WEST LAFAYETTE, Ind. — A historical analysis of corn
research shows that new hybrids are taking up more nitrogen than older plant
varieties after the crucial flowering stage, a clue as to how plant scientists
will need to adapt plants to increase yields.
Tony Vyn, a professor of agronomy, and Ignacio Ciampitti, a
postdoctoral research associate, are studying the timing of nutrient uptake in
corn and how that process affects yield. They found that modern hybrids took up
27 percent more total nitrogen from the soil after flowering than pre-1990 corn
In fact, nitrogen uptake after flowering in post-1990
hybrids averaged 56 percent of the total grain nitrogen at the end of the
Primarily, more grain nitrogen came from new nitrogen uptake
from soil during grain filling, as opposed to nitrogen being remobilized from
plant leaves and stems. The higher amount and duration of nitrogen uptake
contributed to superior grain yields even as actual grain nitrogen
The timing of nitrogen uptake also is important in
understanding how other plant nutrients are affected. Vyn said optimum nitrogen
levels increased plants’ abilities to absorb phosphorus, potassium and sulfur.
Part of the corn plant’s response to receiving adequate
nitrogen is that progressively higher percentages of total plant phosphorus,
potassium and sulfur end up in the grain fraction at harvest.
“You need to think in terms of nutrient balance. If you have
a plant with more biomass and more yield, it will be taking up more nutrients in
a balanced manner that shifts with plant needs and growth stages,” Ciampitti
Post-1990 corn hybrids use nitrogen more efficiently, so
less is necessary per unit of yield. But as those plants increase nitrogen
utilization, they increase their uptake of other nutrients, which affects how
much of those nutrients growers need to use and when they need to apply
“At some point, they’ll need to increase the amount of these
other nutrients applied to their fields as yields continue to increase,” Vyn
He and Ciampitti also found that the timing of nutrient
uptake is important for predicting yield and nutrient efficiencies.
Vyn said it would be economically beneficial to identify
simple, early-stage plant traits that could be measured to predict final yield,
but the earliest they could predict yield with even 50 percent certainty was at
flowering, much later than hoped.
“It’s desirable to estimate yield and nutrient efficiency of
new genotypes at an early stage, but you have to wait until flowering time,” he
“You need to wait until flowering stage for most of the
total potassium uptake to be present in the plant and recognize that
proportionally more phosphorus than nitrogen uptake can occur later in modern
corn hybrids. But all nutrient uptake rates are dependent on the specific
interactions of hybrids with their environment and management factors like plant
density and soil nutrient availability.”
Ciampitti said biomass and nutrients were measured for two
weeks before, at and two weeks after, flowering in an effort to predict yield.
Those periods were crucial because it is the time in which most corn biomass is
made in modern hybrids when water is not limiting.
The results of the studies were reported in two journal
articles. The review of nitrogen source changes was published in Crop Science. Nutrient accumulation and
partitioning results were published in Agronomy Journal.