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ARS Home » Pacific West Area » Pendleton, Oregon » Columbia Plateau Conservation Research Center » Research » Publications at this Location » Publication #64922
Title: SOIL QUALITY AND SOIL ORGANIC MATTER.

Author
item Albrecht, Stephan
item Rasmussen, Paul

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: Recent interest in sustainable agricultural has brought renewed attention to soil quality and soil organic matter. Soil quality is a complex concept. Soil organic matter is a significant part of soil quality. In most soils, humus is the largest fraction of Soil Organic matter. Humus fraction is especially important as it provides soil structure, pH-buffering and water and mineral-holding capacities. The largest source of organic material entering the soil comes from plant residues. Soil organic matter is lost either by biological oxidation or erosion. Agricultural practices that remove plant material, such as burning, grazing or harvesting part of the cultivated crop for human or animal feed, decrease soil organic matter levels. In long-term plots at the Columbia Basin Agricultural Experiment Station, annual addition of manure to a wheat-fallow rotation has maintained a soil organic matter content roughly equal to that of annually cropped soil receiving moderate inorganic fertilizer application. Erosion is very incompatible with maintaining soil organic matter. Soil organic matter is difficult to accurately measure. It is generally estimated by relatively harsh treatments which actually measure soil carbon quantity, however they do not determine organic matter quality, and are of limited value. A greater understanding of how management practices affect soil organic matter will contribute significantly to sustainable agriculture and soil health. More information is needed on how soil organic matter responds to crop rotations, fertilization, and other management practices.

Technical Abstract: Recent interest in sustainable agricultural has brought renewed attention to soil quality and soil organic matter (SOM). Soil quality is a complex concept. Soil organic matter is a significant part of soil quality. In most soils, humus is the largest fraction of SOM. The humus fraction is especially important as it provides soil structure, pH-buffering and water and mineral-holding capacities. The largest source of organic material entering the soil comes from plant residues. Soil organic matter is lost either by biological oxidation or erosion. Cultivation of grassland soils commonly causes the loss of one-third to one-half of the native SOM in the first 40-60 years. Agricultural practices that remove plant material, such as burning, grazing or harvesting part of the cultivated crop for human or animal feed, decrease SOM levels. In long-term plots at the Columbia Basin Agricultural Experiment Station, annual addition of manure to a wheat-fallow rotation has maintained a SOM content roughly equal to that of annually cropped soil receiving moderate inorganic fertilizer application. Erosion is very incompatible with maintaining SOM. Soil organic matter is difficult to accurately measure. It is generally estimated by relatively harsh treatments which actually measure soil carbon quantity, however they do not determine organic matter quality, and are of limited value. A greater understanding of how management practices affect SOM will contribute significantly to sustainable agriculture and soil health. More information is needed on how SOM responds to tillage practices, crop rotations, residue, fertilization, and other management practices.