DREL/2010 SPECTROPHOTOMETER Soil and Irrigation Water Portable Laboratory Manual

Transcription

1 DREL/2010 SPECTROPHOTOMETER Soil and Irrigation Water Portable Laboratory Manual Hach Company, Printed in U.S.A. All rights reserved. js/cth ED

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3 TABLE OF CONTENTS PREFACE... vii SECTION 1 INTRODUCTION Soil and Irrigation Water Manuals Using This Manual Extracting Soil Samples Soil Extraction Guide Using the Apparatus in the Kit Accurately Measuring Liquids Using Eye Droppers and Graduated Cylinders Using the Soil Scoops Alternative Procedure... 4 SECTION 2 SAMPLE COLLECTION AND PREPARATION Soil Preparation Sampling, Drying, Grinding and Screening Soil Sampling Filtering Soil Extracts Using Additional Apparatus Example of Procedure Using Alternative Apparatus Determining the Dilution Factor Conversion from ppm to lbs/acre or kg/ha Extraction Guide Obtaining Water Samples SECTION 3 SOIL EXTRACTION PROCEDURES AQUEOUS EXTRACTION, Used for Salinity and ph BRAY P1 (WEAK) EXTRACTION, Used for Phosphorus in Acid Soils BRAY P2 (STRONG) EXTRACTION, Used for Phosphorus in Acid Soils CALCIUM PHOSPHATE SOIL EXTRACTION, Used for Sulfate CALCIUM SULFATE SOIL EXTRACTION, Used for Nitrate SATURATED CALCIUM SULFATE EXTRACTION, Used for Gypsum Requirement and Exchangeable Sodium MEHLICH 1 EXTRACTION, Used for Calcium and Magnesium, Phosphorus, Potassium and Sodium MEHLICH 2 EXTRACTION, Used for Calcium and Magnesium, Phosphorus, Potassium and Sodium NEUTRAL NORMAL AMMONIUM ACETATE EXTRACTION, Used for Calcium and Magnesium, Potassium and Sodium iii

4 TABLE OF CONTENTS, continued OLSEN SODIUM BICARBONATE EXTRACTION, Used for Phosphorus and Potassium POTASSIUM CHLORIDE EXTRACTION, Used for Total Exchangeable Acidity SATURATED SOIL PASTE, Used for ph and Soluble Salts SMP BUFFER EXTRACTION, Used for Lime Requirement SECTION 4 SOIL ANALYSIS PROCEDURES SOIL ANALYSIS PROCEDURES, 4.1 Calculation of Cation Exchange Capacity and Percent Base Saturation for Soil CALCIUM, Using EDTA with a Digital Titrator CALCIUM + MAGNESIUM, Using EDTA with a Digital Titrator CALCIUM + MAGNESIUM, Calcium and Magnesium; Calmagite Colorimetric Method GYPSUM REQUIREMENT, EDTA Titration Method Using Digital Titrator LIME ESTIMATION, FREE (EXCESS), Effervescence Method NITRATE, HR, Cadmium Reduction Method ORGANIC MATTER, Dichromate Method ph, Hach One Combination ph Electrode Method with an EC10 Portable Meter PHOSPHORUS, REACTIVE, PhosVer 3 (Ascorbic Acid) Method POTASSIUM, Tetraphenylborate Method SALINITY(CONDUCTIVITY), Pocket Pal Conductivity Tester SOLUBLE SALTS (SALINITY), Saturated Paste Method with Pocket Pal Conductivity Tester SULFATE, SulfaVer 4 Method SULFUR REQUIREMENT, Titrimetric Sulfuric Acid Method SECTION 5 SOIL TEXTURE ESTIMATION TOTAL EXCHANGEABLE ACIDITY, NaOH with a Digital Titrator SECTION 6 IRRIGATION WATER PROCEDURES ALKALINITY, Phenolphthalein and Total Using Sulfuric Acid with a Digital Titrator CHLORIDE, Using Silver Nitrate with a Digital Titrator CONDUCTIVITY, Using Pocket Pal Conductivity Tester iv

5 TABLE OF CONTENTS, continued HARDNESS, TOTAL, Using EDTA with a Digital Titrator NITRATE, HR, Cadmium Reduction Method ph, Hach One Combination ph Electode Method with a EC10 Portable Meter Sample ph Measurement Two-Standard Calibration in Automatic Mode with Temperature Probe PHOSPHORUS, REACTIVE, (Also called Orthophosphate) PhosVer 3 (Ascorbic Acid) Method SULFATE, SulfaVer 4 Method SECTION 7 SODIUM ESTIMATION AND SODIUM ADSORPTION RATIO CALCULATIONS Na meq/l for Irrigation Water Procedure Sample Calculations GENERAL INFORMATION HOW TO ORDER v

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7 PREFACE This portable laboratory provides basic analyses for soil fertility assessment and irrigation water quality when routine laboratory analysis is not convenient or economical. This includes remote areas where facilities are not available or in a classroom where an instructor wants to present the basics of soil analysis. Prepackaged chemicals, simplified equipment and easy-to-follow procedures make Hach methods easy and quick to use. The DREL/2010 Soil and Irrigation Water Portable Laboratory was designed to meet the needs of professional scientists and non-scientists alike. Every possible effort was made to insure the results will be meaningful and applicable. The data obtained should lead the analyst to interpretations that correlate with interpretations from a competent full service soil laboratory. The procedures in this manual were modified from the following books and publications. 1. Handbook on Reference Methods For Soil Testing, Revised Edition The Council On Soil Testing and Plant Analysis 1111 Plant Science Building Athens, Georgia 2. Recommended Chemical Soil Test Procedures for the North Central Region Bulletin No. 499 (Revised) North Central Regional Publication No. 221 (Revised) North Dakota Agricultural Experiment Station North Dakota State University Fargo, North Dakota Diagnosis and Improvement of Saline and Alkali Soils Agricultural Handbook No. 60 United Stated Department of Agriculture Issued February 1954 (Out of Print) Compiled by the United States Salinity Laboratory Staff 4. Methods of Soil Analysis, Part 2 American Society of Agronomy Madison, Wisconsin Soil Testing and Plant Analysis, Third Edition Soil Science Society of America, Inc. Madison, Wisconsin Water Analysis Handbook, Second Edition Hach Company Loveland, Colorado vii

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9 SECTION 1 INTRODUCTION 1.1 Soil and Irrigation Water Manuals The two manuals supplied with this kit acquaint users with Hach procedures and techniques necessary for soil and irrigation water characterization. The DREL/2010 Soil and Irrigation Water Procedures Manual contains directions for performing the analyses. The Hach Soil and Irrigation Water Interpretation Manual helps interpret the results by providing basic information on soil fertility, soil characterization, plant nutrition, fertilizer recommendation, and irrigation water quality. This manual also contains a section on common conversion factors used in soil and water analysis, a glossary of terms, reorder information, and technical support information Using This Manual This manual is arranged in sequential sections: Section 1: aquaints the reader with some of the equipment and analytical techniques used with the apparatus. Section 2: details sampling and sample preparation for analysis. Section 3: contains soil extraction procedures (see information below). Section 4: contains soil analysis procedures in alphabetical order. Section 5: details soil texture estimation. Section 6: contains irrigation water analysis procedures Extracting Soil Samples To analyze for a specific substance(s) in a soil, you often need to extract that substance fromthe soil with a solvent (extractant). The analysis is then completed on the solution containing the substance. This manual contains all current Hach soil extraction procedures. The following Extraction Guide outlines which extractions are used when analyzing for the specific substances or parameters listed below each extraction. It is important to use the indicated extraction. More than one type of extraction for a given sample may be necessary. The DREL/2010 portable laboratory does not include all Hach extractants. Instead, a core system is provided with the capability to customize the system, depending on the extraction procedures used. 1

10 INTRODUCTION, continued The Mehlich 2 extract is included because: 1. Mehlich 2 is a viable choice for phosphorus extraction from most types of soils. 2. Other macronutrients (i.e., potassium, calcium, and magnesium) are extracted with Mehlich 2, allowing for their measurement and subsequent determination of cation exchange capacity and percent base saturation in neutral to acidic soils Soil Extraction Guide Determining the correct soil extract to use is based on the following criteria: 1. The geographical region of the soil. 2. The extracts used and recommended by local soil experts (usually government agencies or universities). In the United States, local landgrant universities perform this function. 3. The physical and chemical properties of the soil. The following matrix describes the extracts supplied by Hach and the parameters for which the extracts are used. Extractant Aqueous* Calcium Sulfate* Bray 1 Bray 2 Calcium Phosphate* Calcium Sulfate, saturated* Mehlich 1 Mehlich 2* Neutral normal Ammonium Acetate Olsen Potassium Chloride* Saturated Soil Paste SMP Buffer* Parameter(s) Analyzed on Extract Salinity, ph Nitrate Phosphorus (acid soils) Phosphorus (acid soils) Sulfate Gypsum requirement, exchangeable sodium Calcium + Magnesium, phosphorus, potassium Calcium + Magnesium, phosphorus, potassium Calcium + Magnesium, sodium, potassium Phosphorus, Potassium Total exchangeable acidity ph, soluble salts Lime requirement * Indicates these supplies for the extraction are included in the DREL/2010 Soil and Irrigation Water Portable Laboratory 2

11 INTRODUCTION, continued Two methods for determining lime requirement are included in this manual. The SMP buffer method is used for soils with lime requirements above 2 tons/acre. However, when soils have a lime requirement below 2 tons/acre or in tropical soils with high reserves of aluminum, determining total exchangeable acidity should be considered. For screening purposes, soil salinity is determined with this kit using a 1:1 soil suspension instead of a saturated paste extract. However, where salinity management and leaching requirements are of prime importance, salinity should be determined using the traditional saturated paste method. Hach Company provides a Soil Saturation Extract Kit (Cat. No ) to use with the Pocket Pal TDS Tester. 1.2 Using the Apparatus in the Kit Accurately Measuring Liquids Using Eye Droppers and Graduated Cylinders When small sample quantities are used, the accuracy of measurements is important. Figure 1 illustrates the proper technique for reading the sample level or the meniscus formed when the liquid wets the cylinder or wall of the dropper. Figure 1 Reading the Meniscus Using the Soil Scoops A set of soil scoops is included with the kit for sample measurement. The set consists of three different sized scoops: 0.85 cc (1 g), 1.70 cc (2 g), and 4.25 cc (5 g). In addition, a 0.2-g spoon is included for use in the procedures. Use the following procedure when using the scoops: 1. Use a spatula to stir the soil sample. 3

12 INTRODUCTION, continued 2. Dip the scoop into the center of the soil sample to obtain a heaping scoop full. 3. Hold the scoop firmly and tap the handle of the scoop sharply three times with a spatula to settle the soil. 4. Hold the blade of the spatula perpendicular to the top of the scoop and strike off the excess soil. 5. Empty the soil into the appropriate container for a given procedure Alternative Procedure Use a balance instead of scoops to weigh the sample. Hach offers two balances for soil testing. The AccuLab PocketPro 150 B is a top-loading balance with readability of 0.1 g. For higher accuracy, a pan balance (Ohaus) with readability to 0.01 g also is available. 4

13 SECTION 2 SAMPLE COLLECTION AND PREPARATION 2.1 Soil Preparation Sampling, Drying, Grinding and Screening The following method is commonly used to prepare soil samples for subsequent testing. It applies to all classes of soils. The procedure is based on the Recommended Chemical Soil Test Procedures for the North Central Region, Bulletin No. 499 (Revised), October, 1980 published by The North Dakota Agricultural Experiment Station, North Dakota State University Soil Sampling For meaningful results, it is of utmost importance that the soil sample be representative of the area being tested. Depending on the size of the sampling area, take 15 to 20 subsamples from the area being sampled and mix them together in a clean container. Use a sample of this mixture during analysis to represent the area being tested. Subsamples (which should be approximately the same size) may be obtained with a coring tube, soil auger or shovel. Avoid sampling very unusual areas such as old manure piles, lime piles, fence lines, etc. REMEMBER: The test results can no better represent the testing area than does the soil sample from that area. The most valid information regarding sampling can be obtained from the local extension office, university or government agricultural department. Sample preparation consists of drying, crushing, mixing and sieving. These steps assure that a correct, representative sample is analyzed. Dry the sample as outlined below. 1. Break up the large chunks of soil and spread it out to air dry. Avoid contamination by fertilizer dusts or other such sources of contamination. If a forced-draft oven or similar drying device is used, set the heat no higher than 60 C (140 F). 2. Use a short board or similar device to crush the air dried soil. Note: A soil crusher may be used in the laboratory (Cat. No ) to grind and screen the soil. Note: A mortar and pestle (included in the DREL/2010) may also be used. Take care to avoid grinding rocks. 3. Pass the crushed soil through the 10-mesh (2 mm) soil sieve assembly included with the kit. 4. Store the soil in a cool, dry place until the analysis is complete. Rinse the spatula with demineralized water before stirring each sample. Note: Store the sample, because it may be necessary to re-test. 5

14 SAMPLE COLLECTION AND PREPARATION, continued Filtering Soil Extracts Prepare a filter for filtration as follows: 1. Fold a sheet of filter paper by creasing it in half and then in half again. Separate one edge from the other three to form a cone. Place the folded paper in the funnel. See Figure 2. Figure 2 Folding the Filter Paper 2. Open the filter in a manner that forms an inverted cone. Check the filter paper for holes or tears they can make the results inaccurate. 3. Rinse the funnel with demineralized water. Shake the funnel to remove excess water. 4. Place the filter paper in the funnel. 5. Place the funnel into a round sample bottle or plastic cup to collect the extract. Prefolded filter paper, sized for the filtration apparatus listed below, is available in packs of 500 (Cat. No ) Using Additional Apparatus Multiple Filtration Assembly A filtration apparatus (Cat. No ) is available for filtering soil extracts. The apparatus includes a ten-place funnel stand, funnels and a cup holder to receive the filtrate. See Figure 3. 6

15 SAMPLE COLLECTION AND PREPARATION, continued Figure 3 Multiple Filtration Assembly Soil Shaker A soil shaker (Cat No ) is a convenient way to extract large numbers of samples and perform extended shaking times. The shaker has two speeds. The low speed shakes at about 180 reciprocations per minute, ideal for soil extraction. The shaker has a timer and may be used with disposable plastic cups (Cat. No ) and lids (Cat. No ). Additional shaking trays (Cat. No ) and cup racks (Cat. No ) are available. See Figure 4. Figure 4 Soil Shaker Digital Dispensers Wheaton Variable Volume Digital Dispensers are available in 3 sizes: ml (Cat. No ) ml (Cat. No ) 5-59 ml (Cat. No ) 7

16 SAMPLE COLLECTION AND PREPARATION, continued These dispensers are accurate and convenient for dispensing precise volumes of extracts or dilution water. They come with variable neck adaptors to fit a wide variety of containers. Procedures for set-up, use, and maintenance are provided with the dispenser. Pour-out Dispensers Hach fixed volume dispensers pour out volumes of 5.0 and 10 ml and are convenient to use for extracting solutions. They are less expensive than the variable volume dispensers, but less adaptable for laboratory use. Soil Grinder The Dynacrush Soil Crusher (Cat. No ) significantly speeds soil preparation by crushing and sieving air-dried soil samples in less than 1 minute. See Figure 5. Figure 5 Soil Grinder Pour-Thru Cell Hach provides a Pour-Thru Cell for the DR/2010 Spectrophotometer (Cat. No ). The cell replaces the matched sample cells and provides constant optical characteristics for improved test precision; it also decreases the time spent when multiple samples are analyzed. See Figure 6. 8

17 SAMPLE COLLECTION AND PREPARATION, continued Figure 6 Pour-Thru Cell Disposable Cups and Lids These cups (Cat. No ) and lids (Cat. No ) reduce the time spent cleaning labware. Most soil procedures in this manual can be adapted to their use. The shaking apparatus and filtration assembly have been designed to use them. ADDITIONAL APPARATUS LIST Description Unit Cat. No. AccuLab Pocket Pro 150 B Balance...each Ohaus Pan Balance...each Soil Crusher 120/240V...each Soil Shaker 115V...each Soil Shaker 230V...each Digital Dispenser, ml...each Digital Dispenser, ml...each Digital Dispenser, 5-59 ml...each Pour-out Dispenser, 5 ml...each Pour-out Dispenser, 10 ml...each Pour-Thru Cell, DR/ each Filtration Apparatus Assembly...each Filter Paper, prefolded, for /pkg Disposable Cups, 150 ml /pkg Disposable Lids, for cups /pkg

18 SAMPLE COLLECTION AND PREPARATION, continued Example of Procedure Using Alternative Apparatus The following example for analyzing phosphorus uses the alternative apparatus mentioned above and a different soil extractant than offered with the DREL/2010 Spectrophotometer. In this example, the following changes were made: Different extract Different soil:extract ratio Use of Soil Grinder Use of Multiple Filtration Apparatus Use of Digital Dispensers Use of Pour-Through Cell Choose Extractant SOIL PREPARATION 1. Grind and sieve the samples with a mechanical grinder. SOIL EXTRACTION 1. Choose appropriate extractant (e.g., Bray 1). 2. Use disposable cups instead of plastic vials (especially for large numbers of samples). 3. Use a digital dispenser instead of a graduated cylinder. 4. Use soil scoops to measure soil (e.g. 2 grams) into cup. 5. Set dispenser to desired volume (20 ml of extract per cup). Add extract to the cup containing the soil sample. 6. Cover cups and shake for 5 minutes. 7. Filter extracts using Filtration Assembly 10

19 SAMPLE COLLECTION AND PREPARATION, continued Determination of Phosphorus 3:00 minutes 1. Add 1 ml of filtered extract to clean cup, then add 24 ml demineralized water (25 ml total). Swirl to mix. 2. Add one PhosVer 3 Powder Pillow and mix well. Swirl to dissolve the powder. 3. Wait 3 minutes for color development. 4. Rinse Pour-Thru Cell with demineralized water, then zero the instrument. 5. Pour reacted samples into Pour-Thru Cell. 6. Multiply readings by the dilution factor to obtain ppm P in soil. 2.2 Determining the Dilution Factor Use this formula to determine actual ppm in soil: ppm soil basis = Instrument reading Vol. extractant (ml) Final analysis vol. (ml) Sample weight (g) Aliquot vol. of extract (ml) In the above procedure, the following numbers would be used in the equation. Apparent Value = 0.46 ppm Volume extractant = 20 ml Final analysis volume = 25 ml Sample weight = 2 g Aliquot volume of extract = 1 ml ml 25 ml 115 ppm in soil = g 1 ml 11

20 SAMPLE COLLECTION AND PREPARATION, continued 2.3 Conversion from ppm to lbs/acre or kg/ha The following formula assumes a sample bulk density of 1.2 g/cm 3 and uses a 0.3 constant to reflect the assumption For the example above, assume the soil was sampled to a depth of 6 inches (15.24 cm). So: in. = 207 lbs/acre phosphorus To convert from ppm to kg/ha, the formula is: kg/ha = ppm soil basis cm of sample depth For the above sample with a cm sample depth, the conversion is: cm = 235 kg/ha 2.4 Extraction Guide This guide is a quick reference to Hach s soil analysis products. It will aid the analyst in customizing the DREL/2010 Portable Laboratory or building a soil testing laboratory. The program numbers listed assume the DR/2010 Spectrophotometer is used. If the same soil:extractant ratio and sample dilution is used, the multiplier will be the same for all Hach spectrophotometer instruments. Any Hach colorimeter or spectrophotometric may be used with the appropriate water calibration curve.. lbs/acre = ppm soil basis 0.3 inches of sample depth Table 1 Spectrophometric Methods Using Water Calibration Curves Parameter Extraction Ratio Dilution Program Multiplier Unit Nitrate Calcium Sulfate 1:2 direct ppm soil basis Organic Matter Potassium Dichromate 1:10 direct % soil basis Phosphorus Bray 1 1:10 1: ppm soil basis Phosphorus Bray 2 1:10 1: ppm soil basis Phosphorus Mehlich 1 1:5 1: ppm soil basis Phosphorus Mehlich 2 SIW* 1:10 1: ppm soil basis Phosphorus Olsen 1:20 3: ppm soil basis Phosphorus Mehlich 2 1:8.5 1: ppm soil basis Potassium Ammonium Acetate 1:5 3:25 user entered ppm soil basis Potassium Mehlich 1 1:5 3:25 user entered ppm soil basis Potassium Mehlich 2 1:8.5 3:25 user entered 70.8 ppm soil basis Potassium Mehlich 2 SIW* 1:10 3:25 user entered 83.3 ppm soil basis Potassium Olsen 1:20 3:25 user entered 167 ppm soil basis Ca + Mg Ammonium Acetate 1:5 0.2: , ppm soil basis Ca + Mg Mehlich 1 1:5 0.2: , ppm soil basis Ca + Mg Mehlich 2 1: : , ppm soil basis Ca + Mg Mehlich 2 SIW* 1:10 0.2: , ppm soil basis Sulfur (sulfate) Calcium Phosphate 1:2 direct ppm soil basis *The Mehlich 2 SIW uses a different extraction ratio for easy application in the field. 12

21 SAMPLE COLLECTION AND PREPARATION, continued Table 2 Ion Selective Electrode Parameter Extraction Ratio Dilution Program Multiplier Unit Lime Rqmt. Lime Rqmt. Pillow 8:21 direct 1 Tons/acre 2.5 Obtaining Water Samples Table 3 Titrimetric Methods Parameter Extraction Ratio Dilution Cartridge Multiplier Unit Ca + Mg Ammonium Acetate 1:5 1 ml 0.08 M EDTA digits 10 meq/100 g Ca + Mg Mehlich 1 1:5 1 ml 0.08 M EDTA digits 10 meq/100 g Ca + Mg Mehlich 2 1:8.5 1 ml 0.08 M EDTA digits meq/100 g 5.88 Ca + Mg Mehlich 2 SIW 1:10 2 ml 0.08 M EDTA digits 5 meq/100 g Sodium Calcium Sulfate 1:20 1 ml 0.8 M EDTA Calculated from Gypsum Rqmt. meq/100 g Sulfur Rqmt. Water 10 g sample 8.0 N H 2 SO 4 digits x 64 meq/100 g Gypsum Rqmt. Calcium Sulfate 1:20 1 ml 0.8 M EDTA Tons/acre Total Exchangeable Acidity Potassium chloride 5 g 50 ml 1.6 N NaOH digits 25 meq/100 g The minimum volume of water recommended for analysis is approximately 1 liter. Take care to obtain a representative sample. Satisfactory samples of some waters can be obtained only by mixing several portions collected at different times. Collection and mixing technique depend on local conditions. Samples from wells should be collected after the pump has run for 10 minutes. Samples from streams should be taken from running water. The most valid information regarding sampling can be obtained from the local extension office In general, the shorter the elapsed time between collection and analysis of a sample, the more reliable the analytical data will be. Changes resulting from chemical and biological activity may alter the composition of the sample. 13

22 SAMPLE COLLECTION AND PREPARATION, continued Use the following procedure to obtain a water sample: 1. Rinse the sample container 3 times with the water to be analyzed. 2. Fill the container completely full with the water to be analyzed and cap tightly. 3. Analyze the sample as soon as possible. 14

23 SECTION 3 SOIL EXTRACTION PROCEDURES 15

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25 AQUEOUS EXTRACTION (1:1 or 1:2) Used for Salinity and ph Method For Soil Extraction 1. Dry the soil sample. Screen it to a fineness of 0-2 mm with the Hach Soil Sieve. Note: Careful preparation is important to assure volumetric measurement of the sample. See the introductory sections for soil sampling and sample preparation. 2. Using a 5-gram scoop, measure 4 scoops of prepared soil into a 120-mL snap-top container. Note: Steps 2 and 3 make a 1:1 water/soil suspension. To make a 1:2 suspension, add 40 ml (instead of 20 ml) of demineralized water to a 120-mL snap-top container. Note: A balance may be used to weigh 20 g of soil. 3. Using a 25-mL graduated cylinder, accurately measure 20 ml of demineralized water into the 120-mL snap-top container. Note: To prevent confusion when working with several samples, label each snap-top container with the sample or test name. 4. Shake the contents of the container for 1 minute at 10-minute intervals for a 30-minute period. Note: Rinse the spatula with demineralized water before stirring each sample. Note: The Soil Shaker ( or ) and plastic cups can be used for multiple samples. Shaking time is 30 minutes. 30:00 minutes 5. After 30 minutes, use the prepared sample for salinity and ph determination. Note: Because conductivity is affected by minute amounts of potassium chloride resulting from ph determination, measure the salinity of the sample before measuring the ph. 17

26 AQUEOUS EXTRACTION, continued Summary of Method Use the Aqueous Extraction method to prepare soil for salinity and ph measurements. This method applies to all classes of soil. Filtering the soil suspension is not necessary to determine ph or salinity; measurements are made directly in the suspension. REQUIRED REAGENTS AND APPARATUS Quantity Required Description Per Test Unit Cat. No. Cylinder, graduated, 25 ml each Soil Sieve each Scoop, 5-gram each Spatula, stainless steel each Snap-top Container, 120 ml each OPTIONAL APPARATUS Balance, AccuLab Pocket Pro 150B... each Weighing Paper /pkg For technical support and ordering information, see General Information section. In the U.S.A. call to place an order. Outside the U.S.A. Contact the Hach office or distributor serving you. 18

27 BRAY P1 (WEAK) EXTRACTION Used for Phosphorus in Acid Soils Method For Soil Extraction Preparing the Bray P1 Extractant Bray P1 1. Measure 20 ml of the Bray P1 Soil Extractant Concentrate into a 25-mL graduated cylinder. 2. Transfer the extractant concentrate to one of the 200-mL fliptop dispensing bottles provided. 3. Add demineralized water to the dispensing bottle until the volume reaches the bottom of the neck. Invert several times to mix. Note: Do not use undiluted concentrate; it must be diluted 1:10 before use. 4. Label the bottle with the extractant name and date prepared to avoid confusion when working with several extractants. Extracting the Soil 1. Dry the soil sample. Screen it to a fineness of 0-2 mm with the Hach Soil Sieve. Note: Careful preparation is important to assure volumetric measurement of the sample. See the introductory sections for soil sampling and sample preparation. 2. With a 2-g (1.70 cc) soil scoop, add one scoop of soil to a 120-mL snaptop container. Note: A balance may be used to weigh 2.0 g of soil Using a 25-mL graduated cylinder, accurately measure 20 ml of the prepared Bray P1 Soil Extractant into the container. 4. Close the lid and shake the contents of the container for 5 minutes Note: The Soil Shaker ( or ) and plastic cups can be used for multiple samples.

28 BRAY P1 (WEAK) EXTRACTION, continued 5. Using a plastic funnel and filter paper, filter the extracted sample into another 120-mL snap-top container. Save the filtered liquid (filtrate) for analysis. Limit filtration time to 10-minutes. The filtrate is stable for about 12 hours. Note: The Filtration Assembly can be used for multiple samples. Sampling and Storage The diluted Bray P1 extract solution is stable for about 12 months. Protect the extractant from evaporation and contamination. Summary of Method The Bray P1 Soil Extractant is widely used for extracting phosphorus from acid soil. Hydrogen ions (H + ) in the extractant make phosphorus more soluble. The method also uses fluoride (F - ) to lower the activity of aluminum (Al 3+ ), calcium (Ca 2+ ) and iron (Fe 3+ ) in the extraction system. Clay soils with a moderately high degree of base saturation decrease the ability of the extract to dissolve phosphorus. Normally, this method should be limited to soils with a ph of less than 6.8 when the texture is silty clay or finer. With calcareous soils or at higher ph levels, fine-textured soils may be tested, but they require higher ratios of extractant to soil. This method is also suited for organic soils. Bray P1 values are often used in association with Bray P2 values to determine readily-available phosphorus vs. reservoir (labile) phosphorus. Bray P2 is a stronger acid and usually gives a higher phosphorus result because it extracts the reservoir phosphorus. As the Bray P2:Bray P1 ratio approaches 1, the 20

29 BRAY P1 (WEAK) EXTRACTION, continued phosphorus reservoir is being depleted and the amount of phosphorus added can be effectively managed. The procedure is based on the Handbook on Reference Methods for Soil Testing, 1980 edition, published by the Council for Soil Testing and Plant Analysis. REQUIRED REAGENTS Quantity Required Description Per Test Unit Cat. No. Bray P1 Soil Extractant Concentrate ml/10 tests...1 L REQUIRED APPARATUS Bottle, poly, 200 ml each Cap, 3-piece, w/ screen each Cylinder, graduated, poly, 25 ml each Filter Paper, circular, 15 mm /pkg Funnel, poly, 82 mm each Snap-top Container, 120 ml each Soil Scoop, 2 g each Soil Sieve each OPTIONAL APPARATUS Balance, AccuLab Pocket Pro 150B...each Disposable Cups /pkg Disposable Lids, for cups /pkg Filtration Assembly w/ 10 funnels, cup rack and funnel rack...each Filter Paper, for Filtration Assembly, pre-folded...500/pkg Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 115V...each Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 230V...each Weighing Paper...500/pkg For technical support and ordering information, see General Information section. In the U.S.A. call to place an order. Outside the U.S.A. Contact the Hach office or distributor serving you. 21

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31 BRAY P2 (STRONG) EXTRACTION Used for Phosphorus in Acid Soils Preparing the Bray P2 Extractant Method For Soil Extraction Bray P2 1. Measure 20 ml of the Bray P2 Soil Extractant Concentrate into a 25-mL graduated cylinder. 2. Transfer the extractant concentrate to one of the 200-mL fliptop dispensing bottles provided. 3. Add demineralized water to the dispensing bottle until the volume reaches the bottom of the neck. Invert several times to mix. 4. Label the bottle with the extractant name and date prepared to avoid confusion when working with several extractants. Note: Do not use undiluted concentrate; it must be diluted 1:10 before use. Extracting the Soil 1. Dry the soil sample. Screen it to a fineness of 0-2 mm with the Hach Soil Sieve. Note: Careful preparation is important to assure volumetric measurement of the sample. See the introductory sections for soil sampling and sample preparation. 2. With a 2-g (1.70 cc) soil scoop, add one scoop of soil to a 120-mL snaptop container. Note: A balance may be used to weigh 2.0 g of soil. 3. Using a 25-mL graduated cylinder, accurately measure 20 ml of the prepared Bray P2 Soil Extractant into the container. 4. Close the lid and shake the contents of the container for 5 minutes Note: The Soil Shaker ( or ) and plastic cups can be used for multiple samples. 23

32 BRAY P2 (STRONG) EXTRACTION, continued 5. Using a plastic funnel and filter paper, filter the extracted sample into another 120-mL snap-top container. Save the filtered liquid (filtrate) for analysis. Limit filtration time to 10 minutes. The filtrate is stable for about 12 hours. Note: The Filtration Assembly can be used for multiple samples. Sampling and Storage The diluted Bray P2 extract solution is stable for about 12 months. Protect the extractant from evaporation and contamination. Summary of Method The Bray P2 Soil Extractant is widely used for extracting phosphorus from acid soil. Hydrogen ions (H + ) in the extractant make phosphorus more soluble. The method also uses fluoride (F - ) to lower the activity of aluminum (Al 3+ ), calcium (Ca 2+ ) and iron (Fe 3+ ) in the extraction system. Clay soils with a moderately high degree of base saturation decrease the ability of the extract to dissolve phosphorus. Normally, this method should be limited to soils with a ph of less than 6.8 when the texture is silty clay or finer. With calcareous soils or at higher ph levels, fine-textured soils may be tested, but they require higher ratios of extractant to soil. This method is also suited for organic soils. Bray P2 values are often used in association with Bray P1 values to determine readily available phosphorus vs. reservoir (labile) phosphorus. Bray P2 is a stronger acid and usually gives a higher phosphorus result because it extracts the reservoir phosphorus. As the Bray P2:Bray P1 ratio 24

33 BRAY P2 (STRONG) EXTRACTION, continued approaches 1, the phosphorus reservoir is being depleted and the amount of phosphorus added can be effectively managed. The procedure is based on the Handbook on Reference Methods for Soil Testing, 1980 edition, published by the Council for Soil Testing and Plant Analysis. REQUIRED REAGENTS Quantity Required Description Per Test Unit Cat. No. Bray P2 Soil Extractant Concentrate ml/10 tests...1 L REQUIRED APPARATUS Bottle, poly, 200 ml each Cap, 3-piece, w/ screen each Cylinder, graduated, poly, 25 ml each Filter Paper, circular, 15 mm /pkg Funnel, poly, 82 mm each Snap-top Container, 120 ml each Soil Scoop, 2 g each Soil Sieve each OPTIONAL APPARATUS Balance, AccuLab Pocket Pro 150B...each Disposable Cups /pkg Disposable Lids, for cups /pkg Filtration Assembly w/ 10 funnels, cup rack and funnel rack...each Filter Paper, for Filtration Assembly, pre-folded...500/pkg Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 115V...each Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 230V...each Weighing Paper...500/pkg For technical support and ordering information, see General Information section. In the U.S.A. call to place an order. Outside the U.S.A. Contact the Hach office or distributor serving you. 25

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35 CALCIUM PHOSPHATE SOIL EXTRACTION Used for Sulfate Method For Soil Extraction 1. Dry the soil sample. Screen it to a fineness of 0-2 mm with the Hach Soil Sieve. Note: Careful preparation is important to assure volumetric measurement of the sample. See the introductory sections for soil sampling and sample preparation. 2. Using a 5-g scoop (4.25 cc), measure 5 scoops of prepared soil into a 120-mL snap-top container. Note: A balance may be used to weigh 25grams of soil. 3. Add 50 ml of demineralized water to the container. 4. Add the contents of one Sulfate Extractant 1 Powder Pillow. Close the lid. 5. Shake the container for 10 minutes. Note: The Soil Shaker ( or ) and plastic cups can be used for multiple samples. 6. Add one level 3.5-cc scoop of activated Charcoal Powder to the container. Close the lid and shake to mix. 7. Using a plastic funnel and filter paper, filter the extracted sample into another 120-mL snap-top container. Save the filtered liquid (filtrate) for analysis. The filtrate is stable for about 4 hours. Note: The Filtration Assembly can be used for multiple samples. 27

36 CALCIUM PHOSPHATE SOIL EXTRACTION, continued Summary of Method Soluble sulfate, plus a fraction of the adsorbed sulfate, is extracted with a solution of calcium phosphate (CaHPO 4 ) provided by the extractant. The phosphate ions displace the adsorbed sulfate, and the calcium ions inhibit the extraction of organic matter, eliminating contamination from the extractable organic sulfur. Activated charcoal is mixed with the extraction solution before filtering to form a colorless, clear extract. REQUIRED REAGENTS Quantity Required Description Per Test Unit Cat. No. Sulfate Extractant Powder Pillows /pkg Activated Charcoal Powder cc g REQUIRED APPARATUS Cylinder, graduated, mixing, 50 ml each Filter Paper, circular, 15 mm /pkg Funnel, poly, 82 mm each Snap-top Container, 120 ml each Scoopula, stainless steel each Soil Scoop, 3.5 cc each Soil Scoop, 5 g each Soil Sieve each OPTIONAL APPARATUS Balance, AccuLab Pocket Pro 150B... each Disposable Cups /pkg Disposable Lids, for cups /pkg Filtration Assembly w/ 10 funnels, cup rack and funnel rack... each Filter Paper, for Filtration Assembly, pre-folded /pkg Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 115V... each Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 115V... each Weighing Paper /pkg For technical support and ordering information, see General Information section. In the U.S.A. call to place an order. Outside the U.S.A. Contact the Hach office or distributor serving you. 28

37 CALCIUM SULFATE SOIL EXTRACTION Used for Nitrate Method For Soil Extraction 1. Dry the soil sample. Screen it to a fineness of 0-2 mm with the Hach Soil Sieve. Note: Careful preparation is important to assure volumetric measurement of the sample. See the introductory sections for soil sampling and sample preparation. 2. Using a 5-g scoop (4.25 cc), measure 6 scoops of prepared soil into a 120-mL snap-top container. Note: A balance may be used to weigh 30 grams of soil. 3. Using a 0.2-gram plastic spoon, add 2 level spoonfuls of the calcium sulfate powder to the container. Note: A balance may be used to weigh 0.4 of calcium sulfate. 4. Using a 50-mL graduated cylinder, accurately measure 60 ml of demineralized water and transfer it to the snap-top container. 5. Close the lid and shake the container vigorously for 1 minute. Note: The Soil Shaker ( or ) and plastic cups can be used for multiple samples. 6. Using a plastic funnel and filter paper, filter the extracted sample into another 120-mL snap-top vial. Save the filtered liquid (filtrate) for analysis. The filtrate is stable for about 2 hours. Note: The Filtration Assembly may be used for multiple samples. 29

38 CALCIUM SULFATE SOIL EXTRACTION, continued Summary of Method The Calcium Sulfate Extraction is essentially an aqueous extraction; the calcium sulfate aids in the filtration step. It is widely used for extracting nitrate-nitrogen from soils and can be used for all classes of soil. The procedure is based on the Recommended Chemical Soil Test Procedures for the North Central Region, Bulletin No. 499 (revised), October 1980, published by the North Dakota Agricultural Experiment Station, North Dakota State University. REQUIRED REAGENTS Quantity Required Description Per Test Unit Cat. No. Calcium Sulfate Powder g g REQUIRED APPARATUS Cylinder, graduated, mixing, 50 ml each Filter Paper, circular, 15 mm /pkg Funnel, poly, 82 mm each Measuring Spoon, 0.2 g each Snap-top Container, 120 ml each Soil Scoop, 5 g each Soil Sieve each OPTIONAL APPARATUS Balance, AccuLab Pocket Pro 150B... each Disposable Cups /pkg Disposable Lids, for cups /pkg Filtration Assembly w/ 10 funnels, cup rack and funnel rack... each Filter Paper, for Filtration Assembly, pre-folded /pkg Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 115V... each Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 230V... each Weighing Paper /pkg For technical support and ordering information, see General Information section. In the U.S.A. call to place an order. Outside the U.S.A. Contact the Hach office or distributor serving you. 30

39 Method SATURATED CALCIUM SULFATE EXTRACTION For Soil Extraction Used for Gypsum Requirement and Exchangeable Sodium Preparing the Extractant 1. Using the 1-gram soil scoop, add one level scoop of calcium sulfate to a fliptop dispensing bottle. 2. Add demineralized water until the volume reaches the bottom of the neck. 3. Shake the dispensing bottle vigorously several times over a 30-minute period to dissolve the calcium sulfate (a small amount may not dissolve). Note: Lable the bottle with the extractant name when working with other extractants. Extracting the Soil 1:00 minute 1. Dry the soil sample. Screen it to a fineness of 0-2 mm with the Hach Soil Sieve. Note: Careful preparation is important to assure volumetric measurement of the sample. See the introductory sections for soil sampling and sample preparation. 2. Using the 5-gram soil scoop, add one scoop of the soil into a 120-mL snap-top container. Note: A balance may be used to weigh 5 grams of soil. 3. Using a 25-mL graduated cylinder, accurately measure 100 ml of the saturated sulfate solution and transfer it to the snap-top container. 4. Close the lid. Shake the container for 1 minute at 10-minute intervals over a 30-minute period. Note: The Soil Shaker ( or ) and plastic cups can be used for multiple samples. 31

40 SATURATED CALCIUM SULFATE EXTRACTION, continued 5. Using a plastic funnel and filter paper, filter the extracted sample into another 120-mL snap-top container. Use the filtered extract to determine gypsum requirement and exchangeable sodium. Note: The Filtration Assembly can be used for multiple samples. Summary of Method This method is used to determine gypsum requirement and, by calculation, can estimate the meq/100 g of exchangeable sodium in the sample. The procedure is based on the principle that the calcium ions in the saturated solution of calcium sulfate will replace the exchangeable sodium in the soil. The number of milliequivalents of sodium displaced equals the number of Ca 2+ milliequivalents extracted from the saturated calcium sulfate solution. 32

41 SATURATED CALCIUM SULFATE EXTRACTION, continued REQUIRED REAGENTS Quantity Required Description Per Test Unit Cat. No. Calcium Sulfate Power... 1g/10 test...20 g REQUIRED APPARATUS Cylinder, graduated,25 ml, poly each Filter Paper, circular, 15 mm /pkg Funnel, poly, 82 mm each Measuring Spoon, 0.2 g each Snap-top Container, 120 ml each Scoopula, stainless steel each Soil Scoop, 1g each Soil Sieve each OPTIONAL APPARATUS Balance, AccuLab Pocket Pro 150B... each Disposable Cups /pkg Disposable Lids, for cups /pkg Filtration Assembly w/ 10 funnels, cup rack and funnel rack...each Filter Paper, for Filtration Assembly, pre-folded...500/pkg Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 115V...each Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 230V...each Weighing Paper...500/pkg For technical support and ordering information, see General Information section. In the U.S.A. call to place an order. Outside the U.S.A. Contact the Hach office or distributor serving you. 33

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43 MEHLICH 1 EXTRACTION Used for Calcium and Magnesium, Phosphorus, Potassium and Sodium Preparing the Mehlich 1 Extractant Method For Soil Extraction MEHLICH 1 1. Measure 20 ml of the Mehlich 1 Soil Extractant Concentrate into a 25-mL graduated cylinder. 2. Transfer the extractant concentrate to one of the flip-top dispensing bottles provided. 3. Add demineralized water to the dispensing bottle until the volume reaches the bottom of the neck. Invert several times to mix. 4. Label the bottle with the extractant name to avoid confusion when working with other extractants. The Mehlich 1 Soil Extractant is now ready for use. Preparing the Soil 5:00 minutes 1. Dry the soil sample. Screen it to a fineness of 0-2 mm with the Hach Soil Sieve. Note: Careful preparation is important to assure volumetric measurement of the sample. See the introductory sections for soil sampling and sample preparation. 2. Using a 5-g scoop, measure one scoop of prepared soil into a 120-mL snap-top container. Note: A balance may be used to weigh 5 grams of soil. 3. Using a 25-mL graduated cylinder, accurately measure 25 ml of the diluted Mehlich 1 Soil Extractant into the cylinder, then transfer it to the snap-top container. 4. Close the lid. Shake the container for 5 minutes. Note: The Soil Shaker ( or ) and plastic cups can be used for multiple samples. 35

44 MEHLICH 1 EXTRACTION, continued 5. Using a plastic funnel and filter paper, filter the extracted sample into another 120-mL snap-top container. Note: The Filtration Assembly can be used for multiple samples. 6. Use this filtered extract for calcium and magnesium, phosphorus and potassium analysis. Note: The filtered Mehlich 1 soil extract is stable for approximately 24 hours. Sampling and Storage The filtered Mehlich 1 soil extract is stable for approximately 24 hours. If stored longer, refrigerate to prevent microbial growth. Summary of Method Also called the Double Acid Extraction, this method is used primarily to determine phosphorus, potassium, calcium, magnesium and sodium in soils with exchange capacities of less than 10 meq/100 g, are acid in reaction (ph 6.5), and are relatively low in organic matter content (5%). This method is not suited for alkaline soils. The method is well suited for potassium determination using an ion selective electrode. The procedure is based on the Handbook on Reference Methods for Soil Testing, 1980 edition, published by The Council on Soil Testing and Plant Analysis. 36

45 MEHLICH 1 EXTRACTION, continued REQUIRED REAGENTS Quantity Required Description Per Test Unit Cat. No. Soil Extraction Concentrate, Mehlich ml/8 test...1 L REQUIRED APPARATUS Bottle, polyethylene, 200 ml each Cap, 3-piece, w/screen each Cylinder, graduated, polymethylpentene, 25mL each Filter Paper, circular, 15 mm /pkg Funnel, poly, 82 mm each Snap-top Container, 120 ml each Soil Scoop, 5 g each Soil Sieve each OPTIONAL APPARATUS Balance, AccuLab Pocket Pro 150B... each Disposable Cups /pkg Disposable Lids, for cups /pkg Filtration Assembly w/ 10 funnels, cup rack and funnel rack...each Filter Paper, for Filtration Assembly, pre-folded...500/pkg Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 115V...each Shaker Assembly, includes 4 sample racks, 2-speed shaker, time switch, and shaker plate, 230V...each Weighing Paper...500/pkg For technical support and ordering information, see General Information section. In the U.S.A. call to place an order. Outside the U.S.A. Contact the Hach office or distributor serving you. 37

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47 MEHLICH 2 EXTRACTION Used for Calcium and Magnesium, Phosphorus, Potassium and Sodium Preparing the Mehlich 2 Extractant Method For Soil Extraction MEHLICH 2 1. Measure 20 ml of the Mehlich 2 Soil Extractant Concentrate into a 25-mL graduated cylinder. Preparing the Soil 2. Transfer the extractant concentrate to one of the flip-top dispensing bottles provided. 3. Add demineralized water to the dispensing bottle until the volume reaches the bottom of the neck. Invert several times to mix. 4. Label the bottle with the extractant name to avoid confusion when working with other extractants. The Mehlich 2 Soil Extractant is now ready for use. 5:00 minutes 1. Dry the soil sample. Screen it to a fineness of 0-2 mm with the Hach Soil Sieve. Note: Careful preparation is important to assure volumetric measurement of the sample. See the introductory sections for soil sampling and sample preparation. 2. Using a 2-g scoop, measure one scoop of prepared soil into a 120-mL snap-top container. Note: A balance may be used to weigh 2 g of soil. 3. Using a 25-mL graduated cylinder, accurately measure 25 ml of the diluted Mehlich 2 Soil Extractant into the cylinder, then transfer it to the snap-top container. This solution is referred to as Mehlich 2 SIW. Note: Most Mehich 2 extractants are prepared using 17-mL of concentratate. The DREL/2010 Portable Laboratory uses 20-mL for ease of use in the field. 4. Close the lid. Shake the container for 5 minutes. Note: The Soil Shaker ( or ) and plastic cups can be used for multiple samples. 39