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was established in 1931 at the Oregon State University’s Columbia Basin Agricultural
Research Center near Pendleton, OR. The on-going experiment evaluates residue
and N treatments that included no N addition with fall burning (FB0), spring burn-
ing (SB0), and no burning (NB0), 45 kg N ha−^1 with SB (SB45) and NB (NB45),
90 kg N ha−^1 with SB (SB90) and NB (NB90), manure (MN, 5.32 Mg dry mass ha−^1
year−^1 ), and pea vines (PV, 0.99 Mg dry mass ha−^1 year−^1 ) under a WF system receiv-
ing 405 mm of mean annual precipitation. A nearby grassland (GP) was used as a
reference. After 80 years of experimentation all WF treatments lost SOC compared
to the grassland (Fig. 4 ). The MN and PV treatments maintained higher SOC stocks
than other treatments. All burn treatments had lower SOC stocks than corresponding
no-burn treatments. The lowest SOC stocks were observed under treatments where
residues were burned in the fall soon after harvest. Wheat – summer fallow systems
have lost more than 60 % of the original SOC (Machado 2011 ; Ghimire et al. 2015 ).
Using the same data set, Machado ( 2011 ) observed that 30 years (1976–2005) of fall
burning of wheat residue depleted about 17.3 % SOC (0.34 Mg SOC ha−^1 year−^1 ) in
the top 60 cm soil and the depletion of SOC was significantly higher than a reduc-
tion of 10.4–11.9 % SOC (0.22–0.28 Mg SOC ha−^1 year−^1 ) with no residue burning
treatments. A similar experiment at the same location also revealed lower SOC and
N with fall burning (9.9 g C kg−^1 and 0.73 g N kg−^1 ) of wheat residues compared to
spring burning (11.4 g C kg−^1 and 0.88 g N kg−^1 ) and no-burning (10.9 g C kg−^1 and
Fig. 4 Soil organic carbon (SOC) and nitrogen (TN) stock (0–60 cm) after 80 years (1931–2010)
of different crop residue and nitrogen management treatments in a conventionally tilled (plow) WF
system and undisturbed grassland at the Columbia Basin Agricultural Research Center (CBARC)
near Pendleton, OR. FB fall burn, SB spring burn, NB no burn, MN manure application, PV pea
vine, and GP undisturbed grassland. 0, 45, 90 accompanied with FB, SB, and NB indicate amount
of N (kg ha−^1 ) applied from chemical fertilizer (Source: Ghimire et al. ( 2015 ))
N.C. Hansen et al.