What tests to order

Soil Health and Arthropods

Roughly speaking there are two distinct aspects to studying arthropods in the soil. The first, and most fundamental, is the interrelationship between the most abundant and diverse elements within the soil itself. Since these are true soil-dwellers, they are usually small and inconvenient to see with the naked eye. The principal role of these creatures, (to make a long story short), is to recycle nutrients and make them available for plants. These micro-arthropods may be extracted from a soil core.

The larger, and therefore less abundant, macro-arthropods which take refuge in the soil are usually active on the soil surface. They are of primary interest because they include most insect pests and the biocontrol predators necessary for system stability. Though they may number in the millions, the number within any one soil core is insufficient for analysis. Therefore, these highly mobile creatures have to trap themselves for analysis. Simple pitfall trapping does the trick. These macro-arthropods are easy for you to keep track of by yourself, once you learn from us what the different species are and what they do.

Procedure for Macroarthropod Samples

Samples of the larger arthropod fauna are most easily accomplished with pitfall traps. Since pitfall traps can be run in any number of ways, we can interpret them only if they are standardized. To standardize captures: run the pitfall trap for 1 week; and use rubbing alcohol or antifreeze as a preservative. Any number of traps can be run simultaneously and added together before sending them to us for analysis. (Keep track of how many traps were run).

The Trap:

1. Obtain a plastic food container (margarine tub; 1 pt or 1 qt yogurt; etc).
2. Bury the food container up to its lip in the soil to be tested. Pack the soil tightly around the plastic tub so that the ground-dwelling insects will have no difficulty walking to the edge to investigate and then falling in.
3. Remove any dirt that fell into the trap while you were setting it. Place about ¸ inch of antifreeze or ¸ inch of rubbing alcohol into the bottom of the trap. The antifreeze wont evaporate, but the alcohol will and you will have to add more alcohol every 2nd or 3rd day.
4. Design some sort of roof to cover the trap that will prevent rain from getting in and diluting the preservative, while still allowing the insects to enter. It is probably easiest to find a square of waste plastic or a square of corrugated cardboard several inches wider than the diameter of the plastic tub. Place a 2-3 inch nail through each of 2 adjacent corners of the cardboard and push them partly into the dirt - then you have a sloping roof that will keep the rain off for the week of trapping.
5. After a week, remove the trap from the ground and secure the top. You can add together any replicate traps at this time. Before you mail it to us, be sure to secure the top with tape. If the plastic container will fit into a ziplock bag please enclose it. Tops have a habit of coming off during mailing and making a terrible mess. If you have more than one sample from more than one place, be sure to label them appropriately.

Procedure for Microarthropod Samples

1. Samples must be 10 inches square and 2 inches deep. If the samples are from an area with a litter layer, the litter layer must be included in addition. (Therefore the sample core must extend into the soil itself to a depth of 2 inches.)
2. Samples must be placed in a ziplock sealed plastic bag.
3. Samples need to be protected from any excessive heat or protracted time in shipping. 2-3 days in an uninsulated box is maximal; shipment in an insulated container in overnight mail is preferred.
4. When multiple samples are being sent, care must be taken against compaction of the soil during transit. Send no more than 5 samples in a box; do not place more than two layers of samples on top of one another. (Soil critters are delicate.)

Procedure for Extracting Soil Microarthropods

1. Be sure that FSI reference number is available before proceeding.
2. Place metal funnel apparatus upright, over a completely empty Ball jar, on the counter next to the sink.
3. Empty the sample bag into the funnel. If the sample is not of a consistently fine structure, the clods must be TENDERLY broken up to allow for complete and even drying. (Anybody living in a clod which dries from the outside will simply go to the center of the clod and be dessicated in situ, without migrating to the bottom and through the mesh.)
4. If the sample is especially voluminous, say it contains a large amount of litter, then it should be divided into two separate extractors - each given an a, b designation.
5. Take a new Ball jar, label it TWICE with SFI number with Sharpie, and place ¹ inch of antifreeze in bottom.
6. Place funnel in rack. Empty any of the soil that passed through into the first Ball jar into the top of the funnel.
7. Place the correctly labeled Ball jar with antifreeze under the funnel on the apparatus. (Screw it on.)
8. Repeat procedure with any additional samples.
9. Record date of sample setup on permanent record.

General Notes:

1. Keep samples to be processed in portable plastic coolers. Do not compress samples.
2. Keep an eye on the reserve of antifreeze.
3. Keep an eye on the reserve of light bulbs.
4. Please call first before submitting Arthropod samples.

For more information, contact Dr. Andrew Moldenke 541-737-4596.

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