59-4 Monitoring Crop Nitrogen Status in Organic Vegetable Cropping Systems.

See more from this Division: A12 Organic Management Systems (Provisional)
See more from this Session: Organic Farming Impacts: Environmental, Social, Soil Quality, Soil Management, and Cultivar Selection
Monday, November 1, 2010: 9:00 AM
Long Beach Convention Center, Room 203A, Second Floor
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Dan M. Sullivan, Oregon State University, Corvallis, OR and Nick Andrews, Oregon State University Extension Service, Aurora, OR
The applicability of traditional N monitoring approaches has not been fully demonstrated within organic vegetable cropping systems.  Over  4-yr, we monitored crop N status within on-farm and experiment station trials in western Oregon, USA.  Indicators included: preplant, in-season, and postharvest soil nitrate-N; potentially mineralizable soil N (Nmin, aerobic incubation at 22 oC), crop N uptake without current season N addition, and petiole nitrate-N.  Early-season soil nitrate tests were the simplest and most useful of the indices.  Early season soil nitrate-N values above the PSNT threshold (25 to 30 mg kg-1; 0-30 cm depth) indicated N sufficiency.  Aboveground crop N uptake on unfertilized plots on established organic farms was typically 150 to 200 kg N ha-1.   Potential Nmin (aerobic incubation) was 2 to 3x greater in soils with 5+ yr. organic history vs. soils from nearby fields under transitional or conventional management.  We recommend in-season monitoring of soil nitrate-N to adjust organic N fertility management practices to meet site-specific need.
See more from this Division: A12 Organic Management Systems (Provisional)
See more from this Session: Organic Farming Impacts: Environmental, Social, Soil Quality, Soil Management, and Cultivar Selection