Or. Admin. R. 603-095-5065 – Soil Sampling Protocol

(1) Pre-planting soil samples or soil samples taken prior to mid- or late-season fertilizer application shall be collected at the depth of the crop root zone according to the applicable protocol in Oregon State University Extension Service Publication, A Guide to Collecting Soil Samples for Farms and Gardens (EC628) (2022) and Soil Testing Lab Selection and Recommended Analytical Methods for Oregon (EM 9423) (2024).
(2) Post-harvest soil samples shall be collected after harvest of annual crops, before three inches of rainfall accumulates, and before significant post-harvest irrigation. October 31 shall be the start date for tallying the accumulation of rainfall.
(a) Separate composite soil samples shall be collected at the 0 – 12 inch depth, the 12 – 24 inch depth and the 24 – 36 inch depth according to the protocol contained in Oregon State University Extension Publications Postharvest Soil Nitrate Testing for Manured Grass and Silage Corn (West of the Cascades)(EM 8832-E) (2021) and Soil Testing Lab Selection and Recommended Analytical Methods for Oregon (EM 9423) (2024) for post-harvest nitrate-nitrogen.
(b) If soil samples are taken after three inches of rainfall accumulates, a landowner shall collect an additional composite soil sample for the 36 – 48 inch depth to account for nitrate leaching.
(3) Soil samples shall be processed at a laboratory accredited by the North American Proficiency Testing (NAPT).

ORS 561.191 & ORS 568.900-933

ORS 568.900-933 & 468B.025(1)