Features Agronomy Corn
Warm season crops assessed for winter swath grazing

Before European settlement, the native tall grass prairie in central Manitoba
was dominated by Big Bluestem, a warm season grass. Logically, then, growers
and researchers have wondered if warm season forage crops might be better adapted
to greenfeed, silaging or swath grazing in Saskatchewan.

"Warm season crops with longer maturity tend to have greater yield potential,"
says Lorne Klein, a forage specialist with Saskatchewan Agriculture and Food
(SAF) at Weyburn. "If you have enough heat units, that only makes sense."

Golden German millet. Seeded June 10. Picture: September 5, 87 days. Photo Courtesy Of Lorne Klein, SAF.

Klein was part of a three year trial comparing warm and cool annual crops at
Agri-Arm research sites across Saskatchewan. The trial looked at two seeding
dates, eleven crops and two harvest times. The research provides further guidelines
on what crops to grow for greenfeed, silage and winter swath grazing.

"The main point I make to producers is that if you are going to grow a
crop for hay or silage, then stick with oats and barley," explains Klein.
"Seed them early because the long-term averages tell us that the best yields
for cool season crops are when they are seeded early."

Swath grazing changes everything

However, if a producer is growing a forage crop for swath grazing, oats and
barley do not have as good a fit, for several reasons. For swath grazing oats
and barley, the crops generally must be swathed 70 days after planting. So when
they are planted in late May, they must be swathed sometime in late July or
early August, resulting in serious quality loss between swathing and grazing
in November or December. The other reason is that as cool season crops like
oats and barley are planted later, the yield potential drops off rapidly.

"The rule of thumb is that for every week you delay seeding a cool season
crop after May 25, you lose 10 percent in yield. If you seed on June 10, you
give up 20 percent in yield," explains Klein.

Warm season crops, though, can have an ideal fit for swath grazing. Seeding
of warm season crops must be delayed until early June when the soil has warmed
to a minimum daily soil temperature of 10 degrees C. But with later maturity,
they can be swathed in September just prior to or immediately after the first
killing frost.

To investigate the potential of warm season annual crops, the SAF trials looked
at several different species, including millets, sorghum-sudangrass and corn.
Klein says the swath grazing yield results have been variable, depending on
environmental conditions, crop and location.

In 2002 and 2003, the trials at Redvers, Indian Head and Canora showed that
Golden German millet had a significant yield advantage over oats and barley.
These Saskatchewan sites are geographically closest to the native tall grass
prairie of the Red River Valley. However, in 2004, the millets did not grow
very well due to cool growing conditions.

At Scott, Saskatchewan, the millets struggled and produced low biomass. For
areas in the western parts of Saskatchewan, the production from warm season
crops was less dependable.

Klein selected the warm season crops based on seed availability and relative
cost of production. He found a seed supplier in Texas who was able to provide
advice on which warm season crops were commonly available.

Looking at cost of production, Klein says the crops in the trials, excluding
corn, cost about the same to grow as an oats or barley crop. However, with today's
low barley and oats seed prices and the slight increase in the cost of millet
seed, the warm season crops now cost a bit more to grow.

Typically, the crops were seeded at recommended rates, with 50 pounds per acre
of nitrogen and 20 pounds per acre of phosphorus side-banded at seeding. A high
input corn trial was also included with an additional nitrogen application of
120 pounds per acre, and a double wide seedrow spacing.

The crops were established with direct seeding equipment into standing stubble
at most locations. In most cases, uniform and vigorous emergence was obtained
from the foxtail and proso millet varieties, even when seeded in the middle
of May. When soils were cold, Klein says emergence of the warm season crops
was delayed and weeds became a larger problem. Consistent and even emergence
from the sorghum-sudangrass and pearl millet varieties was difficult to achieve.
These two crops need special care and attention during establishment. Corn emergence
was consistent and fairly even.

"It takes a different agronomic package to be successful. You need to
understand that and know what you are getting into," says Klein. "Warm
season crops are very non-competitive until they hit about six weeks."

Klein explains that a cool season crop has the ability to grow through cool
temperatures, continuing cell division and elongation. Conversely, a warm season
crop emerges, grows to about four inches tall, and then sits there as cell division
occurs. Then, once the plant reaches a certain stage, the cells elongate. "A
warm season plant reaches a certain stage and then just explodes in growth."

Low crop residue conditions also favour warm season crops since the soil warms
faster. Heavy residue is tougher on warm season crops with cool soils and more
reflective sunlight off the stubble. "You need the summer heat to get a
warm season crop yielding well."

Crops seeded in mid June required fewer days to head than those seeded in mid
May. Of the warm season crops, crown millet was the earliest to head at 50 to
60 days. Siberian Red millet headed at about 65 to 70 days. Golden German and
White Wonder millet headed around 75 to 90 days. Strain R German, pearl millet
and sorghum-sudangrass were the latest to head at about 80 to 95 days. The variety
of corn used reached blacklayer or physiological maturity in 2003 but not 2004.
All millets were very slow to emerge from the soil under cool conditions making
them vulnerable to weed pressure especially from wild oats.

"You have to understand that the millets have different days to maturity
and select the right one for swath grazing," says Klein.

Because of later maturity and tolerance to warmer temperatures, the warm season
crops remained green and continued to grow late in the season. Swathing in early
to mid September, just prior to a killing frost, maximized the yield. There
is little risk of weathering in the windrow since day length is short with cool
temperatures.

Klein says that when the yield results are averaged over all locations, they
indicate that Golden German millet is very competitive in the production of
biomass. The results from corn indicate that it can produce large amounts of
biomass but is even more sensitive to the environment than Golden German millet,
with variable yields from year to year.

Forage values analyzed

Forage samples for each crop were also submitted for analysis. Golden German
millet and crown millet had protein levels that were similar to oats and barley.
The protein requirements for beef cows, basis dry matter, are seven percent
in second trimester, eight to nine percent in third trimester and 10 to 11 percent
post calving. Corn tended to be marginal for protein content in some years and
may need to be supplemented as cows approach calving.

Looking at Total Digestible Nutrients (TDN), the later maturing crops did not
lose TDN between swathing and sampling in December. Earlier maturing crops like
oats, barley and crown millet had significant declines in TDN after swathing.

In eastern Saskatchewan, Klein says that later maturing millets such as Golden
German, Strain R German and White Wonder appear to be suited for swath grazing.
However, future seed supplies of Strain R German millet and White Wonder will
most likely not be available, leaving Golden German as the millet of choice.

"Golden German millet is well adapted for swath grazing on the eastern
side of Saskatchewan. More data is required to determine its adaptability in
central and western Saskatchewan," says Klein. -30-