A practical guide to pulling clean, consistent sap samples for corn, soybeans, and wheat—so the data you get back actually reflects what's happening in your fields.
Sap analysis tells you what's actually moving through the plant right now—nutrients, deficiencies, imbalances—before stress shows up on the leaves or the yield monitor.
But the lab can only work with what shows up at the door. A sample pulled at the wrong time of day, from the wrong row, or stored warm will tell a story your fields aren't actually telling. The steps below come from years of pulling samples ourselves—follow them and your data will be sharp enough to make decisions on.
Mornings before 11 a.m. and under 80 °F—the leaves still have tension and moisture. Skip rain and extreme weather days. Sample 3+ days after any fertilizer or pesticide pass.
Stay off the outer rows and the first 20 feet of every row—edge effects skew results. Pull from the sunny side of plants with average leaf quality. Sample abnormal areas separately, never blended in.
Pat leaves dry if wet—moisture skews results. Bag NEW and OLD leaves separately and label clearly. Never mix varieties in the same bag—genetic differences alone will throw the numbers off.
Collect 80+ grams each of NEW and OLD leaves—160+ grams total per sample set—bagged separately. Cut sequential leaves into thirds and submit only the middle 4–5 inch section.
V2–V4. Sample the entire young plant (without roots) and place it in a single zip-lock bag.
V6–8, V10–12, R1–2. Pull NEW and OLD leaves separately. Once ear development starts, consider adding the ear leaf or replacing NEW with the ear leaf.
NEW — youngest fully formed leaf, 2nd–3rd from the top.
OLD — healthy lower leaf, 2nd–4th from the base.
EAR — collard leaf supporting the ear (R-stage option).
Collect 80+ grams each of NEW and OLD trifoliate leaves plus the petiole—160+ grams total per set, bagged separately.
V2 — first trifoliate. Collect NEW fully developed trifoliate leaves with petiole. Bag and label NEW.
Every 2+ weeks. Through V4–V12, R1 (beginning bloom), R2 (full bloom), R3 (beginning pod), R4 (pod fill), and pre-harvest—NEW and OLD as a set.
NEW — youngest fully expanded trifoliate + petiole.
OLD — oldest still-viable trifoliate + petiole.
Pull from the sunny side of the plant.
Collect 80+ grams each of NEW and OLD leaves—160+ grams total per set. Cut blades approximately 2 inches from the base.
Feekes 2–3 (Tillering). NEW fully developed leaves only. Cut blades ~2 in. from the base. Bag and label NEW.
Feekes 4–5 (Jointing). NEW + OLD leaf set. Stack each in a separate, labeled zip-lock bag.
Feekes 7–9 (Flag Leaf). NEW + OLD leaf set, same procedure. Sample from the sunny side; avoid head-tissue contamination on the blades.
What you do between pulling the sample and getting it to the lab matters as much as the pull itself. Heat, moisture, and time will all change what shows up on the report.
In the field: drop samples straight into a cooler with ice packs—no direct contact with the ice. Pat leaves dry if they're wet. Let the air out of bags before you seal them.
Before you ship: double-check that NEW and OLD bags are labeled clearly and kept separate. Note any recent fertilizer or irrigation timing on the bag—the lab uses that context. Never bag two varieties together.
Shipping: overnight or 2-day on Monday, Tuesday, or Wednesday for morning arrival. Friday and weekend shipments sit warm and skew the data.
Calibrated Agronomy dealers can print sample labels and route shipments directly inside CalibratedIQ.
Find a dealer near you →Pulling a clean sample is half the work. If you want a second set of eyes on your sampling plan, or a kit to get started, our agronomists are a phone call away.