Earshoot N Dynamics during the Critical Period for Maize.

Previous research has suggested that earshoot N content is associated with final kernel number - and, therefore, yield - in maize. It has also been demonstrated that N taken up at the onset of reproductive stages, and throughout grain-filling, is highly partitioned to the developing ear. Ensuring sufficient available N in the root zone at the onset of the critical period has the potential to increase the earshoot N content and thereby also improve final grain yield.  Preliminary N rate/timing studies involving detailed analyses of earshoot and earleaf N concentrations over time in modern hybrids and hybrids released 20 years ago provide insights into the relationships among earshoot N content and kernel number, kernel weight, and final grain yield. The sensitivity of detecting N stress in maize during the critical period (2 weeks before and after anthesis) varies between earshoots and earleaves. It is apparent that the use of either earshoot or earleaf N as a predictor of current plant N status and future grain yield is dependent on both genotype and time of sampling.