Introduction

Implementing appropriate N management practices such as the 4 R Nutrient Stewardship principles can minimize N loss, optimize N uptake, maximize productivity and improve farm profitability. Right timing of N application is one of the practices of the 4 R nutrient stewardship principles. The ultimate goal of timing is to supply adequate amounts to synchronize with the most active period of N uptake to minimize losses. Thus, a major focus is to avoid over or under applications which can reduce profits and harm the environment.

Nitrogen uptake throughout the growing season follows a sigmoid shape (Figure 1). Prior to V6 growth stage, the corn plants take up less than 12% of the total N during the growing season. Approximately, 60% of the total N uptake occurs between V6 to VT growth stage. About one-fourth of the plant N uptake is after tasseling. Considering there is limited N uptake prior to V8, sidedress N fertilizer application is recommended between V4 to V6 growth stage to reduce risk for N loss or delayed N applications.

In Tennessee, the current recommendation is to split apply one-third at planting (shortly after emergence) and then sidedress the remaining N for dryland corn production. Since the update of the current recommendations for N management in dryland corn, there have been newer corn hybrids and N management tools such as enhanced efficiency fertilizers. To address these new developments, trials were conducted to examine 1) the optimal recommended rate to split-apply N, 2) proportions of N to split-apply, and 3) sidedress timing of N applications. This publication provides findings of these trials.