Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/9/2002
Publication Date: 11/12/2002
Citation: ALBRECHT, S.L., WUEST, S.B., WILKINS, D.E. CHANGES IN SOIL CARBON IN SEMIARID DRYLAND FARMING SYSTEMS IN THE PACIFIC NORTHWEST. AGRONOMY ABSTRACTS. 2002.
Technical Abstract: In the 1930's long-term experiments were started at the Pendleton Experiment Station in northeast Oregon to evaluate the effects of fertilizer, residue management, and tillage on crop productivity in the cereal - producing, dryland regions of the Columbia basin. In this area summer moisture is too low to support warm season crops, but the region is well-suited for winter annuals and cool-season grasses. Average winter wheat yields have risen from 45 bushels/acre in the 1930's to almost 65 bushels/acre in the 1990's. However, soil organic matter continues to decline the a winter wheat-summer fallow rotation, still common in this area, even when soil erosion is minimal. Residue management practices in this region can have significant impact on soil organic matter levels. Burning of wheat stubble accelerates organic matter loss while nitrogen fertilization and the addition of pea vine reduce the decline. Manure applications are also capable of preventing organic matter decline and may actually increase soil carbon. The loss of soil organic matter appears to be substantially less with annual cropping than in a cereal-fallow rotation. Stubble mulching and direct seeding, both of which leave residue on the soil surface to deter erosion, support organic matter retention. Soil under 60 years of stubble mulch now has about one-third more organic matter in the top three inches than soil that was mold-board plowed.