PLFA Information

PLFA 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 Lance Gunderson at Lgunderson@wardlab.com