotton,
The Texas A&M University System.
L-5202
4-98
research trials across the United
States have evaluated their effects
on soil properties and crop
growth. Studies conducted in
Kansas (Table 1) showed that
humate did not significantly
improve corn grain yields over a 3-
year period (1). Similar results
were observed in research on a
related material called leonardite,
an organic, coal-like deposit report-
edly high in humic acid (2).
Research in Illinois (3), North
Dakota (2) and Canada (4) showed
no significant improvement in
yields of corn grain, corn silage,
wheat, barley and field beans when
various soil conditioners were
applied alone or in combination
with commercial fertilizer. In con-
trast, most studies showed consis-
tently improved yields with the
addition of irrigation water and tra-
ditional commercial fertilizers.
Soil Activators
Soil activators are marketed on
the basis that they stimulate exist-
ing soil microbes or inoculate the
soil with new beneficial organisms.
Some manufacturers suggest that
such products may improve soil
physical properties (increase struc-
ture, reduce compaction), increase
fertilizer and soil nutrient uptake,
improve crop yields and/or quality,
correct soil “toxicities” (such as
salinity), and provide disease and
insect resistance (5). Most soil
microbiologists agree that to signif-
icantly increase the activity of soil
microbes for more than a few
hours, a minimum of several hun-
dred pounds of organic material
must be added to the soil.
However, these products often are
applied at rates of only a few
pounds per acre, which may add as
little as 1 pound of microbes to
soil that already contains  2,000 to
4,000 pounds of microbes per acre
(6).
Numerous studies have been
conducted across the United States
to evaluate various soil activators.
In general, these studies have
shown no significant beneficial
effects of these products on crop
yields or quality. Table 2 presents
results of field studies conducted
in Texas using two soil activator
products (5). In both fertilized and
unfertilized plots, neither product
increased yields of grain sorghum
or cotton above the check plot.
Laboratory evaluations of these
products also indicated that they
did not increase the numbers or
activity of soil microbes and thus,
would not be expected to increase
the rate or extent of crop residue
decomposition.
Other field trials using these
two products were conducted on
forages, peanuts, rice, soybeans and
tomatoes by researchers in Texas,
Alabama, Louisiana and Oklahoma
(5).These studies consistently indi-
cated that neither product signifi-
cantly affected  yields of the vari-
ous crops under the different soil
and climatic conditions. This work
is extremely important, particularly
because it included 22 different
soil series ranging from fine sands
to clays (pH range 4.8 to 8.4), and
because the work was continued
at the same locations over a 2- to 3-
year period to verify results.
Certainly, inoculation to stimu-
late the development of certain
types of beneficial microogran-isms
is not uncommon. In certain
sewage treatment processes and
composting operations, a portion
of the treated material may be used
to provide “seed” organisms to
unprocessed material. An example
in agriculture is inoculation of seed
with Rhizobium bacteria to pro-
mote good nodulation in legume
crops. However, these biological
Table 1. Effects of humate on yields of irrigated corn.1
Grain yield (bu./acre)
Treatment 1978 1979 1980 Average
Control (no fertilizer) 211 152 170 178
50 lbs. 18-46-0/acre 213 149 177 180
50 lbs. 18-46-0/acre +
250 lbs. humate/acre2 208 162 172 181
50 lbs. 18-46-0/acre +
500 lbs. humate/acre2 210 162 172 181
1Adapted from Lawless et al., 1984 (see References).
2Rate of humate reduced by one-half in 1979 and 1980 applications.
Table 2. Grain sorghum and cotton yields at three locations as affected by application of two soil additives
and fertilizer.1
Sorghum grain yield (lbs./acre) Cotton lint yield (lbs./acre)
Fertility treatment Beeville McGregor Temple McGregor El Paso Lubbock
Unfertilized
Check 175 2057 2218 194 806 290
Product A 140 1854 2233 199 842 301
Product B 217 2036 2202 193 777 310
Fertilized
Check 1110 2543 2237 265 743 393
Product A 900 2514 2352 240 766 370
Product B 1041 2365 2352 240 749 397
1Adapted from Weaver et al., 1974 (see References).
processes have been thoroughly
investigated and the potential ben-
efits reasonably well documented.
Wetting Agents
Wetting agents and surfactants
have long been used in agriculture
in combination with herbicides
and insecticides.Their primary
function is to reduce the surface
tension of water droplets and
improve leaf surface coverage by
foliar sprays. How-ever, many relat-
ed products are marketed on the
basis that they will loosen tight or
compacted soils, improve water
infiltration and retention, enhance
nutrient availability and increase
crop yields. Some research has
shown that certain non-ionic soil
wetting agents do in fact increase
water infiltration rates on
hydrophobic (water-repelling)
soils. However, these materials have
either no effect or an adverse
effect on normal (wettable) soils
(7). Obviously, using results from
one type of soil to predict
response on another soil is often
inappropriate.
Studies in Wisconsin evaluated
the effects of  three wetting agents
on growth and yield of corn, soy-
beans and potatoes (7). Each prod-
uct was evaluated over a 2- or 3-
year period and at up to three dif-
ferent locations. Table 3 shows the
effects of two products on corn
grain yields. Both products were
soil applied according to label rec-
ommendations either preplant or
preemergence. In both studies,
plots were carefully installed to
include checks with and without
fertilizer, in addition to plots
receiving the wetting agents. In
this way, the response of the crop
to fertilizer and to the wetting
agents could be compared.There
was no increase in grain yields
from the addition of wetting
agents, whereas adding commercial
fertilizer significantly increased
corn grain yields compared to the
unfertilized plots. Leaf nutrient
content (N, P, K) also was not
increased by soil application of the
wetting agents.
In several other states, research
on the effects of various wetting
agents on the growth and yields of
potato, soybean, wheat and grain
sorghum (8, 9) has shown no sig-
nificant benefits. However, one
field study in Kansas (10) 
did report a significant yield
response in 1 year of a 4-year
study.
Making Decisions
Soil scientists and agronomists
are often asked to provide recom-
mendtions on the use and effec-
tiveness of new and non-traditional
products. However, many such
products have not been scientifi-
cally evaluated. As a result, the best
advice that can be given to grow-
ers is to evaluate new products
carefully and insist upon local or
regional research data (not testimo-
nials) demonstrating product effec-
tiveness and value. If there are no
such data, consider conducting
small-scale field trials on your farm.
Figure 1 shows an example layout
for a product trial. The following
factors should be considered when
evaluating new products in farm
and ranch production systems:
1) Use a small area, but one of
adequate size to obtain reli-
able harvest data.
Table 3. Effects of two wetting agents on yields of corn grain over a 
2-year study period.1
Treatment Grain yields (bu./acre)
Nitrogen 
fertilizer rate Product A rate
(lbs./acre) (qts./acre) Year 1 Year 2 Average
0 0 140 126 133
0 2 131 107 119
200 0 183 167 175
200 2 171 155 163
Treatment Grain yields (bu./acre)
Nitrogen
fertilizer rate Product B rate
(lbs./acre) (qts./acre) Year 1 Year 2 Average
0 0 140 126 133
0 1 139 120 130
200 0 183 167 175
200 1 182 166 174
1Adapted from Wolkowski et al., 1985 (see References).
Rep 1 Rep 2 Rep 3
C
h
ec
k
P
ro
d
u
ct
 A
C
h
ec
k
P
ro
d
u
ct
 A
P
ro
d
u
ct
 A
C
h
ec
k
300 - 500 ft.
Width
of
planter
BULK FIELD
}
Figure 1. Example plot layouts for small-scale product or management practice comparisons.
2) Select a field or a location
within a field that is uniform
in soil, slope and management
history.
3) Always compare the plots
receiving the amendment to
check plots that are not treat-
ed.
4) Install at least three or four
replications (separate plots)
of each plot or treatment.
5) Manage all plots in exactly
the same way during the sea-
son, except for the difference
in treatments.
6) Monitor crop growth and
development during the sea-
son to detect treatment differ-
ences.
7) Harvest each plot separately.
Compare the yields for all
replications of a particular
treatment to look at variabili-
ty. If yields for a particular
treatment are not consistent,
it may not perform consis-
tently, or the test site may
have hidden variation.
8) Finally, use the average value
(crop yield or quality) for
each treatment to compare
the different treatments to
each other. Then, evaluate
input costs for each treat-
ment compared to anticipat-
ed returns.
If product and application costs
approach or exceed returns, the
treatment may not be a sound
investment.
The purpose of this publication
is not to suggest that all current
and/or future non-traditional soil
additives are of no value. As new
inventions and new products are
developed they may have the
potential to improve crop yields,
crop quality and/or production
economics. However, proper
product testing and evaluation 
are critical to verifying the poten-
tial benefits of new and unproven
materials.
Farm managers should under-
stand the requirements of their
lands and crops, and thoroughly
assess the benefits and costs associ-
ated with various production prac-
tices. Achieving “maximum eco-
nomic yield” depends upon using
only those inputs which will, with
reasonable certainty, provide a
return on that investment.
References
1. Lawless, J. R., H. D. Sunderman,
F. L. Lamm and L. D. Robertson.
1984. Report of research
results. Supplement 1.
Compendium of research
reports on use of non-tradition-
al materials for crop produc-
tion. NCR-103 Committee.
Iowa State Press, Ames, Iowa.
2. Bauder, J.W. 1976. Soil condi-
tioners - A problem or a solu-
tion?  North Dakota
Agricultural Experiment
Station. Reprint No. 869. Farm
Research. 33:21-24.
3. Egli, D. B. and J.W. Pendleton.
1984. Progress report of agro-
nomic field studies with
leonardite. Compendium of
research reports on use of non-
traditional materials for crop
production. NCR-103
Committee. Iowa State Press,
Ames, Iowa.
4. Elegba, M. S. and R. J. Rennie.
1984. Agrispon: microbial and
elemental analysis and evalua-
tion of its effect on the growth
of wheat, barley, field beans
and corn. Canadian Journal
of Soil Science. 64:621-629.
5. Weaver, R.W., E. P. Dunigan, J. R.
Parr and A.E. Hiltbold. 1974.
Effect of two soil activators on
crop yields and activities of soil
microorganisms in the
Southern United States.
Southern Cooperative Series
Bulletin No. 189. Joint
Regional Publication by the
Agricultural Experiment
Stations of Texas, Alabama,
Florida, Georgia, Kentucky,
Louisiana, North Carolina and
Oklahoma.
6. Miller, R. H. 1978. Ecological
factors which influence the
success of microbiological fer-
tilizers or activators.
Developments in Industrial
Microbiology. 20:335-342.
7. Wolkowski, R. P., K. A. Kelling
and E. S. Oplinger. 1985.
Evaluation of three wetting
agents as soil additives for
improving crop yield and nutri-
ent availability. Agronomy
Journal. 77:695-698.
8. Laughlin,W. M., G. R. Smith and
M.A. Peters. 1982. A multipur-
pose wetting agent,WEX, and a
cultured biological product,
Agrispon, leave potato yields
unchanged. American Potato
Journal. 59:87-91.
9. Fenster,W., G. Randall,W.
Nelson, S. Evans and R.
Schoper. 1978. Effect of WEX
on nutrient uptake and crop
yields. Compendium of
research reports on the use of
non-traditional materials for
crop production. NCR-103
Committee. Iowa State Press,
Ames, Iowa.
10. Sunderman, H. D. 1983. Soil
wetting agents. AES Keeping
Up with Research. No. 73.
Kansas Experiment Station.
Manhattan, Kansas.
Educational programs of the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, 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. Edward A. Hiler, Interim Director, Texas Agricultural Extension
Service, The Texas A&M University System.
3M, New AGR 13-2
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