Author
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Pratt, Robert |
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Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/19/2007 Publication Date: 2/1/2008 Citation: Pratt, R.G. 2008. Fungal population levels in soils of commercial swine waste disposal sites and relationships to soil nutrient concentrations. Applied Soil Ecology. 38:223-229. Interpretive Summary: It has long been known that repeated applications of large quantities of waste materials from concentrated swine, poultry, and cattle feeding operations to the same agricultural lands for many years may overload soil with nutrients and initiate several forms of water and air pollution. Much less is known of whether or how such repeated animal waste applications affect microbial populations in soil, and especially populations of soil fungi. These microorganisms are important to soil ecology because they break down organic matter, recycle nutrients between soil and plants, and serve as repositories for large quantities of soil nutrients within their structures. Therefore, this study was undertaken to determine whether years of commercial swine waste applications to pasture soils in Mississippi affect fungal populations in soil. In three years of sampling similar soils, with and without swine waste applications, on three commercial swine farms in Mississippi, and measuring fungal population levels by dilution plating of soil on agar, no strong or consistent effects of the waste applications on population levels of total fungi or of seven individual species in soil were observed. Major differences in concentrations of some soil nutrients, up to five- to 10-fold, were found between soils with and without swine waste applications, but these nutrient concentrations were not related to fungal population levels. It is concluded from this study that although repeated swine waste applications may deleteriously affect some properties of soil, air, and water that can lead to environmental pollution, no deleterious effects are evident on fungal population levels in soil. Technical Abstract: Little is known of how commercial applications of animal wastes to agricultural soils affect soil microbial populations. This study was undertaken to determine whether commercial applications of liquid swine waste to pasture soils in Mississippi, USA, influence fungal population levels in soil, and whether these are related to soil nutrient concentrations. Colonies of filamentous fungi were assayed by dilution plating from samples of soil with and without applied swine waste that were collected from pastures on three commercial farms in northeast Mississippi. Samples were collected early and late in the summer growing season during each of three years. Mean fungal population levels observed in 180 samples were 2.80 - 43.27 x 104 colony-forming units per gram of soil. Significant differences between waste treatments were observed in only 2 of 18 sampling events (3 years x 2 times x 3 sites) when populations were both higher and lower in waste-treated than in untreated soils. Population levels of Aspergillus, Fusarium, Penicillium, and Trichoderma spp. also did not differ significantly between waste treatments in more than 2 of 18 sampling events. Concentrations of P, K, and Na were always significantly greater, often by factors of 5-10-fold, in waste-treated than in untreated soils; levels of Mg, Cu, and Zn were frequently greater; and levels of Ca, Fe, and Mn were seldom or never greater. However, fungal population levels were not correlated with concentrations of any of these nutrients in more than 2 of 18 sampling events. Results indicate that total fungal population levels, and those of 7 individual population components, usually are not affected by commercial applications of liquid swine waste to pasture soils in Mississippi. |
