traits, such as crop height, leaf area, and growth rate, vary widely among
sweet corn hybrids. Ecologist Marty Williams measures solar radiation
intercepted by different sweet corn hybrids to determine how canopy structure
affects the crops ability to compete with wild proso millet. Click
the image for more information about it.
Scientist Pinpoints When Weeds Are Most
Meddlesome By Jan
Suszkiw June 13, 2007
"Field intelligence" gathered by an Agricultural Research Service (ARS) scientist could give sweet corn growers
a new edge in their war on weeds.
Based on field studies he has conducted near Urbana, Ill., since 2004,
Williams has identified specific timeframes during the sweet corn growing
season when competition from weeds will inflict yield losses. Moreover, this
so-called critical period for weed control is influenced by the sweet corn
planting date, notes Williams, who works in ARS'
Weed Management Research Unit at Urbana.
In Illinois, one of several Corn Belt states, growers plant sweet corn
between April and early July, depending on the market they're targeting. May
and June are peak months of planting for both fresh and processing markets.
A few years ago, Williams decided to determine the critical
weed-control period and, for good measure, find out whether planting dates
affect a crops susceptibility to weeds. His experimental design called
for planting sweet corn in either early May or late June and allowing weeds to
grow to various heights (e.g., ankle, knee or shoulder high) before killing
In other plots, Williams let the weedsincluding common
lambsquarters, redroot pigweed and green foxtailgrow throughout the
corn's growing season, about 83 days. This enabled him to measure and compare
each weed treatment's effect on the crop's yield of marketable ears.
In general, the May-planted crop suffered the greatest yield
lossesup to 85 percent, versus 15 percent for June-planted corn.
Moreover, the May corn's critical weed-control period began earlier, on day 18,
when the corn had reached its four-leaf stage.
For the June-planted corn, the critical weed-control period didn't
begin until day 53, which was beyond the 12-leaf stage and only a few weeks
before harvest. Williams attributed the difference to sweet corns
excellent growth in late-season conditions, which gave the crop an edge over
For sweet corn growers in the north-central United States, planting in
June or later could mean savings on herbicides, tillage or time spent
hand-pulling weeds, such as might be practiced by organic farmers.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.