Submitted to: World Congress of Soil Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/31/2002
Publication Date: 7/31/2002
Citation: GRIFFITH, S.M., NELSON, M.A., OWEN, J.S. N PROCESSING IN GRASS SEED CROPS DIFFERING IN SOIL DRAINAGE AND DISTURBANCEIN WESTERN OREGON, USA. WORLD CONGRESS OF SOIL SCIENCE. 2002. Abstract p. 1627. Interpretive Summary:
Technical Abstract: Recent listings of Willamette River runs of chinook salmon under the Endangered Species Act and the need to prepare watershed-scale water quality management plans have focused considerable attention on the impact of agricultural practices on environmental quality in the Willamette Valley, Oregon. Since perennial grasses grown for seed comprise 55% of the Valley's land-use, a better understanding of fertilizer use by crops and the N cycle as a whole, would lead to improving crop fertility practices and preserving ground and surface water quality. The objectives of were: 1) to determine the effects of tillage on mineralization and nitrification processes and the factors (e.g., soil moisture and temperature) that regulate these processes at three different Willamette Valley sites contrasting in soil drainage class and grass species grown for seed; and 2) to relate crop above and below ground biomass accumulation and N uptake to soil mineralized and fertilizer available N. These data were compared with temporal soil N and mineralization process data to determine relationships between soil N availability and plant uptake throughout the season. Findings have shown that net N mineralization and immobilization were greater for the well- drained soil with the fine fescue seed crop compared to the moderately drained soil with the tall fescue seed crop. Conventional tillage resulted in greater N mineralization and immobilization in the fall and spring compared to no till treatment.