Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/9/1995
Publication Date: N/A
Technical Abstract: Six long-term experiments (LTEs) presently exist at Pendleton. The primary Pendleton LTE consists of a wheat/fallow residue management study started in 1931. Other Pendleton LTEs include a wheat/fallow tillage- fertility (1940), a wheat/pea tillage (1963), a wheat/fallow no-till (1982), and grass pasture and cereal monoculture (1931) studies. Soil C and N levels in all LTEs are sensitive to level of residue input, intensity of tillage, and frequency of cropping. Changes in C and N in the upper 30 cm of soil in the residue management experiment are nearly linear over time, with only generous manure application able to prevent a decline in soil organic matter. The rate of C loss over time correlates highly with the level of C input from crop residue and organic amendments. Stubble-mulch tillage increases soil C and N content about 10%. Annual- cropping maintains soil C and N above levels for wheat/fallow rotation. Inorganic N fertilization increases soil C and N retention primarily through greater production of crop residue.