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ARS Home » Pacific West Area » Pendleton, Oregon » Columbia Plateau Conservation Research Center » Research » Publications at this Location » Publication #83307
Title: LONG-TERM RESIDUE MANAGEMENT EXPERIMENT:PENDLETON, OREGON

Author
item Rasmussen, Paul
item SMILEY, R - OREGON STATE UNIVERSITY
item Albrecht, Stephan

Submitted to: North Atlantic Treaty Organization Advanced Study Institute Series
Publication Type: Book / Chapter
Publication Acceptance Date: 8/8/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: We are using increasing amounts of nitrogen (N) fertilizer for crop production in the United States. This necessitates that we must more precisely estimate N provided by the soil to prevent under- or over- fertilization and their inherent adverse effects on plant nutrition and environmental quality. Long-term changes in N mineralized by soil may also identify trends in soil quality and provide an assessment of the sustainability of agricultural practices. We collected surface soil from treatments in five long-term (30-60 yr old) experiments to determine the effect of crop rotation, tillage, fertilizer, and residue management on mineralizable N. We compared estimates of N mineralized both in the laboratory and under field conditions. Soil N mineralization from cultivated soil was only 32-51% of that mineralized from pasture soil. Past fertilizer-N application increased the organic N content of soil and mineralized proportionately more N in the field. Nitrogen produced during aerobic incubation also increased with increasing N application, but not in the same pattern as that in field studies. Soil disturbance during collection and processing appears to alter N release patterns and precludes its use to estimate N mineralization potential. About 10% more N was mineralized from soil in conservation tillage than from soil that was plowed.

Technical Abstract: Increasing N fertilizer use in crop production necessitates more precise estimates of N provided by the soil to prevent under-or over- fertilization and their inherent adverse effects on plant nutrition and environmental quality. Long-term changes in N mineralization may also identify trends in soil quality and provide an assessment of the sustainability of agricultural practices. We collected samples from the 0-20 cm soil zone of treatments in five long-term (30-60 yr old) experiments to determine the effect of crop rotation, tillage, fertilizer, and residue management on N mineralization and compare N release under field conditions with that during aerobic incubation. Laboratory samples were incubated in glass bottles at 25 ºC and -0.02 MPa for 0, 7, 14, 28, and 49 d. Soil N mineralization from wheat (Triticum aestivum L.)/summerfallow, wheat/pea, and wheat/wheat crop rotations were 32, 42, and 51% of that mineralized from non-cultivated pasture soil. Increasing amounts of N fertilizer applied increased organic C and N in soil and mineralized proportionately more N during a 14-month fallow. Nitrate-N produced during aerobic incubation also increased with increasing N application, but the regression slope was not the same as that for N accumulation in the field. Soil disturbance during sample collection and processing apparently alters N release and precludes its use to estimate N mineralization potential. Conservation tilled soils mineralized about 10% more N than moldboard plowed soil. The percentage of N mineralized increased with increasing organic N content of soil, suggesting that organic N attained through favorable crop management practices is more labile than native N in the soil matrix.