Soil Testing Equipment

Referent and Standards Product for Soil Testing Equipment

Standard Test Procedures Manual - WET TRACK ABRASION TEST


1.1. Description of Test

This method covers measurement of the wearing qualities of slurry seal, hot sand asphaltmix and sulphur mixes under wet abrasion conditions.


2.1. Equipment Required

Balance 5000 g ± 1 g.
Sieves - Canadian Metric Standard square mesh of size numbers as required by the specifications for the materials being tested. Oven - thermostatically controlled at 60oC ± 1o.
Model C-100 Hobart mixer or equivalent. Metal tray 264 mm by 267 mm by 57 mm deep fitted with four vertical pins near the corners for holding template, sample and distilled water. Template 6 mm thick by 241 mm square with a centre hole 216 mm in diameter complete with four holes in corners to match pins in container tray. 22 to 27 kg grade asphalt roll roofing paper, 240 mm square with four holes to fit pins in metal tray. Water bath thermostatically controlled at 25o C ± 1o.

Abrasive head weighing 2.27 kg coupled to the Hobart mixer with approximately 14 mm free up and down movement in the shaft sleeve. A section of 300 psi reinforced rubber hose 14 mm ID by 31 mm OD and 127 mm in length shall be mounted horizontally on the abrasive head as shown in ASTM Method D3910. Plywood base 305 mm square for transporting and drying of sample in template in the oven.

Suitable prop block and spacers for supporting platform assembly in position during testing. Mixing pan, soft brush, spatula, graduated cylinder, 1800 ml beaker and distilled water. Squeegee or straight edge 305 mm in length. Fumehood, hot plate. Hydraulic press. Steel plate 255 mm square and a 215 mm diameter steel disk, both about 10 mm thick to hold sample while forming in press.


3.1. Sample Preparation

3.1.1. Slurry

Air dry aggregate similar to stockpile average to be used on job. Riffle carefully and complete sieve analysis as per STP 206-1. Place template on roofing paper and tack coat opening with SS1 emulsion. Quarter sufficient amount of dry aggregate required. Weigh approximately 80 gm of aggregate into mixing bowl making sure it is uniformly distributed. Add the predetermined amount of water and mix until particles are uniformly wetted. Finally, add the predetermined amount of emulsion and mix for a period of not less than 1 minute and not more than 3 minutes.

Note: the required water and emulsion content are determined by the consistency test method described in ASTM method paragraph 5.1. A flow of 2 to 3 cm is normally required. Immediately pour sample into template containing smooth roofing paper. Squeegee or straight edge slurry level with the top of the template with minimum amount of manipulation and scrape off excess material and discard

Place specimen in oven at 60o C and dry to constant weight. This usually requires a minimum of 15 hours. Remove sample from oven and allow to cool at room temperature and remove template and weigh. After weighing, place sample in 25o C water bath for 60 to 75 minutes before doing abrasion test.

3.1.2. Hot Sand Asphalt Mix

Dry aggregate and adjust gradation with filler as necessary. Heat aggregate and asphalt cement to desired temperature required and mix at the asphalt content required by the engineer (usually 8 to 12%). Cut square of roofing paper, place on steel plate. Apply tack coat of asphalt to roofing paper and place two template molds on top. Spread 800 g of mix in mold and strike off level with straight edge. Place steel disk over centre of template and place in hydraulic press under 4545 kg for 5 minutes. Weigh mold, mix and paper. Place in oven at 60o C for 4 1/2 hours.
After removing specimen from oven, place in water bath at 25o C for 1 1/2 hours.

3.1.3. Sulphur Mixes

Dry aggregate and riffle sample to approximately 800 g required for testing. Select grade of asphalt cement and heat to approximately 135o C. Heat aggregate and asphalt to 135o C and mix at required asphalt content (usually 8%). Add pelletized sulphur to asphalt mixture based on weight of total mix. This usually requires 16-17% sulphur when the asphalt used is 8 to 8.5 percent range.

Mix well under fume hood until the mixture becomes sloppy. Do not allow the temperature to exceed 150o C as the sulphur will combine with hydrogen to give off sulphur oxide gas. Cut square of roofing paper and place on steel plate. Apply tack coat of asphalt to roofing paper and place two mold plates on top. Spread sulphur mix in mold and strike off level with straight edge. Allow to cool at room temperature for 24 hours and weigh. After curing, place in water bath for 1 1/2 hours

3.2. Test Procedure
Remove specimen, template and roofing paper from water bath and place in metal tray with four pins to secure sample in bottom of tray. Cover sample with 6 mm distilled water at room temperature. Secure metal tray on the Hobart mixer by means of clamps provided and attach the rubber hose abrasion head. Elevate the platform until the rubber hose contacts the surface of sample. This usually requires sufficient pressure for the pin to be at the midpoint of the slotted sleeve. Use prop block to support platform assembly during testing. Operate mixer for exactly 5 minutes ± 2 seconds, at low speed. Remove sample from metal tray and wash off debris using soft brush. Place washed sample at 60o C in oven and dry to constant weight. Remove from oven and allow to cool at room temperature and weigh.


4.1. Collection of Test Results

Record original sample weight after molding and drying to constant weight.

4.2. Calculations

Weigh sample after abrasion and dry to constant weight. Original sample weight minus final abraded weight multiplied by 32.9 expresses the loss in grams per meter square.
(W1 - W2) x 32.9 = g/m2

4.3. Reporting Results

Report the loss in g/m2.


5.1. References
A.S.T.M. D3910
Saskatchewan Highway Technical Report #29.

5.2. General

Slurry showing a loss of more than 800 g/m2 is not acceptable. For asphalt mixes, a loss of 400 g/m2 should not be exceeded. For sulphur mixes no values are available. When pouring sample into template, care should be taken to mix the material uniformly to avoid segregation. Rotate hose after completion of each test and replace if badly worn.

Source : Saskatchewan Highways and Transportation

Soil: The Living Matrix

Around the world, farmers are very intelligent and know the characteristics of soil. They know many  things about  the soil  that scientists do not, and scientists know many  things  that  farmers  do  not,  so  these  two  groups  of  workers  must  work together. This is true of North American, European, and Asian countries. Farming practices are based on empirical experience; some of these practices may not stand up to scientific testing, but others obviously must do.The importance of soil structure as a factor in soil fertility is becoming increasingly clear. If a plant is to grow, its roots must spread so that their delicate structures of root  hairs  can  get  access  to  plant  nutrients. They  also  only  thrive  if  there  is  an adequate supply of water and air. In several countries with plantations of sugarcane, the continuous high yields obtained through irrigation and the extensive application of manure  and  fertilizers  have  created  problems. Chemical  analyzes  of  the  soils
from such areas show that common plant nutrients are still present, but that something has happened to the soil that is interfering with its productivity. At first it was thought  that  the cane  itself  is deteriorating, but  this  is not  likely, as  it propagates vegetatively.  Instead,  unfavorable  conditions  for  beneficial  soil microorganisms may have been produced. The deterioration of  the  soil  structure  seems  to play a direct part in this, because soil microorganisms have an important influence on the soil structure. Soil organic matter – the formation, decomposition, and transformation of which are caused by microorganisms – is of great importance to sustainable soilfertility and soil structure.

More experiments on soil structure and other physical properties of soils, such as permeability,  porosity,  and  moisture  retention  capacity,  are  desirable.  Soil  fertility depends on a large number of complex factors, not all of which are known. Physical properties of the soil are no less important than chemical properties. The clay fraction determines many physical and chemical properties of soils. The properties of clays are determined by their mineralogical compositions. X-ray studies and differential thermal analyses of clays have now become necessities in soil laboratories. The electrochemical properties of clays are fundamentally important to understanding soil behavior. This chapter introduces the various types of soil and their functions, as well as the pollution of the soil with heavy metals, which is detrimental to the health of the soil

Soil Taxonomy and Classification

A soil  taxonomist distinguishes soils partly on  the basis of  the kind of diagnostic horizon(s)  present  in  each  soil.  The  current  soil  taxonomy  (classification)  was adopted  in 1965; a simplified account of  this classification system follows below(see US Soil Survey Report 1972, 1975). Order. This is the most general category. All soils fit into one of ten orders. Suborder. Suborders within a soil order are differentiated largely on the basis of soil properties  and  horizons  resulting  from  differences  in  soil moisture  and  soil temperature. Forty-seven suborders are presently recognized.
Great group. Soil great groups are subdivisions of suborders. The 185 great groups found in the US, and 225 worldwide, have been established largely on the basis of  differentiating  soil  horizons  and  soil  features.  The  soil  horizons  include those that have accumulated clay, iron, and/or humus, and those that have pans
(hardened or cemented soil  layers)  that  interfere with water movement or root penetration.
Subgroup.  Each  soil  great  group  is  divided  into  three  kinds  of  subgroups:  one representing the central (typic) segment of the soil group; a second that has prop-erties that tend toward other orders, suborders, or other great groups (intergrade group); and a  third  that has properties  that prevent  its classification as  typic or intergrade. About 970 subgroups are known in the United States.Family. Subgroups contain soil families, which are distinguished primarily on the basis of  soil properties  important  to  the growth of plants or  the behavior of soils when  used  for  engineering  purposes. These  soil  properties  used  include texture, mineral  reactions  (pH),  soil  temperature,  precipitation  pattern  of  the area,  permeability,  horizon  thickness,  structure,  and  consistency. About  4,500 families have been identified in the United States.Series. Each family contains several (similar) soil series. The 10,500 or more soil series  in  the United States have narrower  ranges of  characteristics  than  a  soil family. The name of the soil series has no pedogenic (i.e., related to soil formation) significance; instead, it represents a prominent geographic name of a river, town,or area near where the series was first recognized. Soil series are differentiated on  the  basis  of  observable  and mappable  soil  characteristics,  such  as  color, texture,  structure,  consistency,  thickness,  reactions  (pH),  and  the  number and  arrangement  of  horizons  in  the  soil  pedon  as well  as  their  chemical  and
mineralization  properties.  Terms  describing  surface  soil  texture,  percentage slope,  stoniness,  saltiness,  erosion,  and  other  conditions  are  called  phases. Mapping units are created by adding phase names to series names. All mappingunits are polypedons. Prior to 1971, soil type was a mapping unit that was used
to denote a subdivision of a series indicating the series name and surface texture. Soil type is no longer official nomenclature; it has been replaced by series phase.

The  prime  land  means  the  best  land.  The  definition  of  prime  land  will  change depending  on  the  use  of  the  land,  and  full  agreement  as  to  exactly  how  “prime” should be defined  is unlikely, even  for a  specific  land use. For  farmland use,  it  is proposed that prime land should meet all the followingrequirements: adequate natu-ral  rainfall  or  adequate  and  good-quality  irrigation water  for  intended  use; mean annual temperature >32°F (0°C) and mean summer temperature >46°F (8°C); lack of excessive moisture – flooding should not occur more often than once every two years; water table should be below the rooting zone; soil should not be excessively acidic, alkaline, or saline; soil permeability should be at least 0.38″  h−1 (1.0 cm h−1) in  the upper 20″  (51  cm);  the  amount of gravel,  cobbles, or  stones  should not be excessive  enough  to  seriously  interfere  with  power  machinery;  any  restricting layer  in  the  soil  should be deep  enough  to permit  adequate moisture  storage  and unhampered root growth, and; the soil should not be excessively erodible.The objectives of soil surveys and taxonomy are to facilitate growth on soils that have never been grown on before, and  to  learn enough about certain soils  to predict how they would respond when irrigated with a specific quantity of irrigation water of known quality. This objective also emphasizes  the  inclusion of a  rational means of transferring technology from one soil to another, interpretations that allow the predition of land use for every soil mapped, and that the survey should serve as a scientific database.  Soil  surveying  has  developed  into  a  specialized  subject. A  survey  report contains information on not only the characteristics of the soil and its profile, but also the  existing  and potential uses of  the  land,  the yields obtained by  the  farmer or by experimental stations under different systems of management, erosion and drainage conditions, and the potential for reclamation or its suitability for irrigation, where these are necessary. Soil maps and survey reports form the basis for planning the utilization of the land, and they have also been found useful in road and building projects.

Drilling Equipment and Operation - Drilling Muds and Completion Systems. Part 1

Drilling Equipment and Operation - Drilling Muds and Completion Systems

A. Drilling Muds and Completion Systems


1.1.1 Drilling Fluid Definitions and General Functions
Results of research has shown that penetration rate and its response to weight on bit and rotary speed ishighly dependent on the hydraulic horsepower reaching the formation at the bit. Because the drilling fluid flowrate sets the system pressure losses and these pressure losses set the hydraulic horsepower across the bit, it can be concluded that the drilling fluid is as important in determining drilling costs as all other “controllable” variables combined. Considering these factors, an optimum drilling fluid is properly formulated so that the flow rate necessary to clean the hole results in the proper hydraulic horsepower to clean the bit for the weight and rotary speed imposed to give the lowest cost, provided that this combination of variables results in a stable borehole which penetrates the desired target. This definition incorporates and places in perspective the five major functions of a drilling fluid.

1.1.2 Cool and Lubricate the Bit and Drill String
Considerable heat and friction is generated at the bit and between the drill string and wellbore during drilling operations. Contact between the drill string andwellbore can also create considerable torque during rotation and drag during trips. Circulating drilling fluid transports heat away from these frictional sites, reducing the chance of premature bitfailure and pipe damage. The drilling fluid also lubricates the bit tooth penetration through the bottom hole debris into the rock and serves as a lubricant between the wellbore and drill string, reducing torque and drag.

1.1.3 Clean the Bit and the Bottom of the Hole
If the cuttings generated at the bit face are not immediately removed and started toward the surface, they will be ground very fine, stick to the bit,and in general retard effective penetration into uncut rock.

1.1.4 Suspend Solids and Transport Cuttings and Sloughings to the Surface
Drilling fluids must have the capacity to suspend weight materials and drilled solids during connections, bittrips, and logging runs, or they will settle to the low side or bottom of the hole. Failure to suspend weight
materials can result in a reduction in the drilling fluids density, which can lead to kicks and potential of a blowout. The drilling fluid must be capable of transporting cuttings out of the hole at a reasonable velocity that minimizes theirdisintegration and incorporation as drilled solids into the drilling fluid system and able to release
the cuttings at the surface for efficient removal. Failure to adequately clean the hole or to suspend drilled solids can contribute to hole problems such as fill on bottom after a trip, hole pack-off, lost returns, differentially stuck pipe, and inability to reach bottom with logging tools. Factors influencing removal of cuttings and formation sloughings and solids suspension include.

• Density of the solids
• Density of the drilling fluid
• Rheological properties of the drilling fluid
• Annular velocity
• Hole angle
• Slip velocity of the cuttings or sloughings

1.1.5 Stabilize the Wellbore and Control Subsurface Pressures
Borehole instability is a natural function of the unequal mechanical stresses and physical-chemical interactions and pressures created when supporting material and surfaces are exposed in the process of drilling a well. The drilling fluidmust overcome the tendency for the hole to collapse frommechanical failure or fromchemical interaction of the formation with the drilling fluid. The Earth’s pressure gradient at sea level is 0.465 psi/ft,
which is equivalent to the height of a column of salt water with a density (1.07 SG) of 8.94 ppg.
In most drilling areas, the fresh water plus the solids incorporated into the water from drilling subsurface formations is sufficient to balance the formationpressures.

However, it is common to experience abnormallypressured formations that require high-density drilling fluids to control the formation pressures. Failure to control downhole pressures can result in aninflux of formation fluids, resulting inakick or blowout. Borehole stabilityis also maintained or enhanced by controlling the loss of filtrate to permeble formations and by careful control of the chemical composition of the drilling fluid. Most permeable formations have pore space openings too small to allow the passage of whole mud into the formation, but filtrate from the drilling fluid can enter the pore spaces. The rate at which the filtrate enters the formation depends on the pressure differential between the formation and the column of drilling fluid and the quality of the filter cake deposited on the formation face. 

Large volumes of drilling fluid filtrate and filtrates that are incompatible with the formation or formation fluids may destabilize the formation through hydration of shale and/or chemical interactions between components of the drilling fluid and the wellbore. Drilling fluids that produce low-quality or thick filter cakes may alsocause tight hole conditions, including stuck pipe, difficulty in running casing, and poor cement jobs

1.1.6 Assist in the Gathering of Subsurface Geological Data and Formation Evaluation

Interpretation of surface geological data gathered through drilled cuttings, cores, and electrical logs is used to determine the commercial value of the zones penetrated. Invasion of these zones by the drilling fluid, its filtrate (oil or water) may mask or interfere with interpretation of data retrieved or prevent full commercial recovery of hydrocarbon.

1.1.7 Other Functions
In addition to the functions previously listed, the drilling fluid should be environmentally acceptable to the area inwhich it is used. It should be noncorrosive to tubulars being used in the drilling and completion operations.
Most importantly, the drilling fluid should not damage the productive formations that are penetrated. The functions described here are a fewof themost obvious functions of a drilling fluid. Proper application of drilling fluids is the key to successfully drilling in various environments.


Ageneralized classification of drilling fluids can be based on theirfluid phase, alkalinity, dispersion, and type of chemicals used in the formulation and degrees of inhibition. In a broad sense, drilling fluids can be broken into five major categories.

1.2.1 Freshwater Muds—Dispersed Systems
The pHvalue of low-pHmudsmay range from7.0 to 9.5. Low-pHmuds include spud muds, bentonite-treated muds, natural muds, phosphate treated muds, organicthinned muds (e.g., red muds, lignite muds, lignosulfonatemuds), and organic colloid–treatedmuds. In this case, the lack of salinity of the water phase and the addition of chemical dispersants dictate the inclusion of these fluids inthis broad category.
1.2.2 Inhibited Muds—Dispersed Systems
These are water-base drilling muds that repress the hydration and dispersion of clays through the inclusion of inhibiting ions such as calcium and salt. There are essentially four types of inhibited muds: lime muds (high pH), gypsummuds (lowpH), seawatermuds (unsaturated saltwater muds, lowpH), and saturated saltwatermuds (lowpH).Newer-generation inhibited-dispersed fluids offer enhanced inhibitive performance and formation stabilization; these fluids include sodium silicate muds, formate brine-based fluids, and cationic polymer fluids.

1.2.3 Low Solids Muds—Nondispersed Systems
These muds contain less than 3–6% solids by volume, weight less than 9.5 lb/gal, and may be fresh or saltwater based. The typical low-solid systems are selective flocculent, minimum-solids muds, beneficiated clay muds, and low-solids polymer muds. Most low-solids drilling fluids are composed ofwaterwith varying quantities of bentonite and a polymer. The difference among low-solid systems lies in the various actions of different polymers.
1.2.4 Non aqueous Fluids
Invert Emulsions Invert emulsions are formed when one liquid isdis persed as small droplets in another liquidwith which the dispersed liquidis immiscible. Mutually immiscible fluids, such as water and oil, can be emulsified by shear and the addition of surfactants. The suspending liquid is called the continuous phase, and the droplets are called the dispersed or discontinuous phase. There are two types of emulsions used indrilling fluids: oil-in-water emulsions that have water as the continuous phase and oil as the dispersed phase and water-in-oil emulsions that have oil as the continuous phase andwater as the dispersed phase (i.e., invert emulsions) Oil-Base Muds (nonaqueous fluid [NAF]) Oil-base muds containoil (refined from crude such as diesel or synthetic-base oil) as the continuous phase and trace amounts of water as the dispersed phase. Oil-base muds generally contain less than 5% (by volume) water (which acts as a polar activator for organophilic clay), whereas invert emulsion fluids generally have more than 5% water in mud. Oil-base muds are usually a mixture of base oil, organophilic clay, and lignite or asphalt, and the filtrate is all oil.


To properly control the hole cleaning, suspension, and filtration properties of a drilling fluid, testing of the fluid properties is done on a daily basis. Most tests are conducted at the rigsite, and procedures are set forth
in the API RPB13B. Testing of water-based fluids and nonaqueous fluids can be similar, but variations of procedures occur due to the nature of the fluidbeing tested.
1.3.1 Water-Base Muds Testing
To accurately determine the physical properties of water-based drilling fluids, examination of the fluid is required in a field laboratory setting. In many cases, this consists of a fewsimple tests conducted by the derrickman or mud Engineer at the rigsite. The procedures for conducting all routine drilling fluid testing can be found in the American Petroleum Institute’s API RPB13B.

within ±0.1 lb/gal or ±0.5 lb/ftDensity Often referredto as themudweight,densitymay be expressedas pounds per gallon (lb/gal), pounds per cubic foot (lb/ft3), specific gravity (SG) or pressure gradient (psi/ft). Any instrument of sufficient accuracy 3 may be used. The mud balance is the instrument most commonly used. The weight of a mud cup attached to one end of the beam is balanced on the other end by a fixed counterweight
and a rider free to move along a graduated scale. The density of the fluid isadirect reading from the scales located on both sides of the mud balance.

Marsh Funnel Viscosity Mud viscosity is a measure of the mud’s resis- tance toflow.Theprimary function ofdrillingfluidviscosity is a to transport cuttings to the surface and suspend weighing materials. Viscosity must
be high enough that the weighting material will remain suspended but low enough to permit sand and cuttings to settle out and entrained gas to escape at the surface. Excessive viscosity can create high pump pressure, which magnifies the swab or surge effect during tripping operations. The control of equivalent circulating density (ECD) is always a prime concern when managing the viscosity of a drilling fluid. The Marsh funnel is a rig site instrument used tomeasure funnel viscosity. The funnel isdimensioned so that by following standard procedures, the outflow time of 1 qt (946ml) of freshwater at a temperature of 70±5◦F is26±0.5 seconds A graduated cup is used as a receiver.
Direct Indicating Viscometer This is a rotational type instrument powered by an electricmotor or by a hand crank .Mud is contained in the annular space between two cylinders. The outer cylinder or rotor sleeve is driven at a constant rotational velocity; its rotation in the mud produces a torque on the inner cylinder or bob. A torsion spring restrains the movement of the bob. A dial attached to the bob indicates its displacement on a direct reading scale. Instrument constraints have been adjusted

so that plasticviscosity, apparent viscosity, and yield point are obtained by using readings from rotor sleeve speeds of 300 and 600 rpm. Plasticviscosity (PV) in centipoise is equal to the 600 rpm dial reading minus the 300 rpm dial reading. Yield point (YP), in pounds per 100 ft 2, is equal to the 300-rpm dial reading minus the plasticviscosity. Apparent viscosity in centipoise is equal to the 600-rpm reading, divided by two.

Gel Strength Gel strength is a measure of the inter-particle forces and indicates the gelling thatwill occurwhen circulation is stopped. This property prevents the cuttings from setting in the hole. High pump pressure is generally required to “break” circulation inahigh-gel mud. Gel strength is measured inunits of lbf/100 ft 2.This reading is obtained by noting the maximum dial deflection when the rotational viscometer is turned at a low rotor speed (3 rpm) after the mud has remained static for some period of time (10 seconds, 10 minutes, or 30 minutes). If the mud is allowed to remain static in the viscometer for a period of 10 seconds, the maximum dial deflection obtainedwhen the viscometer is turned on is reported as the initial gel on the API mud report form. If the mud is allowed to remain static for 10minutes, themaximumdial deflection is reported as the 10-min gel. The same device is used to determine gel strength that is used to determine the plasticviscosity and yield point, the Variable Speed Rheometer/Viscometer. 

API Filtration Astandard API filter press is used to determine the filter cake building characteristics and filtration of a drilling fluid(Figure 1.4). TheAPI filter press consists of a cylindricalmud chambermade ofmaterials resistant to strongly alkaline solutions.Afilter paper is placed on the bottom of the chamber just above a suitable support. The total filtration area is 7.1 (±0.1) in. 2. Below the support is a drain tube for discharging the filtrate into a graduated cylinder. The entire assembly is supported by a stand so 100-psi pressure can be applied to the mud sample in the chamber.At the end of the 30-minute filtration time, the volume of filtrate is reported as API filtration. inmilliliters. To obtain correlative results, one thickness of the proper 9-cm filter paper—Whatman No. 50, S&S No. 5765, or the equivalent—must be used. Thickness of the filter cake is measured and reported in 32nd of an inch. The cake isvisually examined, and its consistency is reported using such notations as “hard,” “soft,” tough,” ’‘rubbery,” or “firm.”

Sand Content The sand content indrilling fluids is determined using a 200-mesh sand sieve screen 2 inches indiameter, a funnel to fit the screen, and a glass-sand graduated measuring tube (Figure 1.5). The measuring
tube is marked to indicate the volume of “mud to be added,” water to be added and to directly read the volume of sand on the bottom of the tube.Sand content of themud is reported in percent by volume.Also reported is thepoint of sampling (e.g.,flowline, shale shaker, suctionpit). Solids other than sandmay be retained on the screen (e.g., lost circulationmaterial), and the presence of such solids should be noted.

Liquids and Solids Content A mud retort is used to determine the liquids and solids content of a drilling fluid.Mud is placed in a steel container and heated at high temperature until the liquid components have been
distilled off and vaporized (Figure 1.6). The vapors are passed through a condenser and collected in a graduated cylinder. The volume of liquids (water and oil) is then measured. Solids, both suspended and dissolved, are determined by volume as a difference between the mud in container and the distillate in graduated cylinder. Drilling fluid retorts are generally designed to distill 10-, 20-, or 50-ml sample volumes


Geotextiles are the earliest type of multifunctional geosynthetic material. Their functions include reinforcement, separation, filtration, and drainage. When impregnated, they are used as containment. However, some newly developed products perform better than geotextiles in certain functions. For example, geogrids are developed specifically to tensile reinforce soil, while geonets are used to convey large-capacity flow. Although geotextile may also be made impermeable and used as containment by spraying bitumen or other polymers on it, geomembranes should be considered for a watertight containment system. The functions of geotextiles, geogrids, and geonets are described collectively in this section, where one material can be referred to the other.
Geotextile sheets are manufactured from fibers or yarns. Polymers are melted and forced through a spinneret to form fibers and yarns. They are subsequently hardened and stretched. The manufacturing process produces
woven or nonwoven geotextiles. In producing woven fabrics, conventional textile-weaving methodologies are used. For the nonwoven fabrics, the filaments are bonded together by thermal, chemical, or mechanical means (i.e., heating,using resin, or needle-punching).
Geogrids are mainly used as tensile reinforcement. Although biaxial geogrids are available, most geogrids are manufactured to function uniaxially. In manufacturing uniaxial geogrids, circular holes are punched on the polymer sheet, which is subsequently drawn to improve the mechanical properties. For biaxial geogrids, square holes are made on the polymer sheet, which is then drawn longitudinally and transversely. For some geogrids, the junctions between the longitudinal and transverse ribs are bonded by heating or knit-stitching.
Geogrid manufactured from yarns are typically coated with a polymer, latex, or bitumen. Geogrids have higher stiffness and strength than most geotextiles. 

The chapter now describes some major applications of geotextiles and related products

Reinforcement of Steep Slopes, Retaining Structures, and Embankments

Geotextiles and geogrids are used to tensile reinforce steep slopes, retaining structures, and embankments constructed over soft foundation (Fig. 1). Sheets of geotextile/geogrid are embedded horizontally in these soil structures. The shear stress developed in the soil mass is transferred to the geotextile sheets as tensile force through friction. The tensile strength of geotextile/geogrid and its frictional resistance with the soil are the primary items required for design.

The tensile strength of geosynthetic is obtained from the wide-width test. The ASTM standard specifies an aspect ratio (width-to-length) of 2 (i.e., 20 cm to10 cm). Soil confinement may increase the stiffness and strength of nonwoven spun-bonded needle-punched geotextile because of the interactions among the fibers, but it has negligible effect on the heat-bonded nonwoven geotextiles and woven geotextiles. Reduction factors (also known as partial factors of safety) are applied considering possible strength reduction of geotextiles by installation damage, creep, chemical and biological actions. Geotextiles may degrade by exposure to ultraviolet rays, high temperature, oxidation, and hydrolysis (when the environment is highly alkaline), but the effect is minimized when buried in soils.

The frictional behavior of a geotextile with site-specific soil must be determined by direct shear tests. Although the ASTM standard specifies a direct shear box with dimensions of 30 cm by 30 cm, the box with a plane area of 10 cm by 10 cm would be adequate for geotextiles. Pullout tests have been proposed in the last few decades for determining the anchorage capacity of geosynthetics; such tests are not relevant in determining the design parameters because they are subject to scale and boundary effects. For embankments and dikes constructed over a soft foundation that lacks bearing capacity and global stability, a layer or more of geotextile is laid at the base of the embankment. Vertical wick drains of geosynthetic composites or sand drains may be used to accelerate consolidation of the soft foundation. 

Geotextiles have also been used in conjunction with the underwater sand capping of contaminated submarine sediments. In these applications, the seam strength may dominate the design.

Both geotextiles and geogrids are used to reinforce steep slopes and retaining walls. For applications where large tensile stiffness and strength of reinforcement are required, geogrids should be used. A large shear box is
required to determine the frictional properties of the geogrid because the aperture size is large relative to the geotextile. Unlike geotextiles, where frictional behavior dominates the interaction with soil, the junction of some geogrids may provide interlocking. As geotextiles are very flexible, they are typically wrapped around the face of the slope or retaining wall and protected by vegetation, gunite, timber face, or concrete panels to prevent degradation by ultraviolet rays and vandalism.
Geogrids are increasingly used with modular blocks to provide an aesthetically pleasant wall appearance. As such, the connection between the blocks and geogrids plays an important role in design. The creep and stress relaxation behavior of geogrids are also studied in conjunction with wall design. In the design of reinforced slopes and walls, a limit equilibrium approach is used. The structure is checked for internal and external stabilities. In the internal stability analysis, a failure wedge is postulated and it is tied back into the stable soil zone. An adequate strength and length of reinforcement are secured. Theexternal stability is evaluated in a manner similar to conventional gravity/cantilever wall design. In the external stability analysis, possible modes of failure, such as direct sliding, overturning, and bearing capacity, are evaluated. The seismic design of reinforced slopes and retaining walls has also received wide attention in recent years.

Filter and Drainage Layer

Geotextiles are used to replace granular soil filters in the underdrain, as well as paved and unpaved roads. They are also used as chimney drain in an earth dam and behind retaining walls (Fig. 2). The hydraulic properties are a major consideration in design. The flow rate obtained from the tests is reduced using reduction factors considering soil clogging and blinding, creep reduction of void space, intrusion of adjacent materials into geotextile voids, chemical clogging, and biological clogging.
When functioning as a filter, the geotextile sheet is required to retain the soil while possessing adequate permeability to allow cross-plane flow to occur. The permittivity or permeability and apparent opening size or equivalent opening size of the geotextile are used in design. Permittivity is the coefficient of hydraulic conductivity normalized by the thickness of the geotextile. The filter is also expected to function without clogging throughout the lifetime of the system. The gradient ratio test and long-term flow tests may be used to investigate the clogging potential.


Figure 2 Geotextile as drainage layer or filter: (a) chimney drain in earth dam; (b) drain behind retaining wall; (c) underdrain; (d) drainage layer in tunnel.

If the geotextiles (usually nonwoven needle-punched geotextiles) are used as a drainage layer, the in-plane permeability is considered. Because the thickness decreases with increasing normal stress acting on it, the term “transmissivity” is used, where the coefficient of hydraulic conductivity is normalized by the geotextile thickness

Large-Capacity Flow with Geonets/Geocomposites

For drainage applications (such as landfills and surface impoundments), geonets and geocomposites are preferable to geotextiles. These are specifically manufactured to allow for large-capacity flow. Geonets have a parallel set of ribs overlying similar sets at various angles for drainage of fluids. Most geonets are manufactured from polyethylene. They are laminated with geotextiles on one or both surfaces to form drainage geocomposites (Fig. 3). Geonets are mostly manufactured from polyethylene; thus they have high resistance to leachate.

In geonets/geocomposites, the flow is no longer laminar, and thus Darcy’s law is invalid. The flow rate is used in lieu of transmissivity or coefficient of hydraulic conductivity to account for the turbulent flow. Because of the large normal stress acting on the plane of geonet/geocomposites, the crushing strength of the core has to be assessed. Geocomposites are sometimes tested with site-specific soils and liquid. A reduction in the flow rate is expected because of the intrusion of the geotextiles into the core. It is also important to ensure that geotextile sheets, if installed along the slope, do not delaminate from the geonets due to shear stress, because geocomposites are installed at a gradient to allow for gravity flow. The drainage systems of a geocomposite are usually constructed for allowance of cleaning by flushing because they are normally subject to biological

Figure 3 Geocomposite.

Separation and Reinforcement in Roadways

In the unpaved roads and railways, geotextile separates the subgrade and stonebase/ballast (Fig. 4). The California bearing ratio (CBR) of the soil subgrade may be used to determine if an unpaved road should be designed for separation or for separation and reinforcement. The intrusion of stone aggregates into the soil
subgrade is prevented by the geotextile in a roadway. In a railway, the fine soil particles are stopped from pumping into the stone aggregates. In addition to tensile strength, other mechanical properties of geotextiles, such as resistance to burst, tear, impact, and puncture, are used for designing geotextiles as a separator.

However, existing practice does not emphasize design when geotextiles are used as a separator compared to reinforcement and drainage applications. For unpaved roadways, the use of geotextile reinforcement results in cost savings because the thickness of stone aggregates may be reduced. In paved roads, the geotextiles may prevent reflective cracking. The geotextile or biaxial geogrids may be placed above the cracked old pavement followed by the asphalt overlays. The life of the overlay is prolonged in the presence of geosynthetic
materials, or a reduced thickness of overlay may be used while keeping the lifetime equivalent to the case without using the geotextile. In addition to preventing reflective cracking, the geosynthetic reinforces the asphalt pavement.
Figure 4 Geotextile as separator in unpaved roadway.

Coastal and Environmental Protection
Geotextiles are placed under erosion control structures, such as rock ripraps and precast concrete blocks (Fig. 5a). They are also used as silt fences at construction sites so that the soil particles are arrested from the runoff water. Geotextiles are also used as geocontainers on land or underwater as storage for slurry and for coastal protection. On land, the dredged materials or sands are pumped under pressure into sewn geotextile sheets. The geotextile inflates to form a tube (Fig. 5b). Geotextile tubes are extremely effective in dewatering the high-water-content slurry/sludge by acting as a filter. The geotextile tube may also be used as an alternative to dike and coastal protection. In such applications, the strength and filter characteristics of the geotextile are important design criteria.

Geocontainers are used for the disposal of potentially hazardous dredged materials and offer a more environmental-friendly means of disposing dredged materials offshore. The geotextile sheets are laid at the bottom of dump barges, filled with dredged sediments, and sewn. The containers are then transported to
the disposal site and dumped via a split hull barge.

Civil and Environmental Applications of Geosynthetics


Geosynthetics include exclusively manmade polymeric products such as geotextiles, geogrids, geonets, geomembranes, geosynthetic clay liners, and geocomposites. The term “geosynthetic” is used in favor of
geotextiles and geofabrics because 
  1. additional polymeric products are being developed and used with soils and 
  2.  the application is becoming more diversified.
Polypropylene, polyester, polyethylene, polyamide, polyvinyl choride, and polystyrene are the major polymers used to manufacture geosynthetics. It is not the properties of the polymers, but the properties of the final polymeric products that are of interest to civil and environmental engineering applications. Geosynthetics are used as part of the geotechnical, transportation, and environmental facilities. Geosynthetic products perform
five main functions: separation, reinforcement, filtration, drainage, and containment (hydraulic barrier). However, in most applications, geosynthetics typically perform more than one major function.


A. Testing Standards
Some basic standards used for geotextiles are adopted from the textile industries. However, geotechnical engineers realized the deficiencies and started to develop the standards relevant to their applications. The American Society for Testing and Materials (ASTM) is one developer of standardized testing procedures for
different geosynthetics. Most testing standards adopted or developed in other countries are outgrowths of ASTM standards. The Geosynthetic Research Institute (GRI) also provides testing standards to serve industrial needs, especially when related ASTM standards have not been developed. GRI standards are usually removed as related ASTM standards become available. ASTM standards, developed under Committee D35 for Geosynthetics, are listed in the Appendix. These standards were developed under several
subcommittees: terminology, mechanical properties, endurance properties, permeability and filtration, geosynthetic clay liners, geosynthetic erosion control, and geomembranes. New standards are constantly being developed. Details of test standards are published in ASTM (2000).
While ASTM standards are index tests, many civil engineering designs and applications require the geosynthetic materials to be tested with site-specific soils, with the testing conditions representing those in the field. These kinds of tests are known as performance tests.

B. Design by Function

Different organizations, agencies, and manufacturers provide design guidelines for geosynthetic applications. These design methods are determined by cost, specification (design by specification), or function (design by function). Public agencies have widely adopted the design-by-specification method. The minimum required value of the geosynthetic properties used in a particular application is specified. In the design-by-function method, the primary function of the geosynthetic material is identified. The available and required value of the particular property for that function is assessed to give a factor of safety (FS):

FS = allowable property from testing / required property for design

Designs require a factor of safety greater than unity to account for various uncertainties.

source : Marcel Dekker Inc (Reinforced  Soil Engineering)

Standard Test Procedures Manual - Stratigraphic Holes

Standard Test Prosedures Manual
Section :   SOILS

  1. Description of Test : This method covers the sampling of soils from stratigraphic holes. 


  1. A suitable drilling rig equipped with a 150 mm auger.
  2. Suitable bags and sampling containers such as tares to retain the natural moisture
  3. Munsel color chart.
  4. Pocket penetrometer


  1. Sampling :  Drill stratigraphic holes averaging 1.5 km intervals or less depending upon terrainevaluation,  along either hubline.  The depth of these holes will be pre-determined by the District Materials Engineer or designate, usually a 13.5 m depth is adequate. Record the hole number, station, offset from centerline as shown in Figure 104-1. Drill continuously until each sample depth is reached then pull the auger up rather than twist it to obtain a good sample.  Depths usually tested for moisture content are 0.3, 0.9,1.5m and then every 1.5 m until total depth is reached.Color coding and penetrometer readings may be taken when sampling for moisturecontent.  Moisture contents are required for topsoil and sand but no gravel.  Use STP 205-3 for moisture contents. Record the above information on Figure 104-1 together with any other pertinent remarks such as depth to water table, and depths at which rocks were encountered in the hole. Also include iron staining, odor from organic material, fossils, etc.The technician will inspect every 0.3 m of material to determine any soil changes.  If any change occurs, the depth will be recorded.  The Drill Operator can usually detect material changes by noting any changes in the rotational pressure gauge.
  2. Bagging and Labeling : lace a 3-5 kg sample of each soil type in a paper bag for further testing.  Control section, hole number, station, depth and type of material must be written on the bag and written on tag and placed in the bag. If granular material is encountered, take a 4000 g sample every 1.5 m in depth.

  1. Reporting Results : Complete as shown in Figure 104-1.


  1. Additional Testing : This information is required to determine if further testing should be completed.  All sample and any material changes should be clearly defined and well documented.
  2. Geological Soil Symbols : Symbols used for geological soil classification are as follows:
    TS  - Sutherland Till
    TB - Battleford Till
    TF - Floral Till
       u - Subscript to describe an unoxidized till eg: TFu
       o - Subscript to describe an oxidized till eg: TFo
      Sl - Silt
    CL  - Clay
    SD  - Sand
    GR - Gravel

FIGURE 104-1

source :

Standard Test Prosedures Manual - Fine and Coarse Aggregate Test Set

Standard Test Prosedures Manual
Section :   SAMPLING

  1. Description of Test : This method covers the sampling of coarse and fine aggregates for further testing as requiredaybolt viscosity is expressed in units of furol seconds at a specified temperature.

  1. Sampling pan. 
  2. Sample scoop. 
  3. Sample splitter and receptacles.  
  4. Sample bags or containers. 
  5. Sample identification tags. 
Number and Masses of Field Samples  

The required sample size is based on the type and number of tests to which the material is to be subjected. Amounts specified in Table No. 1 will provide adequate material for routine testing and quality analysis. For routine control, take one sample for every 2 hours of plant production. 


Samples will be reduced at the laboratory to testing size with the use of a sample splitter or by the quartering method. 

Shipping Samples
Transport aggregates in bags or containers that are constructed to prevent loss or contamination of any part of the sample, or damage to the contents from mishandling during shipment. Enclose complete identification with the sample to facilitate reporting of test results. 


  1. Sampling from the Conveyor Belt. Obtain at least three approximately equal increments selected at random from the unit or ot being sampled and combine to form a field sample whose mass equals or exceeds the minimum recommended in Table No. 1. Stop the conveyor belt while the sample increments are being obtained. Select a representative section in the middle of the belt.  Remove enough material from within the selected section such that the material contained will yield the required
    weight.  Carefully place all material into a container.    
  2. Sampling from a Flowing Aggregate Stream (Bins or Belt Discharge). Select samples by random method from the production. Sample from belt discharge only when plant is operating at normal capacity. Sample from bin discharge only when bins are nearly full in order to minimize change of obtaining segregated material. Obtain at least three approximately equal increments, at random and combine to form a field sample whose mass equals or exceeds the minimum recommended in Table No. 1. Take each increment from the entire cross section of the material as it is being discharged. For larger plants, a special sampling device may have to be constructed on site in order to accomplish the above requirement.  A rail or pivot system should be constructed to convey a sampling pan through the discharge stream at a uniform rate.  The pan must be large enough to intercept the entire flow and hold the required amount of sample without over flowing.
  3. Sampling In Place On Road (Bases and Subbases) . Select sample blocks or areas from completed construction work representing 500 t of production, or in accordance with respective contact specifications. Use a random method to select a representative sample from at least 3 sites within the area to be tested.  Combine all 3 samples to form a single field sample that can be reduced as required to the specified size in accordance with the respective contract specifications and test procedures. Clearly mark the specific areas from which the increment is removed.  A metal template placed over the area is a definite aid in securing approximately equal increment weights.Take all samples from the roadway for the full depth of the material, taking care to exclude any underlying material.
  4. Sampling From Windrow . Select sample blocks or areas from completed construction work representing 500 t of production, or in accordance with respective contract specification. Use a random method to select a representative sample from at least 3 sites within the areas to be tested.  Combine all 3 samples to form a single field sample that can be reduced as required to the specified size in accordance with the respective contract specifications and test procedures.

Aggregate samples may be taken for one of several reasons such as preliminary investigation of the source of supply, to control the product at the source of supply or to control operations at the site and to accept or reject material.

Sampling is equally as important as the testing and the sampler must use every precaution to obtain samples which will show the true nature and condition of the materials which they represent.  Sampling from the initial or final material discharge from a conveyor belt or a bin increases the chances of segregation and should be avoided.  The samples are to be taken while the plant is in full operation.

Samples for preliminary investigation testing are obtained by the party responsible for the development of the potential source (e.g. Gravel Investigation). Where practical, samples to be tested for quality should be obtained from the finished product.

source :

Standard Test Prosedures Manual - Marshal Stability and Flow - Asphalt Mixes

Standard Test Prosedures Manual


  1. Description of Test This method covers the measurement of resistance to plastic flow of cylindrical specimens of asphalt mixtures loaded on the lateral surface by means of the Marshall apparatus.  This method is for use with mixtures containing asphalt cement, asphalt cutback, and aggregate up to 25.4 mm maximum size. 
  2. Application of Test. The testing section of this method can also be used to obtain maximum load and flow for asphalt concrete specimens cored from pavements or prepared by STP 204-8, Preparation of Marshall Compaction Specimens.
  3. Units of Measure .Stability is measured in Newtons.  Flow is measured in mm

Equipment Required
  1. Breaking Head - the breaking head shall consist of upper and lower cylindrical segments or test heads having an inside radius of curvature of 50.8 mm accurately machined.  The lower segment shall be mounted on a base having two perpendicular guide rods or posts extending upward.  Guide sleeves in the upper segment shall be in such a position as to direct the two segments together without appreciable binding or lose motion on the guide rods.
  2. Loading Jack - the loading jack shall consist of a screw jack mounted in a testing frame and shall produce a uniform vertical movement of 50.8 mm/minute.  An electric motor may be attached to the jacking mechanism.
  3. Ring Dynamometer Assembly or Electronic Equivalent - one ring dynamometer of 2267 kg capacity and sensitivity of 4.536 kg up to 453.6 kg and 11.34 kg between 453.6 and 2267 kg shall be equipped with a micrometer dial.  The micrometer dial shall be graduated in 0.0025 mm.  Upper and lower ring dynamometer attachments are required for fastening the ring dynamometer to the testing frame and transmitting the load to the breaking head.
  4. Flowmeter - the flowmeter shall consist of a guide sleeve and a gauge.  The activating pin of the gauge shall slide inside the guide sleeve with a slight amount of frictional resistance.  The guide sleeve shall slide freely over the guide rod of the breaking head. The flowmeter gauge shall be adjusted to zero when placed in position on the breaking head when each individual test specimen is inserted between the breaking head segments.
  5. Water Bath - the water bath shall be at least 152 mm deep and shall be thermostatically controlled so as to maintain the bath at 60 ± 1o C.  The tank shall have a perforated false bottom or be equipped with a shelf for supporting specimens 51 mm above the bottom of the bath.
  6. Air Bath - the air bath for asphalt cutback mixtures shall be thermostatically controlled and shall maintain the air temperature at 25 ± 1o C
Materials Required
  1. Samples may include cored specimens, field or lab prepared specimens
Sample to be Tested
  1. Density of the specimen is required to obtain the volume for a correlation ratio.  Density can be determined as outlined in STP 204-21, DENSITY AND VOID CHARACTERISTICS.

Equipment Preparation
Thoroughly clean the guide rods and the inside surfaces of the test heads prior to making the test, and lubricate the guide rods so that the upper test head slides freely over them.

Sample Preparation
Samples will be prepared in accordance with STP 204-8, Preparation of Marshall Compaction Specimens or collected in accordance with STP 204-5, Asphalt Concrete Samples Obtained by Coring.

Test Procedure

Bring the specimens prepared with asphalt cement to the specified temperature by immersing in a water bath 30 minutes.  Maintain the bath or oven temperature at 60 ± 1o C for asphalt cement specimens.  Bring the specimens prepared with asphalt cutback to the specified temperature by placing them in the air bath for a minimum of 2 hours. Maintain the air bath temperature at 25 ± 1o C. The testing head temperature shall be maintained between 20 to 38o C.  Remove the specimen from the water bath, oven or air bath and place in the lower segment at the breaking head.  Place the upper segment of the breaking head on the specimen and place the complete assembly in position on the testing machine.  Place the flowmeter, where used, in position over one of the guide rods and adjust the flowmeter to zero while holding the sleeve firmly against the upper segment of the breaking head.  

Hold the flowmeter sleeve firmly against the upper segment of the breaking head while the test load is being applied.  Apply the load to the specimen by means of the constant rate of movement of the load jack or testing machine head of 50.8 mm/minute until the maximum load is reached and the load decreases as indicated by the dial.  Record the maximum load noted on the testing machine or converted from the maximum micrometer dial reading.  Release the flowmeter sleeve or note the micrometer dial reading, where used, the instant the maximum load begins to decrease.  Note and record the indicated flow value or equivalent units in mm if a micrometer dial is used to measure the flow. The elapsed time for the test from removal of the test specimen from the water bath to the maximum load determinations shall not exceed 30 seconds.


Collection of Test Results
For specimens other than 63.5 mm in thickness correct the load by using the proper multiplying factor from Table 1. The reports shall include the following information:
  1. Type of sample tested (lab sample or pavement core specimen).  For core specimens the height of each test specimen in mm shall be reported.
  2. Average maximum load in newtons, corrected when required.
  3. Average flow value in millimetres.
  4. Test temperature
TABLE 1 - Stability Correlation Ratios*
Volume of Specimen       Thickness of Specimen      Correlation Ratio
             (cm3)                                (mm)
200 to 213                                     25.4                         5.56
214 to 225                                     27.0                         5.00
225 to 237                                     28.6                         4.55
238 to 250                                     30.2                         4.17
251 to 264                                     31.8                         3.85
265 to 276                                     33.3                         3.57
277 to 289                                     34.9                         3.33
290 to 301                                     36.5                         3.03
302 to 316                                     38.1                         2.78
317 to 328                                     39.7                         2.50
329 to 340                                     41.3                         2.27
341 to 353                                     42.9                         2.08
354 to 367                                     44.4                         1.92
368 to 379                                     46.0                         1.79
380 to 392                                     47.6                         1.67
393 to 405                                     49.2                         1.56
406 to 420                                     50.8                         1.47
421 to 431                                     52.4                         1.39
432 to 443                                     54.0                         1.32
444 to 456                                     55.6                         1.25
457 to 470                                     57.2                         1.19
471 to 482                                     58.7                         1.14
483 to 495                                     60.3                         1.09
496 to 508                                     61.9                         1.04
509 to 522                                     63.5                         1.00
523 to 535                                     64.0                         0.96
536 to 546                                     65.1                         0.93
547 to 559                                     66.7                         0.89
560 to 573                                     68.3                         0.86
574 to 585                                     71.4                         0.83
586 to 598                                     73.0                         0.81
599 to 610                                     74.6                         0.78
611 to 625                                     76.2                         0.76

The measured stability of a specimen multiplied by the ratio for the thickness of the specimen equals the corrected stability for a 63.5 mm specimen.

Soil Testing Q & A

Soil testing... if you feel as though you have heard enough about soil sampling, you are in for a big surprise. With the increased focus on nutrient management planning of intensive livestock areas, and farm planning programs to manage fertilizer nutrients, we are on the verge of major soil sampling promotional campaigns in most provinces. For the average grower, fertilizer cost is also becoming a major challenge in budgetting for crop inputs. Soil testing is an excellent way to  minimize the ‘guesswork’ associated with seeding a crop for maximum  economic yield. This fertilization article reviews some of the common questions posed each year from crop advisers who take and interpret soil samples.

Collecting a good custom soil sample – why is it still a challenge? It has been said a thousand times,  soil sampling practices are where the vast majority of errors occur. If you  consider that the sample is subject to accepted North American handling protocols once it reaches the soil testing laboratory, any field sampling problem that affects the sample ahead of time will impact the results obtained and thus the recommendations made. For the sake of keeping a customer and  getting them used to the best science- based soil fertility planning tool, be sure you are getting good samples.

Why is it important to consult with, or take along, the farmer when custom soil sampling? The potential for sampling the ‘wrong’ location is very high in a field you have never been in before, trying to decide the best location to collect your soil cores. With the farmer riding along, or providing clear direction on paper ahead of time, the sample operator has clear guidance as to where not to sample in the field. This becomes critical,  considering the time and effort required to collect soil samples and the need for composite samples to be representative of the dominant production area in the field. Once these preferred sampling areas have been identified, marking them with GPS allows for future reference when sampling again.

Why do we insist that for a composite sample the operator collect 15 to 20 sample cores? When composite sampling, getting a representative sample is critical. While a composite sample will not provide any insight into the variability found in a particular field, picking the right  spots to represent the average production areas is critical. In collecting the sample, imagine what happens to the average value when one bad core (saline for instance) ends up mixed in with the rest. The more samples collected, the more dilution will occur from this one bad core.

For example, there are saline areas in many fields in semi-arid regions. However, when you get a soil sample back saying the field is saline, not just the three acres at the base of the hill you have always known about, you know that it is a poor representative sample for the field. One bad core mixed in with eight to 10 others is a far bigger problem than one bad core mixed in with 15 to 20 cores. If the differing areas of the field are large, they should be separated into a sub-region and a sample collected from that particular region. This will aid in fertilizer application rate management.  Sample number, or intensity in a field, should increase with the amount  of rainfall received, or where irrigation is used.

Sampling around last year’s fertilizer bands – how do you avoid high  residual nutrients? Selecting a sampling location to collect your soil cores also requires asking how fertilizer P and K were applied the year
before. While most N and S sources are mobile in the soil and move away from the band location in soil water, P and K additions will remain very close to their original band location. If applied in the seedrow, or in a side-band, these are areas to avoid sampling. Sometimes growers will apply P and K in the  mid-row band with their N and S, so these areas should also be avoided. A few simple questions can avoid excessively high soil nutrient levels which end up reducing confidence in the sample collected.

How does sampling to a uniform depth avoid disappointment? Nutrient concentration in the soil canvary significantly with soil depth. Care must be taken when collecting a  composite sample to ensure that the sampling depth is uniform, and if  different from the option provided on the sample bags, this is noted. For
example, if the laboratory suggests a sampling depth of zero to six inches and six to 24 inches, but you actually have samples that are zero to four inches and four to 16 inches, noting this on the sample bags will ensure that the laboratory uses the appropriate  conversion factors when estimating  the supply of available nutrients. A change in the depth you submit  to the laboratory is not a problem, it is just ensuring that you note on  the sample bag what depth the sample was collected.

Sample timing – Why is it important to sample at the same time each year?
One of the advantages that soil sampling provides is the opportunity to monitor soil nutrient changes and trends over time. However, to make a good comparison it requires sampling from the same areas from year to year, and sampling at the same time of year. Taking samples for spring seeded crops after fall harvest is ideal. Sampling in the fall prior to any tillage helps to  minimize field variability and ensures uniform sample core collection. Canola and pulse fields should be sampled later in the fall once soil temperatures drop below 50 degrees F (10 degrees C), while all cereal stubbles can be sampled after crop harvest. Where possible, avoid sampling frozen soils. Spring is also a good time to sample, with the laboratories offering rapid turn-aroundin sample handling.

Composite versus site-specific sampling, what are the advantages? One of the ways in which some farmers have changed their soil sampling  practices to minimize variability from year to year is to move to site-specific sampling. Using GPS, they establish a series of four or five co-ordinates in  their fields which they believe best  represent the field average. These are then provided to the sample operator, who drives to these locations using a truck-mounted GPS receiver. Once in these locations, the operator drives in a tight circle and collects four to five  samples for the composite of 15 to 20 total cores from the field. This  avoids sampling areas where problems are known to exist, such as salinity,  old yard sites and areas where manure was previously applied. With this site-specific information, the farmer can then make his own changes to application rates based on his past knowledge of crop response in specific areas of the field. 
Grid sampling – is it for your farm? Grid sampling has been proposed as a means of obtaining the most accurate picture of soil nutrient variability within fields. This variability can then be  managed with nutrient additions to increase field uniformity and uniformity in crop response. Grid sample cells vary in size, ranging from a low of one acre to a high of five acres. In many cases, grid sample results are used to manage less mobile nutrients like P and K. Areas low in P and K can receive more fertilizer, while those areas high in P and K will receive little or no fertilizer addition. From a cost of sampling perspective, grid sampling can be very expensive. While it is not conducted on an  annual basis, a five acre acre grid on a 160 acre field would require 32  separate analyses... cost prohibitive for many semi-arid cropping regions. While grid sampling has been shown to be  profitable in areas where building  soil P and K play a major role in increasing yield level and uniformity, it is not likely to be popular with  growers in areas where P and K are applied annually at rates similar  to crop removal.

*Dr. Adrian Johnston is Northern
Great Plains region director for
PPI/PPIC. Article reprinted with
permission of PPI/PPIC.
Reprinted in Canada from the November 2006 issue of Top Crop Manager (West) magazine with permission of Annex Publishing & Printing Inc

Selecting and Using a Soil Testing Laboratory

Taking a Soil Sample

Follow the specifc instructions provided by the soil testing lab you select.  The following guidelines will help ensure that a good sample is taken: Separate samples should be taken for distinct areas- front yard, back yard, vegetable garden, etc. The sample should represent  the soil in which the plants are or will be growing. Use a  spade or trowel to take 10-12 random samples across the area  of concern.  The samples are thin slices taken to a depth that  contains or will contain the bulk of the plant’s roots- 3 inches for turf; 6-8 inches for garden and landscape beds.  Mix together all of the slices in a clean bucket removing all rocks, debris, and
plant material.

Mailing in a Soil Sample

Don’t send wet soil; you should not be able to squeeze water  from the sample. Send a minimum of 1 cup and a maximum of  2 cups of soil per sample.  If no kit is provided, seal the soil in a  zip lock bag or use the special soil sample bag provided by the  Maryland Department of Agriculture and Maryland Cooperative  Extension.  Forms for most of the labs can be downloaded from  their websites. Be sure that all of your contact information is on  the form and mail it back to the lab with the sample, check for  the correct amount, and suffcient postage

Interpreting Test Results

Soil test reports from all of the labs will provide a graphical representation of results- the level of various nutrients from your soil (low medium, high, excessive).  “Optimal” and “excessive” levels mean that the nutrient concentration in the soil is more  than adequate for optimum plant growth.  Adding more of that  nutrient will not improve plant growth and may have undesirable  effects on the environment.

Be aware that the specifc turfgrass fertilizer recommendations  you receive will not be identical to Maryland’s.  This is due to  differences in soils, climate, and and state water quality policies.   Always follow University of Maryland recommendations for applying the right amount of nitrogen for healthy lawns.  Go  to the “Publications” section of our website to download  the following fact sheets: HG 103, “Fertilizing Facts for
Home Lawns”; FS 702, “Lawns and the Chesapeake Bay” (has more detailed information on grasscycling, slow release  nitrogen fertilizers, and fertilizing responsibly); and HG 42,  “Soil Amendments and Fertilizers” (contains broad fertilizer guidelines for many garden and landscape plants).

Abbreviations and Terms Found in Soil Test

The labs listed in the chart provide defnitions and explanations  of soil sampling terms and concepts.  The list below will help you  better understand the soil test reports you receive. pH-  soil pH is a measure of a soil’s hydrogen ion concentration.  The greater the number of hydrogen ions the more acidic the soil.  The pH scale is 1-14. 

Soils with pH levels below 7.0 are considered acidic and soils with pH levels above 7.0 are  considered alkaline. Soil pH is a critical measurement for gardeners because it affects the availability of nutrients for uptake by plant roots.  Most garden and landscape plants grow best in soils with a pH of 5.5–7.0.  Certain plant nutrients can become  unavailable or excessively available outside this range, leading  to plant growth problems. But there are exceptions:  for example,  plants in the azalea and blueberry family grow best at pH 4.0-5.0.

Macronutrients: these are required in the greatest quantity by plants. Sulfur (S) is rarely tested because soils in Maryland are rarely defcient.  Nitrogen (N) is not usually tested because it is constantly changing.
P-  phosphorous
K-  potassium
Mg-  magnesium
Ca-  calcium

Micronutrients:  These important nutrients are required in  relatively small quantities.  Defciencies are rarely a problem in  Maryland soils, especially in the Central and Western regions.   Eastern Shore gardeners may want to be sure that boron is  included in the test they select.
Fe-  iron
Zn-  zinc
Cu-  copper
Mn-  manganese
B-  boron

Heavy metals:  excessive levels are a concern, especially in soils where food crops are grown and children play.  These elements can be a health hazard when 1)tracked into the house via shoes and tools, 2)ingested by young children, or 3)ingested from food crops grown in contaminated soil.  For more information on lead,
refer to Maryland Cooperative Extension fact sheet HG #18, ”Lead in Garden Soil.”
Pb-  lead
Ni-  nickel
Cd-  cadmium
Cr-  chromium

OM-  organic matter; includes living and decomposed plant and animal tissues (dead leaves, soil fungi, plant roots, etc.  Soil organic matter drives a soil’s biological and chemical processes.  OM test results are given on a weight basis. Usually a sample is weighed in the lab and then ignited to burn off the carbon compounds, leaving only the mineral soil.  The sample is reweighed to determine the OM%.   Gardeners who add lots of  organic matter to their soils may be surprised that the OM content is less than 5%.  This is because OM is lighter than mineral soil  and the measurement is based on weight, not volume. CEC-  cation exchange capacity measures the capacity of a soil  to hold and release nutrient ions.  Soils high in clay and organic
matter will have high CEC.  This measurement will vary across Maryland soils.  Adding organic matter is recommended where the CEC is less than 10.


Plants need a relatively large amount of nitrogen for healthy growth.  Plant roots take up nitrogen in the
nitrate and ammonium forms.  Unlike most other nturients, nitrogen does not come from mineral soil.  Instead it comes “naturally” from organic matter, lightning and legumes (plants that convert nitrogen in air to nitrate nitrogen.)

Fertilizing Responsibly for a Healthy Chesapeake Bay

Nitrogen and phosphorous are the two key nutrient pollutants of  waterways in Maryland that contribute to the complex problem  known as eutrophication. These nutrients encourage blooms of  algae that cloud the water and block sunlight causing underwater grasses to die. This has negative affects on aquatic life and  birds. Huge numbers of microorganisms in the water then use up oxygen as they feed on and break down the algae once it has died. Dissolved oxygen in the water quickly declines, depriving fsh, crabs and other aquatic life forms of needed oxygen.It is estimated that up to 80% of the nitrogen entering groundwater and surface water comes from non-point sourcesfarms, public lands, and private landscapes.  About one-half of excessive or mis-applied nitrogen fertilizer enters surface water fairly quickly as run-off from hard surfaces, lawns and gardens.  The other half travels for at least 10 years through soil and underground water before it eventually enters the Chesapeake  Bay (for Marylanders who live east of the Eastern Continental
Divide, located in Garrett County).

So mistakes in measuring and applying fertilizers today can contribute to nutrient pollution  problems many years in the future.Farmers, municipalities, corporations, AND homeowners all  have a duty to reduce the fow of nitrogen and phosphorous into streams, rivers, and the Chesapeake Bay.    Marylanders with lawns should be careful to drastically reduce or eliminate phosphorous fertilization if their soil test results show phosphorous (phosphate) levels that are “adequate”, “optimum”, or “excessive”.  The following companies  offer lawn fertilizers that contain no phosphorous or a low percentage (3%-5%) of phosphorous: Lebanon-Seaboard (Greenview), Espoma, LESCO, Scotts.

10 Ways to Achieve a Healthy Home Landscape Without Harming the Chesapeake Bay

  1. Take a soil test every 3 to 4 years. Fertilize according tosoil test recommendations. Use less than the recommended amounts listed on fertilizer packages.
  2. Leave grass clippings on your lawn (grasscycling.) They are a source of nitrogen for your lawn and will not contribute to thatch build-up in fescue or bluegrass lawns.
  3. Home gardeners tend to over-fertilize fower and vegetable gardens.  Reduce or eliminate fertilizer applications in wellestablished beds if organic matter is being added each year.  
  4. Don’t fertilize trees and shrubs if they appear healthy  and are making adequate shoot and leaf growth.Compost plant residues or incorporate them directly into soil.  
  5. Discard plants with serious disease problems.
  6. When appropriate, substitute slow-release fertilizers for those that are highly soluble and substitute locally available organic fertilizers (well-decomposed farmyard manure, backyard compost and municipal leaf compost) for manufactured chemical fertilizers.
  7. Keep fertilizers off hard surfaces.  Rain water will carry fertilizer salts into storm drains and surface waters and contribute to nutrient pollution of our waterways. 
  8. Over time, rainfall causes bare soil to erode and become compacted. Keep bare soil covered with a mulch and plant ground covers in areas where turf won’t grow.  Plant winter cover crops in vegetable gardens - like oats, winter rye and crimson clover.  
  9. Avoid excessive foot or equipment traffc to prevent soil compaction, especially when the soil is wet.  Construct terraces for beds on sloped ground. Keep soil in raised beds framed with solid sides. 
  10. To melt winter ice, use calcium magnesium acetate (CMA), potassium chloride (KCl), sodium chloride (NaCl) or calcium chloride (CaCl2).  Do not use urea, potassium nitrate, or other chemical fertilizers containing nitrogen or phosphorous.  The salts in these fertilizers may burn the foliage and roots of adjacent plants and wash into and pollute waterways.
Feed The Soil First!
The surest way to improve soil quality and  plant growth is  the  regular  incorporation  of  organic matter  such  as composted  yard waste. Organic matter  improves  soil structure, slowly  releases nutrients,  increases benefcial microbial  activity,  and  reduces  the  need  for  purchased fertilizers

Authors : Jon Traunfeld, Regional Specialist, Home and Garden
Information Center, Maryland Cooperative Extension
Reviewers: Patricia Steinhilber, Ph.D., Nutrient Management
Coordinator, Maryland Cooperative Extension and Judy
McGowan, Nutrient Management Specialist, Maryland
Department of Agricultur