AGRONOMIC DIVISION, NORTH CAROLINA DEPARTMENT OF
AGRICULTURE TOUR
LABORATORY EXERCISE #10
OBJECTIVES

Learn the services provided by the NCDA Nematode, Soil, Plant, Waste and Solution
Testing Laboratories.

See what happens to the soil samples you send to the lab.

Be able to answer all the questions at the end of this laboratory exercise.
I NTRODUCTION
Providing adequate nutrients is essential for successful plant production whether it he for ornamentals, field crops, animal feed, or greenhouse crops. The selection of appropriate nutrient addition requires knowledge of the nutrient needs of the crop to be produced and the nutrient supplying ability of the soil or growing medium in which the crop is to be grown. Soil and plant testing procedures have been developed to:
1. Determine the nutritional requirements of crops.
2.Determine the nutritional supplying ability of soils.
3. Identify nutrient deficiencies in soil and plant material.
The North Carolina Department of Agriculture provides soil and plant testing free of charge as a service to residents of the state. Results of analysis are reported along with general management recommendations. Today you will learn about the Nematode Lab, Soil Testing lab, and Plant
Tissue Testing Lab to see how this information is obtained.
NEMATODE LABORATORY
Nematodes are microscopic worm-like animals found in almost all soils. Nematodes can be grouped into 3 types:
1.
Those that live on decaying organic matter
2.
Those that attack and kill nematodes and other microorganisms
3.
Those that are parasites, attacking plant roots
It is this third group that contributes to crop losses, in both the field and the greenhouse. The current (1994) estimate of annual losses to North Carolina agriculture from nematode damage is
$100 million dollars. The NCDA provides the Nematode Advisory Service to producers so that nematode levels can be monitored. If the levels indicate that crop damage may occur, control measures are recommended.
1

As with soil and plant samples, analysis and recommendations for nematodes is only as good as the soil sample and information given about the soil sample. The nematode lab CANNOT use a soil sample sent in for nutrient analysis. A separate sample must be submitted for nematode analysis. Carefully read and follow the directions on the information form for collecting soil samples for nematode analysis. Remember that nematodes are living creatures that must be kept alive in the sample for the lab to count them. Dead nematodes can't be counted.
Once samples are received by the lab, nematodes are separated from the soil by washing the soil with water. The nematodes are collected, washed again, and placed on microscope slides. A microscope is used to identify and count the nematodes. The lab reports the kind and numbers of nematodes found in the sample and, if needed, suggests general recommendations for control.
You now need to visit the Nematode Assay Section of NCDA’s Virtual Tour. Follow the link
( http://www.ncagr.com/agronomi/Nemas/sld001.htm
) to view the slideshow of how samples are processed for nematode assay.
LABORATORY ACTIVITY
Answer all of the following questions. The instructors copy will be turned at the end of the field trip.
1.
Are all nematodes found in the soil harmful to crops?
2.
What signs tell me my plants may have a nematode problem?
3.
When is the best sampling time? When should samples NOT be taken?
4.
What are some general control methods?
5.
Are there certain crops that are especially susceptible to nematodes?
Soil Sampling : The Key to Reliable Soil Test Information
Soil Sampling for Home Lawns and Gardeners
2

SOIL FERTILITY LABORATORY
The next stop on our tour is the Soil Testing lab. Soil testing is done to estimate levels of plant nutrients in the soil and to determine pH and organic matter levels so fertilizer and liming recommendations can be made.
SAMPLE PREPARATION:
The sample preparation room is where the soil samples are prepared for analysis. Samples are given a lab number and then dried and ground. It is at this stage that the information about the sample is entered into the lab computer to later be used in the recommendations. These recommendations are only as good as the soil sample and the information given about the sample. It is important to take soil samples correctly and carefully, and thoughtfully fill out the information sheet that accompanies the sample.
The sample information sheet explains best sampling methods and instructions for completion.
For best recommendations, it is important to READ AND FOLLOW THE INSTRUCTIONS on the sample information form.
6.
Should I keep a record of my sample number and area sampled?
7.
Why is proper sample collection important?
8.
When should I sample and how long does it usually take before I receive test results and recommendations?
9.
Why is liming history important?
10.
What equipment should not be used to sample soils?
The next stop is where the soil samples are measured out for analysis. 3 samples are prepared: 1 for pH and liming recommendations; 1 for nutrient content; and 1 for humic matter content. In
North Carolina, a volume of soil is measured out rather than a weight of soil. This is because soils with a wide range of different weights per unit volume are found in North Carolina. For accurate results it is important that the same volume of soil be used for each soil tested. If samples of the same weight were used, samples of peat and muck would be very large and samples of sands would be very small. When a volume measure is used all the samples are the same size, and soil test results are more accurate.
3

The next step in soil testing is to determine the amount of nutrients available to plants that are already in the soil. To do this, a chemical extracting solution is added to the soil sample. It remove' a portion of the nutrients in the soil and holds them in solution so they can be measured.
After the extractant is added to the soil sample, the mixture is shaken for 10 minutes to allow time for soil nutrients to be brought into solution. Then the solution is analyzed to measure the amount of nutrients it contains. Also in this room, the other two soil samples are analyzed. The pH and buffer acidity are measured on one sample to estimate the lime requirements. The other sample is use to measure percent humic matter.
Before answering the remaining questions in the soil fertility section, let’s visit the Soil Testing
Sectionof the Virtual Tour. Follow the link ( http://www.ncagr.com/agronomi/Soil/sld001.htm
) to learn more about how soil samples are processed for soil fertility testing.
11.
How much does it cost to have a soil sample analyzed?
12.
What nutrients are removed by the extractant?
13.
What is the "lime requirement"?
14.
Why is humic matter tested rather than organic matter?
15.
How does the amount of humic matter relate to the amount of nutrients the soil can contain?
PLANT TISSUE, WASTE AND SOLUTION LABORATORY
After a crop has started to grow, nutrient deficiency symptoms can sometimes appear. These deficiencies can be corrected, but first the plant tissue must be analyzed. Plant tissue analysis can be used to monitor a crop during the growing season to ensure that soil nutrient levels are adequate for proper growth and to positively identify plant nutrient deficiencies. Plant material is prepared for analysis by drying and grinding. It is then dissolved in acid and the amounts of nutrients in solution are measured. As with soil samples, the results of plant testing are only as good as the sample. Sample size, portion of the plant sampled, and time of sampling vary with crop. It is important to READ AND FOLLOW THE INSTRUCTIONS on the information form that accompanies the plant sample.
The last section of the Virtual Tour is the Plant/Waste/Solution Section. Follow the link
( http://www.ncagr.com/agronomi/PWS/sld001.htm
) to learn more about how plant material, waste material, and solutions are processed for analyzing.
4

18.
Is routine plant sampling recommended?
19.
When sending in samples for plant tissue analysis, what type of samples should you send in?
5

6