Features Agronomy Irrigation
140 bushels per acre of irrigated soft white wheat!

As market prices decline, and the demand for soft white spring wheat wavers
in the face of the low-carb diet, returns to farmers have also declined for
CWSWS. Still, new advances in soft white wheat production can gross as high
as $715 per acre and help compensate for negative market pressures.

"If you look at average yields of irrigated soft white spring wheat, the
returns might not look that good compared to other crops," says Andy Kovacs,
executive director with the Alberta Soft Wheat Producers Commission at Lethbridge,
Alberta. "But if you start pushing yields up to the full potential, soft
white spring wheat still looks very good."

Average yields have hovered around 72 bushels per acre in recent years. But
Kovacs says top growers routinely hit 110 to 130 bushels per acre, and some
growers have managed to pull off 140 bushel per acre crops.

Dr. Sadash Sadasivaiah discussing his research program.

New varieties breaking yield barriers
Soft white spring wheat varieties have come a long way since 1975 when there
was only one variety registered. Called Fielder, the variety had many negative
attributes such as poor disease resistance, sprouting and weak straw. The 1991
introduction of AC Reed brought better disease resistance, along with better
resistance to shattering, lodging and sprouting. Soft white spring wheat breeder,
Dr. Sadash Sadasivaiah* with Agriculture
and Agri-Food Canada (AAFC) at Lethbridge, said that in the first year of introduction,
AC Reed captured 90 percent of the soft white spring wheat production.

Since 1991, five other soft white spring wheat varieties have been registered.
The most recent, and exciting, is AC Andrew, which brings 18 percent higher
yield than AC Reed. AC Andrew is a semi-dwarf variety, and Sadasivaiah said
it occupied a large acreage in 2003 and 2004.

Market acceptance is growing for AC Andrew and most millers have switched a
portion of purchases over to it. Similar to the process that maltsters must
use when changing malt barley varieties, millers must work with their customers
to ensure the new variety meets end-use criteria. AC Andrew is acceptable to
both domestic and export cookie and pastry markets, but is not suitable for
the soup thickener market.

Different millers have different requirements, and growers should contact them
to find out which varieties make good choices. Soft white spring wheat for export
is still marketed through the Canadian Wheat Board.

Sadasivaiah recently obtained registration on a sixth cultivar, Bhishaj. It
is a semi-dwarf with a better disease package than AC Andrew, although lower
yield potential. Still, Bhishaj has yielded nine percent higher than AC Reed.
The AAFC breeding program continues to evaluate new varieties, and Sadasivaiah
hopes to have another variety or two up for registration evaluation in 2006.

Irrigation management key to high yields
In 2004, soil research scientist Dr. Ross McKenzie with Alberta Agriculture,
Food and Rural Development (AAFRD) initiated a three year agronomic study on
soft white spring wheat production. He says that many of the old recommendations
are based on the variety Fielder, (it is no longer licensed) which had lower
yield potential than most of today's varieties. He hopes to be able to refine
the recommendations, especially in the areas of seeding date, plant populations
and fertility requirements.

However, McKenzie says one of the most limiting factors overlooked by farmers
is irrigation management. A good crop of soft white spring wheat will use about
18 inches of water through the growing season, depending on conditions. Where
difficulties usually arise is during periods of high water use over the four
week period between heading out and filling.

"It is easy to fall behind after the crop has headed out. The crop uses
about two inches of moisture per week at that stage and at peak moisture requirements,
most pivots can't keep up to crop demand if the weather is hot and there is
no rain," explains McKenzie.

A pivot can typically put on three-quarters to one inch of water at a time,
and takes about four days to work a circle. That means it would take about eight
to nine days to put on two inches of water, short of crop requirements. The
trick is to ensure that the soil moisture is near field capacity as the crop
enters the high-use period.

Many of the heavier soils under irrigation at Lethbridge have the potential
to store 2.5 inches of moisture per foot of soil, at field capacity. Soft white
spring wheat roots concentrate in the top 18 inches of soil, but will extract
water to 36 inches. As a result, farmers can count on utilizing stored soil
moisture in the top three feet. It is very important that soil moisture not
fall below 50 percent field capacity.

"When a clay loam soil is near field capacity, it has about three to 3.25
inches of stored water that a crop can readily use," says McKenzie. He
says that by having the soil near field capacity going into the critical heading
and filling period, the crop will not run out of water during irrigation despite
the fact that a pivot might not be able to keep up with demand.

Another caution is to dig down to see where soil moisture ends. Often, the
top of the soil is moist but from 18 to 36 inches down, the soil is not near
field capacity. By monitoring the entire rooting profile, irrigation can be
better managed. "A $50 soil auger is a very important piece of irrigation
equipment. It lets you quickly find out how much water is stored in the soil
profile," says McKenzie.

When to turn off the pivot is another good question. McKenzie feels that once
the crop reaches the milk stage in the seed, "it is best to have three
inches of stored soil water to work with to complete filling." He says
that, depending on the soil moisture and growing conditions, another one inch
of irrigation might be warranted.

Match fertility with target crop yields
With higher target yields, in the 120 to 140 bushels per acre range, McKenzie
is interested in seeing if nutrient recommendations have changed for the new
soft white spring wheat varieties. His research is looking at rates of up to
160 pounds per acre of nitrogen (N), along with a look at the response to phosphorus
and potassium.

In the research, McKenzie hopes to find out nitrogen response, and the effect
on yield and protein content. Current N recommendations call for up to 170 to
180 pounds per acre of soil plus fertilizer N for a targetted yield of 100 bushels
per acre. Soil test levels are based on soil nitrate-N tests taken from a two-foot
core sample.

For phosphate, McKenzie says fertilizer recommendations should be based on
soil tests. Using current recommendations, he says that if soil test P is in
the 70 to 80 pound per acre range, phosphate fertilizer is not recommended.
With soil test P levels of around 50 pounds, McKenzie recommends a maintenance
application of 25 to 30 pounds per acre P205,
although a yield response may not be noticed. If the soil test P level is lower
than 20 to 30 pounds per acre, 35 to 45 pounds of P205 per acre will usually
show a good response.

Over the years, McKenzie has not seen a response to potassium or sulphur fertilizers
on most irrigated soils in southern Alberta. Micronutrient fertilizer is not
part of his research trials. He says that most southern Alberta soils are not
deficient in micronutrients, and that they should only be considered after consulting
a crop specialist or CCA agronomist.

Whether soft white spring wheat figures into 2005 cropping plans obviously
depends on grain price predictions for the 2006/07 crop year. However, Kovacs
says that growers should crunch the numbers based on achieving higher yields
and returns than has typically be done in the past. "If you are hitting
140 bushels per acre, the numbers start to look very favourable."

Dr. Sadash Sadasivaiah passed away during 2005. His soft wheat
breeding research is continuing under the guidance of Dr. Rob Graff, the
winter wheat breeder at the AAFC Lethbridge Research Centre.