LaMotte STH User Manual

Model STH Series

Combination Soil Outﬁ t

Instruction Manual

Introduction ............................................................. 4

Multiple Sample Testing Test Methods Available Nutrients Soil Sampling & Preparation Test Procedure

pH ............................................................................ 6

Extraction ................................................................ 7

Nitrate Nitrogen ....................................................... 8

Potassium ................................................................ 8

Phosphorus ............................................................. 10

Humus .................................................................... 11

Magnesium ............................................................. 12

Calcium .................................................................. 13

Sulfate .................................................................... 14

Aluminum .............................................................. 14

Chloride .................................................................. 15

Ferric Iron .............................................................. 16

Nitrite Nitrogen ...................................................... 16

Ammonia Nitrogen ................................................ 17

Manganese ............................................................. 18

Units of Measure Fertilizer Application Rates Green Plant Tissue Tests Soil Test Reagents

........................................................... 5

......................................................... 6

..................................................... 19

............................................ 5

.................................................... 5

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....................................... 19

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Introduction

This instruction manual is designed for use with the LaMotte STH Series of professional soil testing outﬁ ts. The basic Model STH-4 Outﬁ t (Code

5029) tests soil for pH, nitrate nitrogen, phosphorus, and potassium. Intermediate STH outﬁ ts combine these four tests with tests for other important plant nutrition factors (humus, calcium and magnesium). The Model STH-14 Outﬁ t (Code 5010-01) analyzes for all of the factors listed above, along with tests for ammonia nitrogen, manganese, aluminum, nitrate nitrogen, sulfate chloride and ferric iron. This manual also includes special instructions for testing nitrate, phosphorus, and potassium in green plant tissues.

*WARNING: Reagents marked with an * are considered to be potential health hazards. for these reagents go to www.lamotte.com. To obtain a printed copy, contact LaMotte by e-mail, phone or fax.

Note: Some reagents in this kit are dispensed with screw-cap pipets that are packaged separately.

Place the screw-cap glass pipets (0341) on the following reagents:

5156 *Phosphorus Reagent #2 5101 *Aluminum T est Solution 5140 *Magnesium Test Solution #1

To view or print a Material Safety Data Sheet (MSDS)

Place the screw-cap plastic pipets (0392) on the following reagents:

5146 *Nitrate Reagent #1 5108PS *Calcium T est Solution 5171 *Sulfate T est Solution 5116PS *Ferric Iron Test Solution 5103PS *Ammonia Nitrogen Test Solution

Multiple Sample Testing

When extracts from two or more samples are being tested simultaneously use separate pipets for each extract. Mixing samples will cause false test results. Multiple test tubes, pipets, and spot plates have been provided to facilitate proper analytical technique.

Test Methods

Color chart methods are used for all tests except for Potassium. The reaction is performed in a tube or on a spot plate and the resulting color is compared to a laminated color chart.

The Potassium test measures the amount of turbidity in a sample relative to the potassium content.

Available Nutrients

All tests measure the portion of the nutrient in the soil that would be “available” for the plant to use. Since extraction is not complete, the amount that is measured is relative, dependent on the extraction procedure.

Soil Sampling & Preparation

Carefully follow the soil sampling procedures discussed in detail in the LaMotte Soil Handbook (1504). For sampling greenhouse soils, the following specialized procedure is recommended.

Collect greenhouse samples prior to watering. Remove any mulch covering the soil, and then use a soil sampling tube or spoon to take a sample from the entire plant rooting space, top to bottom. A composite sample insures representative test results. Thoroughly mix 8 to 10 individual samples, and then spread the composite sample on a sheet of paper or plastic to dry. Allow the sample to air dry overnight. Do not oven dry the sample. Sift the dried sample through a wire screen mesh similar to a window screen.

Test Procedures

pH is a measure of acidity or basicity. Soils can have a pH from 3.5 to

11.0, but plants grow well in the range of 5.0 to 8.5. In soils with a low pH (acidic), some nutrients can reach toxic levels and the activity of soil microbes is greatly reduced. Soils with a high pH (alkaline) generally have a lower micro-nutrient availability and some levels may be deﬁ cient.

PROCEDURE

1. Fill a test tube (0204) approximately one-third full of soil. Use the Demineralizer Bottle (1155) to add demineralized water to the

until it is ﬁ lled to one-half inch from the top. Cap and shake

tube, until the

soil is well dispersed.

2. Add 5 drops of Soil Flocculating Reagent (5643WT). Cap and shake to mix. Allow contents to settle before proceeding to Step 3.

3. Use a 1 mL pipet (0354) to transfer 1 mL of the clear solution above

the soil to one of the large depressions on a spot plate (0159).

Transfer

a second 1 mL sample to the other large depression on the

spot plate.

4. To the ﬁ rst sample on the spot plate, add two drops of *Duplex Indicator (2221). Compare the resulting color reaction against the Duplex Color Chart (1313).

5. The wide range pH test result indicates which narrow range indicator and color chart should be selected to perform a more precise pH test. Choose the narrow range indicator and appropriate chart with a mid-point that is as close as possible to the value obtained in the wide range test.

Indicator pH Range

Bromcresol

3.8-5.4 2207 1328

Indicator

Code

Color Chart

Green Chlorphenol

5.2-6.8 2209 1329

Red Bromthymol

6.0-7.6 2210 1331

Blue Phenol Red 6.8-8.4 2211 1332 Thymol Blue 8.0-9.6 2213 1335

Example: If the wide range test result is pH 6.0, choose the Chlorphenol Red Indicator (2209) & the Chlorphenol Red Color Chart (1329) for Step 5.

Code

6. Add two drops of the chosen narrow range indicator to the second sample on the spot plate. Compare the resulting color reaction against the appropriate color chart to obtain a precise soil pH reading.

Interpretation of pH Reading:

If the pH is Then the soil is

Below 5.5 Strongly Acid

5.5-6.0 Moderately Acid

6.1-7.0 Slightly Acid Above 7.0 Alkaline

Extraction

The following extraction procedure uses *Universal Extracting Solution (5173PS) to produce a single soil extract which is used in each of the following tests: nitrate nitrogen, ammonia nitrogen, nitrite nitrogen, phosphorus, potassium, calcium, magnesium, sulfate, aluminum, iron, and manganese. The pH, chloride, humus, and plant tissue tests use extraction procedures described in the individual instructions for those tests.

The Extraction Tubes (0704) are marked at 7 and 14 mL. The instructions below assume that a number of tests will be performed with the general soil extract. Therefore 14 mL of extracting solution and eight level measures of the soil sample are called for in Steps 1 & 2. If only a single test is to be performed (e.g., nitrate nitrogen), ﬁ ll the extraction tube to the 7 mL line (Step 1) and add only four level measures of the soil sample (Step 2).

PROCEDURE

1. Fill an Extraction Tube (0704) to the 14 mL line with *Universal Extracting Solution (5173PS).

2. Use the 0.5 g spoon (0698) to add eight level measures of the soil sample. Cap and shake for one minute. Note: When adding samples with high concentrations of carbonates to the *Universal Extracting Solution (5173), swirl tube to mix for 30 seconds before capping to allow gases to escape.

3. Use a piece of ﬁ lter paper (0465) and a plastic funnel (0459) to ﬁ lter the soil suspension into a second extraction tube (0704). (Fold the

ﬁ lter paper in half and then in half again to form a cone which is ﬁ tted into the funnel.) The ﬁ ltrate in the second extraction tube is

the general soil extract for use in the 11 individual test procedures listed previously.

Nitrate Nitrogen

The role of nitrogen in plant nutrition is discussed in the LaMotte Soil Handbook. For interpretation of test results see the LaMotte Soil Handbook.

PROCEDURE

1. Use a 1 mL pipet (0354) to transfer 1 mL of the general soil extract to one of the larger depressions on a spot plate (0159).

2. Add 10 drops of *Nitrate Reagent #1 (5146).

3. Use a 0.5 g spoon (0698) to add one level measure of *Nitrate Reagent 2 Powder (5147).

4. Stir thoroughly with a clean stirring rod (0519). Allow to stand ﬁ ve minutes for full color development.

5. Match sample color with the Nitrate Nitrogen Color Chart (1315). Record as pounds per acre nitrate nitrogen.

Potassium (Potash)

The role of potassium (potash) in plant nutrition is discussed in the LaMotte Soil Handbook. For interpretation of test results, see the LaMotte Soil Handbook.

When present in large amounts, ammonia salts will produce a precipitate similar to that produced by potassium. If fertilizer containing ammonia salts has recently been applied, or if the soil pH is below pH 5.0, perform the Ammonia Nitrogen test (page 19) before performing the potassium test. A high ammonia nitrogen test result will alert the operator to a probable false high reading in the potassium test; actual potassium levels will be somewhat lower.

It is important that the temperature of the test sample and the *Potassium Reagent C (5162) be in the range of 20-27°C (68-80°F). On warm days, prior to Step 3 below, cool both the test sample in the Potash “A” Tube and the Reagent C container by placing them in cool water.

PROCEDURE

1. Use a transfer pipet (0364) to ﬁ ll a Potash “A” Tube (0245) to the lower line with the general soil extract.

2. Add one *Potassium Reagent B Tablet (5161A). Cap and shake until dissolved.

3. Add *Potassium Reagent C (5162) until the Potash “A” Tube is ﬁ lled to the upper line. Allow the *Potassium Reagent C (5162) to run slowly down the side of the tube. Swirl the tube to mix. A precipitate will form if potassium is present.

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