University of Arkansas - AgriScience Project

AGRISCIENCE EXERCISE

PHYSICAL SCIENCES IN AGRICULTURE/ENVIRONMENTAL RESOURCE SYSTEMS

Sub-Concept: Understanding Soil & Water / Soil Fertility

Agricultural Context: Soil Testing & Analysis

Exercise: Interpret Results of Commercial Soil Analysis

Goals:

1. Describe the purpose of soil testing.
2. Name the agency responsible for soil testing.
3. Interpret an information sheet received from a soil testing facility.
4. Calculate cost of following recommendations given on soil analysis information sheet.

Materials:

• Soil test information sheets
• Soil sample cartons
• Soil samples from previous exercise

References: Instructional Materials Service. (1994). Commercial Soil Testing Procedures Lesson Plan. IMS, Texas A & M University, College Station, TX.

Teacher Preparation Notes:

• You may wish to send in two cartons of one sample, designating that one is intended for crop production and the other for a lawn. The recommendations can then be compared to show students the importance of completely and properly filling out the preliminary information.

Procedures for Conducting the Activity:

2. Complete the soil test information sheet provided by the testing agency.

3. Take all samples to the testing agency.

5. When results are returned, discuss the following items:

a. What information is provided on the analysis sheet?

b. What recommendations are made for improving the soil?

6. Calculate the cost of carrying out the recommendations made. Call local fertilizer dealers to obtain needed price information.

COMMERCIAL SOIL TESTING

PURPOSE

- Soil testing indicates the amounts of various plant nutrients present in the soil in forms available for plant use

- Soil tests serve two primary functions:

1. As a diagnostic tool, soil tests show certain problems such as salinity, excess acidity or alkalinity, and nutrient imbalance. Soil tests do NOT indicate physical properties of a soil or the presence of insects or diseases.

2. Soil tests give suggestions for applying plant nutrients. These recommendations are based on the nutrient levels in the sample, the crop to be grown, cropping history, past yields, past fertilizer applications, irrigation and liming practices, and expected or desired yields. So, information provided through a soil analysis helps a producer make better and more profitable soil management decisions.

TECHNIQUES OF SOIL TESTING

- Commercial testing laboratories generally use chemical testing methods to measure the amounts of plant nutrients available in the soil.

- Some instruments used include:

a. pH meters to measure alkalinity/acidity levels

b. photoelectric colorimeters to determine phosphorus content

c. flame photometers to measure potassium and sodium levels

d. atomic absorption spectrophotometers to indicate the amounts of calcium magnesium, and micro-nutrients (manganese, iron, copper, and zinc)

- Some computerized soil analysis systems are now being developed to provide faster and better soil analyses.

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