Nitrogen deficiency and corn yield with delayed N application

Abstract

AbstractDelaying the application of N to corn (Zea mays L.) may help to match N supply to N uptake, but may also increase the risk of yield loss if N is applied too late or N uptake is delayed. In a 3‐yr study with corn following soybean [Glycine max (L.) Merr.] (SC) and corn following corn (CC), N application was either split, with half (112 kg N ha–1) at planting and the rest at stages ranging from V3 to R3; or with the entire increment (224 kg N ha–1) applied at these stages. In SC, there was no yield loss from delaying application of the second increment of N to as late as R3, but yields declined as the full increment of N was delayed, by 5% at V9 to 34% at R3. In CC, delaying the second N increment to stage R2 or R3 lowered yield by 5% compared to application at V3, and delaying the full increment of N increasingly lowered yield, by 8% at V6 to 40% at R3. Corn able to recover leaf chlorophyll content (SPAD) following delayed N application produced full yields, and cumulative N deficiency (CND, ΔSPAD × delay expressed as modified growing degree days over periods with ΔSPAD>0, SPAD‐MGGD) was linearly correlated with yield loss. With half of the N at planting, the remainder could be delayed to R1 or later without yield loss, but without N at planting, N needed to be applied before stage V9 in SC and before stage V6 in CC in order to assure maximum yield.