Top Crop Manager

Features Agronomy Fertility and Nutrients
Achieving success with variable rate fertilization

Close co-operation between agronomist and grower is essential!

November 26, 2007
By Top Crop Manager


Spatial variation in soil characteristics, topography and soil-stored moisture
are a few of the features of the prairie region that have an impact on the yield
potential of a given landscape segment. The demand for N by crops and the ability
of the various soil segments to supply N is also naturally expected to vary
across the landscape.

For these reasons, it is logical to assume that landscape-based, variable rate
application of N fertilizer would be more profitable than a uniform application
across all of the landscape segments. However, the variable fertilizer application
rate concept has been slow to develop and, in fact, some attempts had proven
to be failures. Therefore, until recently, putting this concept into practice
has proven to be somewhat elusive.

Wade Barnes spends a lot of time at his computer developing soil
test supported zone maps that enable growers to accomplish variable rate
fertilizer applications. He was named the 2005 prairie region 'CCA of the
Year' for the leadership he has shown in making variable rate fertilization

This landscape-based approach to fertilizer application seemed to make sense
to Wally Orr who farms in the Crystal City region of Manitoba. In order to be
able to vary the rate of fertilizer in his fields at the time of seeding, it
would require considerable modification of his Great Plains no-till drill. In
addition to incurring these costs, it would be necessary to install a Raven
rate control meter for his mid-row NH3 coulters, as well
as a Zynx multi-tasking control unit, all of which adds up to a considerable

Wally farms with his cousin Ken Orr, his uncle Tom Orr and his father, Harold
Orr. Together, they operate a 2000 acre grain farm, a cow-calf operation as
well as a feedlot. While Wally was convinced that variable rate fertilization
made sense, but because of the costs involved, his partners were less certain.

To help sell this concept to his partners, Wally enlisted the support of Wade
Barnes, a Certified Crop Adviser (CCA) who had started providing landscape-based
fertilizer recommendations in the Pilot Mound region. Barnes had worked as a
retail agronomist for eight years before becoming an independent crop advisor.

Together with Curtis MacKinnon and Kory Vandamme, Barnes now operates Farmer's
Edge Precision Consulting Incorporated, which specializes in developing variable
rate application maps for fertilizer. Their goal is to develop stable, long-term
relationships with their clients by providing top-notch, fertilizer application
maps that are based on good agronomic information and improve the grower's profitability.
"I want to build strong, partner-based relationships with my growers that
will last for many years. I have no interest in providing an agronomic service
that is terminated after only two or three years," claims Barnes.

To initiate the process of developing variable rate application (VRA) maps,
or as preferred by Barnes, zone maps, they will utilize whatever information
is available to them. This includes satellite imagery, detailed soil maps, elevation
maps, electrical conductivity maps and yield maps. However, the most important
information involves working with the grower to capture his knowledge of field
history, as well as yield variability. Barnes indicates that, "In terms
of crop production agronomics, Wally is one of the most sound growers I have
ever worked with," so his input into developing the zone maps was very

Wally Orr confesses that it was not without some fear and trepidation that
he embarked into variable rate fertilization, but he is now a very strong believer
in this concept. So strong, that he is now planning to add another tank to his
drill in order to achieve greater flexibility in varying K and S applications.
He claims that, "These were the most uniform crops that I have ever harvested
and there was zero lodging." He attributes past problems to uniform application
of fertilizer across all parts of the field, which resulted in a considerable
amount of under and over-fertilization in his fields.

As a result of zone-based soil testing, rates of N were reduced, while P and
K rates were increased in the lower-lying areas where lodging had formerly been
a serious problem. Fertilizer was also cutback on the knolls where yield potential
was lower. Wally indicates that, "Under the former approach, plants grown
on the mid-slope positions were being starved for N. This is the area where
we increased N application."

An example of zone maps that were developed for one of Wally Orr's
fields. This field contained seven different management zones and the top
Nitrogen Rx, or application map, was developed based on the soil test nitrogen
information contained in the lower map. The maps also contain a printout
of the total number of acres contained within each management zone.

Barnes indicates that the fertilizer recommendations for the various map zones
are based on soil test recommendations that were derived from the zero to six
inch and six to 24 inch soil samples collected from each zone. He indicates
that some groups offer VRA maps that are not backed-up with soil testing and
he feels this approach is inadequate. "Soil testing gives us a great deal
of confidence in the fertilizer recommendations that are provided by the labs.
For canola, the recommended N rate can change from zero to 180lb/ac and S can
vary from zero to 40lb/ac within a field. In the case of P2O5
and K2O, rates can vary from five to 45lb/ac and zero
to 60lb/ac, respectively. There is no way I could recommend that great a difference
in nutrient application rates within the same field without the support of soil
testing," he says.

Barnes has been a leader in introducing variable rate fertilization practices
in southern Manitoba. Wally says, "Wade and Curtis MacKinnon are the best
agronomists that I have ever dealt with. I am extremely pleased with the agronomic
services that Wade has provided to our farming operation." Barnes indicates
that a typical field can be divided into four to seven management zones. On
average, soil samples are collected for every five acres of field area and every
sampling site is geo-referenced.

Curtis Cavers, a land resource specialist with Manitoba Agriculture, Food and
Rural Initiatives, speaks highly of the type of agronomic services provided
by Barnes: "Wade has been very proactive in trying to understand potential
impact of landscape features on fertilizer recommendations. He checks detailed
survey reports where available and will seek clarification from our soil specialists.
Coupled with the producer's knowledge about a field, Wade divides the field
into management zones for strategic soil sampling, fertilizer application and
other management practices."

Many of the growers that Barnes had serviced in the past, asked him for information
about the potential for using variable rate fertilization on their farms. John
Lee of Agvise helped provide Barnes with information about the zone management
approach being used in North Dakota. As well, he provided contact information
for crop consultants that were utilizing this concept south of the border. Lee
states that, "Wade uses good science to break fields into several management
zones, and the soil test results provide the good science used in developing
the fertilizer recommendations for each of these zones."

Certified crop advisers across Ontario
assist growers with crop management decisions. Since 1996 individuals from most
growing regions in Ontario have entered this intensive program. They maintain
their designation with continuing education credits by attending courses and
workshops. Look for the CCA emblem!