by: Dr. Bob Lippert and Dr. Kathy Moore Which section of the lab would you like to visit?

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1 by: Dr. Bob Lippert and Dr. Kathy Moore Which section of the lab would you like to visit? Web Pages of Specific Southeastern Soil Testing Labs Return to Dr. Bob Lippert s FAQ Web Site Soil receiving and preparation n

Sample Receiving - The soil samples are organized in a set of 100 and are logged in with lab numbers in the order they are received.

unique lab number so it is easier to keep track of them within th lab.

The blank is space left in the group where there will be no soil but only the chemicals which are added for extraction.

2 Sample Receiving - The soil samples are organized in a set of 100 and are logged in with lab numbers in the order they are received. Even though the samples have numbers and letters given to them by the farmer or ho gardener, the lab assigns each sample with a unique lab number so it is easier to keep track of them within th lab. Preparing the Samples for Analysis - A "blank" and two "check" samples are placed in each set for quality control. The blank is space left in the group where there will be no soil but only the chemicals which are added for extraction. At the end of the process, when the plant nutrients are analyzed, all the nutrients in the blank "sample" should read zero. The two check samples (in this case checks "D" and "F") are soils with a known nutrient content.

3 When they are analyzed, they should give nutrient levels within a certain numerical range. Notice the range of colors of soil from the same state. Also, many labs analyze 5 soil samples supplied quarterly through NAPT (North American Proficiency Testing Program). The labs send their results back to NAPT and receive a summary report from NAPT including results from all the participating labs. The labs can then compare their results with many other labs across the nation. Drying Racks - The samples are dried at room temperature with a fan or at a low temperature (if they are very wet) on drying racks. The low temperature is used to eliminate possible volatilization of the essential elements.

4 Grinding the Samples - With one pass through a "grinder" each sample is broken up and sieved through a 1 mesh screen.

5 Before and After Grinding - The grinding and sieving process breaks up the soil and removes rocks and other debris. This is important since one soil sample may represent up to 20 acres of a farmer s field.

6 Checking the Forms - The order of the samples is double checked against the sample submission forms in each set. The forms are then taken to the data processor who enters the name and address information along with the lab numbers into the database. After the samples are analyzed, the data is electronically merged with the other information from the forms to generate the final soil test report. STANDARD MINERALS Standard Mineral Analysis What is a soil extractant? A soil test utilizes an extractant to determine the amount of plant nutrients in the soil. A soil extractant is a solution made up of water and a certain concentration of chemicals which is thoroughly mixed with the soil and then filtered for analysis. The Mehlich-1 extractant

7 works very well as a soil extractant but some states in the Southeast have switched to the Mehlich-3 extractant. These states have significant acerages of calcareous soils with ph values greater than 7.0. For these soils, the Mehlich-3 extractant performs much better than the Mehlich-1 extractant. The Mehlich-1 extractant is used by the Southeastern state supported labs in Alabama, Florida, Tennessee, Virginia, Georgia and South Carolina as well as some private labs. The Mehlich-1 extractant (implemented in 1953) was developed by Dr. Adolph Mehlich for the North Carolina Department of Agriculture Soil Testing Division. It is a versatile soil extractant that is used for determining the amounts of phosphorus, potassium, calcium, magnesium, zinc, manganese, copper and boron. It is made up of a dilute solution of hydrochloric and sulfuric acids, thus it is often referred to as the "double acid" extractant. It works well for acidic, low cation exchange capacity (CEC) soils which encompasses essentially all of the soils in the Southeast. The Mehlich-3 extractant is used by the Southeastern state supported labs in Kentucky and North Carolina as well as some private labs. In an attempt to make a universal extractant that could be used for any soil in the world, Dr. Mehlich developed the Mehlich-2 extractant which was used for about 2 years. The Mehlich-2 contained 4 different chemicals but the chloride in the extractant was causing laboratory instrument problems. Subsequently, Dr. Mehlich developed the Mehlich-3 extractant by changing the chemical composition of the Mehlich-2 extractant slightly to exclude the chloride component. In addition, he added a chelating agent to increase the amount of micronutrients extracted, particularly copper. The Mehlich-3 extractant was adopted in 1984 and is being used throughout the world. Scooping Samples - The samples are transferred into sample extraction containers using a 4 ml volumetric scoop and leveled with a Teflon bar for consistent volume. This volume represents approximately 5 grams of soil.

8 Extracting the Plant Nutrients - Twenty milliliters (ml) of the Mehlich 1 extraction solution is added to each sample. The extractant is a weak solution of hydrochloric acid and sulfuric acid (0.05 N HCl N H 2 SO 4 ) and when mixed with soil, will displace and dissolve the plant nutrients which are held on to the soil particles.

9 Shaking - The containers are shaken for 5 minutes to give the extracting solution good contact with the soil and to allow it time to remove the plant nutrients from the soil. More about how the extracting solution works.

10 Filtering - The soil and solution mixture is filtered through filter paper. The soil is trapped in the filter paper and the extracting solution with the now dissolved nutrients is collected in the tubes.

11 Transferring to Test Tubes - The extractant and dissolved nutrients that pass through the filter paper is transferred into test tubes which fit into the auto-analyzer tray of the ICP.

12 Inductively Coupled Plasma (ICP) - The solution is pumped through tubing into very hot plasma (ranging from 12,000 to 23,000 degrees Fahrenheit) where the extracting solution is analyzed for the amount of phosphorus, potassium, calcium, magnesium, zinc, copper, manganese, boron, and sodium. The instrument is called an inductively coupled plasma (ICP). More about how the ICP works.

13 Data Preparation - The "blank" and "check" samples are reviewed for accuracy, and then the data is stored on a file and merged with the name and address information and other results according to lab number.

14 Scooping - The ph is determined on samples using a 1:1 ratio of soil to water (20 grams of soil and 20 gram water). We use the assumption that 16 ml of soil weighs 20 grams which is scooped into paper cups. Adding Water - A jet stream of 20 ml. deionized water is added to each sample. The samples are allowed to sit for at least 1 hour to allow time for them to equilibrate.

15 ph Meter - The ph value is measured using a calibrated ph meter. More about what ph is More about how the ph electrodes work Electrode Diagram Membrane Diagram Combination Electrode

16 Adding Water - A jet stream of 20 ml. deionized water is added to each sample. The samples are allowed to sit for at least 1 hour to allow time for them to equilibrate.

17 ph Meter - The ph value is measured using a calibrated ph meter. More about what ph is More about how the ph electrodes work Electrode Diagram Membrane Diagram Combination Electrode

18 Data Preparation - The check samples are reviewed for accuracy. The data from the meter is automatically stored into a file and then merged with the name, address information and other data.

19 Adding The Lime Requirement Solution - After the ph of the soil is determined, 20 ml of a lime requirement solution called the Adams Evans Buffer (guess who invented it?) is added and mixed with each sample. The samples are allowed to sit for 30 minutes then the ph is measured again.

20 ph Meter - The ph of the Adams Evans Buffer solution starts at 8.00 (which is in the alkaline range). The more the Adams Evans Buffer drops down from 8.00 after adding it to the soil, the more reserve acidity there is in the soil. The more reserved acidity the soil has, the more lime will be needed to raise the ph value to the target ph value. For More Information About Reserve Acidity

21 Data Preparation - The data from the meter is automatically stored into a file and then merged with the name and address information and other data.

Lime Table - Both the soil ph and the buffer ph values are used to determine the final lime recommendations. This table shows how much lime is required to bring the ph of a soil up to 6.

22 Lime Table - Both the soil ph and the buffer ph values are used to determine the final lime recommendations. This table shows how much lime is required to bring the ph of a soil up to 6.5. For example, if a soil (water) ph is 5.6 and the buffer ph is 7.8 the lime recommendation would be 1,500 lbs/acre. Print it as a pdf file, or click on the Lime Table for an enlargement.

23 Scooping - The soil nitrate-nitrogen (NO 3 -N) is determined by special request. This test is not included with standard plant elements because nitrate is so mobile in the soil that by the time the client receives the lab resu the nitrate levels in the soil may have already changed. The lab gives a "general" nitrogen recommendation o the soil test reports since, for most crop situations, there is little or no nitrogen left in the soil from the previo year s crop. The nitrate-nitrogen test is for trouble-shooting or research purposes. The samples are transferred into sample extraction containers using a 16 ml volumetric scoop and leveled with a Teflon bar for consisten volume. This represents approximately 20 grams of soil.

24 Extraction solution - Forty ml of the aluminum sulfate extracting solution is added to each sample, mixed thoroughly and then allowed to equilibrate for one hour.

25 Nitrate Meter - The NO 3 -N is measured by a nitrate sensing electrode, reference electrode, and meter. More about how the nitrate electrodes work

26 Data Preparation - The data is entered into a file and merged with the name and address information and other results according to lab number.

27 Scooping - Organic matter is determined by the loss on ignition method (LOI). This means the sample is heated to a very high temperature until all the organic matter is burned off and all that remains is the mineral soil. Approximately 5 grams of each sample is scooped into pre-weighed crucibles.

28 The Furnace - The samples are dried at 105 o C for 2 hours to drive off all the moisture. They are then weighed and heated to 360 o C for 3 hours to destroy the organic matter.

29 The Balance - The samples are weighed again. The percent organic matter (LOI) is calculated by the difference in weight before and after heating in the oven at 360 o C.

30 Data Preparation - The data is entered into a file and merged with the name and address information and other results according to lab number.

31 Scooping - Twenty ml of the sample is scooped into a 250 ml Erlenmeyer flask.

32 Water Addition - Forty ml of deionized water is added and then the sample is allowed to equilibrate for 1 hour by shaking intermittently.

33 Salinity Meter - The conductivity (which is another way of measuring the amount of salinity) is measured on the filtered extract using a conductivity meter and electrode. More about how the conductivity (salinity) meter works.

34 Data Preparation - The data is entered into a file and merged with the name and address information and other results according to lab number.

35 Scooping - Sulfur in the sulfate form (SO 4-2 ) is determined by special request. Like nitrates, it is very mobile the soil so the lab results will have very little meaning if the sample is taken from the soil surface for a sandy soil. The samples are scooped and leveled with a bar using a 4 ml volumetric scoop into sample extraction racks. Extraction solution - Twenty ml of the sulfate extracting solution (0.5 N ammonium

36 acetate in 0.25 N acetic acid) is added to each sample. Sulfur must be tested separately from the other minerals since the Mehlich 1 extraction solution contains sulfur from the sulfuric acid. Shaking - The samples are shaken for 5 minutes to ensure good soil and solution contact as well as adequate time to extract the sulfur.

37 Filtering - The soil and solution mixture is filtered through filter paper. The soil is trapped in the filter paper and the extracting solution with the now dissolved sulfatesulfur is collected in the tubes.

38 Transferring to test tubes - The extract that passes through the filter paper is transferred into test tubes.

39 The ICP - The extract is analyzed for sulfur using an inductively coupled plasma (ICP). The solution is pumped through tubing into the plasma. More about how the ICP works

40 Data Preparation - The data is entered into a file and merged with the name and address information and other results according to lab number.

41 Data Entry - The name and address information along with the desired analyses and crop and soil codes are entered into the database. The results from the ICP, ph, and other analyses are merged with the name and address information according to the lab number.

42 Generating Reports - The reports are hard copied or posted on the web for the client. The county Extension offices have web access to all reports for samples coming through their office.

For many crops recommendations can be obtained in lbs/acre or lbs/100 or

43 Report Format - The report for each sample includes results, calculations, and recommendations and comm for up to four crops. For many crops recommendations can be obtained in lbs/acre or lbs/100 or 1000 square by using different crop codes. Clemson Extension Agriculture Service Laboratory

Soil Sampling and Nutrient Recommendations. Kent Martin SW Agronomy Agent Update 12/1/2009

Soil Sampling and Nutrient Recommendations Kent Martin SW Agronomy Agent Update 12/1/2009 Outline How to take a soil sample What is the appropriate depth for soil tests How many should you take How often