Author
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Albrecht, Stephan |
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Rasmussen, Paul |
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Skirvin, Katherine |
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Goller, Roger |
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Submitted to: Pendleton Station Field Day
Publication Type: Experiment Station Publication Acceptance Date: 4/28/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Soil organic matter, especially humus, is desirable because it has many beneficial properties. It helps the soil hold water and fertilizers. Because soil organic matter is so beneficial to farming, it is important to understand the conditions that affect this material. The wheat residue that remains on the ground following harvest contributes to soil organic matter. However, many farmers in the Pacific northwest burn wheat residue. The farmers claim that burning offers disease and weed control, and improves tillage efficiency. Recently there have been suggestions that burning will increase soil organic matter. While fire is an efficient method to reduce crop residue to manageable levels, and may reduce weeds and disease, burning produces deleterious side effects, including increased air pollution and soil erosion. Research is being conducted on the effects of burning on soil organic matter and soil biological activity, essentially the ability of soil organisms to convert wheat straw into humus. The addition of wheat residue increased biological activity by soil organisms while the addition of burnt residue failed to stimulate this activity. Although burning residue may increase the carbon content in soil, it is unlikely that the burnt residue can be considered soil organic material - even though it may be reported as such by some laboratory tests. Field burning can contribute to lower soil biological activity, which may lead to decreased organic matter, increased soil crusting and erosion. Technical Abstract: The maintenance of organic matter, especially humus, in soils is desirable for long-term land use because of many beneficial effects including improved nutrient status, water holding capacity and structure. It is important to understand the factors, both physical (abiotic) and biological that affect soil organic matter. Many farmers in the Pacific northwest burn wheat residue. The reasons offered for burning include: 1. disease control; 2. weed control; 3. improved tillage efficiency; 4. reduced immobilization of nitrogen fertilizer and 5. sociological precedents. Burned residues, including partially burned straw are eventually incorporated in the soil where microorganisms use them for energy. Recently there have been suggestions that burning will increase soil organic matter. While fire is an efficient method to reduce crop residue to manageable levels, and may reduce weeds and disease, burning produces deleterious side effects, including increased air pollution and soil erosion. Research is being conducted on the effects of burning on soil organic matter and soil biological activity. The addition of wheat residue quickly immobilized nitrogen and decreased nitrogen mineralization while the addition of burnt residue did not. The addition of burnt residue did not increase the biological activity (respiration) of the soil microorganisms as much as the addition of wheat residue. Although a burn event may increase "soil carbon" it is unlikely that the burnt residue can be considered organic material - even though it may be reported as such by some soil tests. Field burning can contribute to lower soil biological activity, which may lead to decreased organic matter, increased soil crusting and erosion. |
