|DOUGLAS, JR, CLYDE|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/2000
Publication Date: N/A
Technical Abstract: Moldboard plowing, frequent fallowing, crop residue removal, and soil erosion make soils susceptible to organic matter loss in the semiarid regions of the Pacific Northwest. Maintaining soil organic carbon and nitrogen is essential for long-term sustainable agriculture -- thus there is an interest in the capacity of soil to sequester carbon. Changes in soil carbon and nitrogen in long-term experiments, with differing tillage and crop rotations, were investigated. The major factors influencing changes in organic carbon were the frequency of summer-fallow and the amount of carbon input by crop residue. While decreasing tillage intensity reduced soil carbon loss, it was not as effective as eliminating summer- fallow. Any cropping system that included summer-fallow lost soil carbon with time unless the system included large applications of manure. The loss of soil carbon with summer fallow can be substantial because fallowing keeps the soil moist, promoting biological oxidation, during the summer months when it would normally be dry following a crop. Crop management practices such as nitrogen fertilization increased residue production and improved carbon and nitrogen levels in soil. Soil carbon and nitrogen can be maintained or increased in these semiarid soils if they are cropped every year, and crop residues are returned to the soil.