Monitoring Soil Nitrate to Estimate Cover Crop Nitrogen Contribution in Organic Vegetable Production Fields

Authors: Nick Andrews, Dan M. Sullivan, and Kristin Pool, Oregon State University

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Organic vegetable growers rely on legume cover crops as an economical source of plant-available¬† N. This research evaluated N contributions to summer vegetable crops by cover crops (CC)¬† residues by monitoring soil nitrate (NO3-N) concentrations during the summer crop growing season. Replicated field plots were established with three CC mixes: solo common vetch (V),¬† phacelia + V (PV), and cereal rye + V (RV), plus a winter fallow (F) control in grower fields in the north Willamette Valley OR. Soil textures were … Read the rest

Soil Nitrate Testing for Willamette Valley Vegetable Production (2019) EM9221

Link: https://catalog.extension.oregonstate.edu/em9221

This publication describes how to use in-season soil nitrate testing to adjust sidedress N fertilizer application rate to match crop N requirements. Data to support our recommendations comes from field trials conducted in the Willamette Valley for vegetable crops produced during summer months.… Read the rest

Estimating Plant-Available Nitrogen Release from Cover Crops

This publication assists western Oregon farmers and agricultural professionals in determining the nitrogen fertilizer replacement value of winter cover crops. Includes information on plant-available nitrogen (PAN) basics; a site-specific, step-by-step method to estimate PAN; Willamette Valley case studies; and appendices summarizing Willamette Valley cover crop research that supports these PAN estimates.

Link: https://catalog.extension.oregonstate.edu/pnw636

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Baseline Soil Nitrogen Mineralization: Measurement and Interpretation (2020) EM9281

This Extension publication reviews baseline N mineralization which refers to plant-available nitrogen release that accompanies the decomposition of soil organic matter. The rate of baseline soil N mineralization is governed by the quantity and quality of soil organic matter, as modified by soil moisture and temperature. Baseline soil N mineralization typically supplies about half of crop N uptake. Soils that have been heavily manured for many years or are naturally very high in soil organic matter can supply most of the N required for crop production. Several laboratory tests for N mineralization are available, but most are useful only as … Read the rest