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Soil biological testing at Ward Laboratories is conducted by analyzing phospholipid fatty acids, or PLFA. PLFA gives a representation of living soil microbial biomass and allows us to identify the presence or absence of various functional groups of interest through known PLFA biomarkers. PLFA is a snapshot of soil community structure and abundance at the time of sampling. As environmental conditions such as temperature and moisture change so does the microbial community. This ability of the soil microbial community to change provides producers with a tool to compare agricultural management techniques with respect to overall better microbial community health.

General Information

Soil is a complex ecosystem that provides habitat for an endless array of micro and macro organisms. These include bacteria, fungi, protozoa, nematodes, earthworms, etc. These organisms are responsible for much of the nutrient cycling that takes place in the soil. They provide the breakdown of crop residues, store plant nutrients, create stable organic matter in the form of humic acid, and help build soil structure, thus leading to reduced compaction and erosion, while increasing water holding capacity and allowing for deeper root structures. The relationship between different microorganisms and plants is dynamic. The predatory action of protozoa on bacteria helps release nitrogen into the soil and symbiotic bacteria and fungi aide the plant in acquiring more nutrients. Through better understanding of soil microbial communities we can begin to allow these organisms to work for us in our goal of high yielding, sustainable agriculture.

Soil microbial community testing at Ward Laboratories is conducted by analyzing phospholipid fatty acids or PLFA. These fatty acids are found in the cell membranes of living organisms, from bacteria to plants and animals. However, they degrade relatively quickly in the soil when an organism dies and the membrane begins to break down. These characteristics make extracting and quantifying PLFA from the soil a powerful tool for estimating living microbial biomass. In addition, PLFA biomarkers, or signature fatty acids, allow us to identify the presence or absence of various functional groups of interest such as different bacterial groups, actinomycetes, arbuscular mycorrhizal fungi, rhizobia, protozoa, etc. PLFA is a snapshot of community structure and abundance at the time of sampling. As environmental conditions such as pH, temperature, and moisture change so does the microbial community. These communities are also influenced by soil type, organic matter, intensity and type of tillage, crop rotations, cover crops, and herbicide or pesticide applications. The ability of microbial communities to change rapidly provides producers with a tool to compare agricultural management techniques with respect to overall better soil health and fertility.

Soil fertility and biological tests can be run on any soil samples you wish. However, there is no baseline for biological testing as there is for chemical analysis. Therefore, this test is most useful in making comparisons between management conditions. The list of management conditions can be anything you are interested in, perhaps till vs. no-till, different fertilizer applications, crop rotations, various mono cover crops or mixes, grazing vs. no grazing, etc. The main focus is to compare various agricultural techniques and their effects on soil microbiology as well as fertility. Trying to tie the two related, but different, forms of testing together for sustainable farming is the main goal.

Additional information will be added to the website as new information becomes available. Any questions regarding biological testing may be directed to biotesting@wardlab.com.

Sampling Information

Sampling for biological testing is slightly different than regular soil testing. It is very important to treat all the samples equally. Listed here are general guidelines to sample for biological testing:
  1. Collect all of your samples for comparison on the same day if possible. Samples may be collected on different days but try to keep sampling events to one week or less if comparisons are to be made between the samples. This reduces changes that may take place if moisture or temperature fluctuates between sampling times.
  2. Use a standard soil core sampler. DO NOT use any form of lubricants on the soil core sampler.
  3. Take 10-15 cores roughly 0-8 inches deep next to the plants or near the rooting structures. You may also choose the same depth that is normally used for a topsoil sample as long as it is consistent.
  4. Combine all the cores, preferably in a zip lock freezer bag or plastic-lined paper soil bag. DO NOT use cloth bags for submitting samples.
  5. Add all sample identification information you need to the sample bag and place in a cooler (A Styrofoam cooler with a lid works fine) or a regular box if shipment times are relatively quick.
  6. Mark each sample and the shipping container BIOTESTING or PLFA to ensure proper handling on our end.
  7. We would like samples to remain near original soil temperature if left unfrozen. Ice packs can be used if sampling during hot weather. Remember to treat all samples equally for individual sampling periods.
  8. Samples may be frozen in a standard freezer for storage prior to shipment. This is especially useful and should be done if samples are being taken at different times.
  9. Samples can be mailed to or dropped off at Ward Laboratories Inc, 4007 Cherry Avenue, Kearney, NE 68848. When mailing samples it is best to send them overnight in a cooler if not previously frozen. However, samples can be sent frozen in a cooler by regular mail in mild or cold weather.

Additional information will be added to the website as new information becomes available. Any questions regarding biological testing may be directed to biotesting@wardlab.com.

Report Example (PDF)


List of Peer-reviewed References used for PLFA/FAME Analysis at Ward Laboratories, Inc.

*Not peer-reviewed reference material.

BOLD References – Significant Importance

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