- Nitrogen moves with mass flow of water facilitated by transpiration 

- V6 –V9 marks the corn plant’s transition into a constant rapid vegetative development and biomass gains.

- At VT-R1 (tasseling to silking), 2/3 of the total N required for corn is already accumulated in the plant.

- Successful Post N applications meet both plant nutrient uptake needs and operational efficiencies – soil N must be in solution and ready for uptake at these critical growth/demand stages- waiting too long could negatively affect both …(In 2014 some of those who waited too long missed the application window, due to wet weather).

Nitrogen in corn is arguably the most important of the essential elements known to facilitate corn growth, development and yield.  The right rate, timing and source of N supplied to corn directly affects yield and will have a significant negative impact on our environment when not managed correctly. Furthermore when N use efficiency is maximized, local profit potential is realized from increase yield and return on investment of applied N.

The V6 growth stage (6 leaf collar stage) marks the point at which corn enters a rapid phase of vegetative growth, and subsequently marks the point at which demand of resources start to become critical to physiological factors that influence yield. 

At V9 (9 leaf collars) roots initiated at nodes below and above ground are functioning to maximize water and nutrient uptake from the soil as cell division and elongation is rapid and produces a new leaf every 2-3 days. Nitrogen moves with mass flow of water, facilitated by transpiration.

From V10 – V14 both biomass accumulation and nutrient uptake is at a maximum rate and as you can see in the chart below, (Below and Bender 2010) the rate of N uptake is approximately 7 pounds per acre per day for 21 days.

At tasseling (VT), the transpiration rate of water reaches 1-2 inches per week and at 

Silking (R1), 2/3 of the total N needs for corn grain yield have been accumulated in vegetative parts of the plant to be remobilized later for grain fill. Recent research has found that nitrogen uptake in modern corn hybrids has evolved through advancements in breeding healthier plants to have a tendency for later N demand. 

R2-R6 (grain fill) approximately another 1/4 to 1/3 of the N demand should be ready for plant uptake as plant available nitrogen (PAN).

Understanding these facts related to N uptake and demand will help facilitate the 4 R’s of Proper N management leading to maximum nitrogen use efficiency, dollar return on nitrogen investment and crop yield.  The graph below depicts general N uptake and accumulation in pounds per acre at various growth stages.  The yellow box represents the portion of N in grain that is remobilized from vegetative structures, whereas the red box highlights “grain fill” N uptake from soil by plant roots. Nitrogen uptake is at a peak from V10 – V14, N should be in soil solution to insure sufficiency.

Average of 6 hybrids in Champaign and DeKalb, IL in 2010 Agron. J. 105:161-170 (2013)