Wheat-Soybean Relay Intercropping: Nitrogen Mgmt

Question: What rates of nitrogen are needed in a relay system with skipped wheat rows, and does nitrogen placement matter? How much can we reduce nitrogen inputs?

Responsible graduate student: Collin Mills (cmills24@ksu.edu)

Locations

Manhattan, Kansas

Ottawa, Kansas

Factors Evaluated

N rate: 30 lbs in fall; additional 0, 30, 60, and 90 lbs N per acre at jointing
N placement: blanket (topdressed evenly) and targeted (topdressed wheat only)

Hypothesis: A lower per-acre N rate can be applied with greater input use efficiency when targeted to wheat rows in a relay system. (at the same rate per acre, targeted applications mean wheat is given 2x fertilizer rate of blanket application - see diagram below)

Measurements

Yield (wheat and soybean)
Crop growth (soybean biomass at R2 and harvest)
Crop development (wheat and soybean stage progression, yield components)
Nitrogen fixation (nodule counts and biomass at R2, stem ureide analyses)
Soil characterization (especially nitrogen in soybean (skip rows) at relay planting)

Preliminary Results (not yet available)

2026 is the first year of this trial. Relay soybeans were May.

Funding Acknowledgement

This research is generously funded by the Kansas Soybean Commission.