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Characterizing soil samples for populations of fungi and bacteria helps growers evaluate soils for various crops - and identify needed microorganisms.
STUDYING the results of soil and plant tissue analyses was routine for Jim Barlow a crop nutrition consultant for large-scale farms in California's Central Valley and the Northern Willamette Valley of Oregon, but often he felt they were giving him an incomplete picture of what was happening in the soil. "I was trying to solve crop production problems, and frequently, after studying soil chemical and physical characteristics and plant tissue analyses, I would realize that something else had a grip on the crop," he says.
Barlow figured that the key to the problems was related at least in part to biology, which was not revealed by standard chemical analysis of soil and plant tissue. He sought out Elaine Ingham, who had established the Soil Microbial Biomass Service (SMBS) at Oregon State University in Corvallis in 1991 to test forest, farm and prairie soils. SMBS also managed a database to guide farmers and ecologists in soil restoration and improving plant health and agricultural productivity.
Ingham had become interested in soil microbial dynamics in graduate school in 1981, and during the course of her career has analyzed over 25,000 soil samples for microorganism biomass (total body weight of organisms) and activity and correlated this information to soil chemistry and plant growth. In 1993, Barlow started taking samples to SMBS, and applying Ingham's knowledge to the challenges facing farmers.
IMPACT OF SOIL MANAGEMENT PRACTICES
Populations of soil bacteria and fungi are sensitive to soil management practices. Frequent cultivations practiced by row crop farmers create an environment that favors bacteria, which are small, simple organisms that can easily survive disturbance. No-till orchard and vineyard systems favor fungi, which have long thread-like bodies easily broken by cultivation. Fungi are more tolerant of low moisture conditions. Predator nematodes and protozoa feed on bacteria and fungi, and in the process supply plant-available nitrogen to crops. Generally, as food web complexity increases, crop productivity improves.
As demand for the analytical services of SMBS grew, it became apparent that they could be provided more economically by a private laboratory, without the overhead required by university administration. "The university is in the business...