Uptake of point source depleted ¹⁵N fertilizer by neighboring corn plants

Ground-based active (self-illuminating) sensors make it possible to collect canopy data that are useful for making on-the-go N fertilizer application decisions. These technologies raise questions about plant-to-plant competition for targeted fertilizer N applications. This study evaluated the extent to which fertilizer N applied to an individual corn (Zea mays L.) plant might be intercepted by adjacent plants in the row. Depleted ¹⁵N ammonium-nitrate was injected under the center maize plant while the four neighboring plants on each side in the row received the same rate as natural abundance ammonium-nitrate fertilizer. Aboveground biomass was collected 10 (at V12) and 7 (at R1) d after each fertilizer application. Plants were separated into three components at each sampling date. The uptake pattern of depleted ¹⁵N indicated an individual maize plant acquires most of its in-season N from an area within a ∼40-cm radius. Adjacent plants ∼18-cm away from the tagged-N source contained 32 to 40% of the total depleted ¹⁵N that was taken up by all nine plants in the sequence. Maize plants ~36 cm from the point source only acquired 5 to 13% of the depleted ¹⁵N source that was taken up by all nine plants. It is presently impractical to position in-season by-plant N applications beneath plants as done in this study. Surface applications of liquid N near target plants is presently possible, but the relative effectiveness would likely be less than for injection of the fertilizer beneath each plant.