Benefits
of Exactrix® Superior Application Uniformity vs. Conventional
Ammonia and Granular Fertilizer Application Systems
Bert Bock
Senior Advisor to Exactrix Staff and a
former TVA scientist involved in development of commercial
fertilizers .
One of the
hallmarks of Exactrix systems is application uniformity for
anhydrous ammonia and liquid fertilizers.
That includes application uniformity among openers and along
each opener path. For
anhydrous ammonia, this two-way uniformity is achieved by
maintaining the ammonia as a high-pressure liquid rather than a
mixture liquid and gas both in the manifold and in the distribution
lines between the manifold and openers.
Medium pressure is used to achieve uniform application of
liquid fertilizers. With
Exactrix systems, anhydrous ammonia application rates for individual
openers vary on average 1 to 3 percent from the average application
rate for all openers (Figure 1).
This is referred to as the coefficient of variation (CV).
This is far superior to traditional anhydrous ammonia
application systems which often have CVs from opener-to-opener in
the 20% range or higher and provide a pulsating
(sinusoidal)
application rate along opener paths as illustrated in Figure 2.
Exactrix systems are also superior to granular fertilizer
systems (spinner and pneumatic) that often have CVs in the 20% range
or higher, especially with higher application rates and wider
application widths (1, 2, 3, 4).
Uniformity of granule application is affected by many
factors, including particle size, field slope, and field roughness
over which the operator has little control.
These factors don’t affect uniformity of application with
Exactrix systems.
Non-uniform
application not only causes some plants to be over-fertilized and
some plants to be under-fertilized.
The over-fertilized hot spots are more susceptible to gaseous
ammonia moving to the soil surface and being lost to the atmosphere.
Over-fertilized hot spots can also prevent timely access of
plant roots to nutrients in the bands and can increase the
probability of seedling damage.
What
does this large Exactrix application uniformity advantage mean
relative to yield when growers are striving to maximize fertilizer
use efficiency? The
inference from the study summarized below is that Exactrix
application uniformity can provide a yield advantage of several
bushels per acre compared with application uniformity provided by
conventional anhydrous ammonia and granular fertilizer systems.
This is in addition to improvements in yield and
fertilizer use efficiency related to co-injection of N, P, K, and S
vs. surface application, especially in no-till systems
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There are
few studies that have measured effects of fertilizer
application uniformity or non-uniformity on yields in the
field. Some
theoretical studies show little effect of non-uniform
fertilizer application on yields but more credible
evidence is provided from actual measurements in the
field. Kansas
State University conducted a field study comparing corn
yield with two anhydrous ammonia application systems, one
with a CV of 19% and one with a CV of
9% as determined in a stationary test (5).
Test results from the stationary systems with
ammonia captured in water cans are presented in Table 1.
The stationary system with a 19% CV used a
commercial variable diameter orifice (VDO) controller and
the stationary system with 9% CV used a prototype pulse
width modulation (PWM) controller.
In addition to giving less uniformity of
distribution among openers, the VDO controller
under-applied ammonia on average (22.3 vs. 27.0 lb ammonia
per opener during the stationary test.
This was corrected for the plot studies.
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In a
field trial, plots 8 rows wide and 400 ft. long were
established with no N applied and with 120 lb N/Ac applied
at V8 stage using the DVO and PWM controllers.
Soil ammonium N + nitrate N levels were measured
soon after application at four 30-foot intervals along
each opener path. Grain
yield was also measured based on three mature plants
collected near each soil sampling site.
Soil
ammonium N + nitrate N levels are presented in Table 2.
The CV for soil ammonium N + nitrate N from the VDO
controller was 55.6% vs. 16.8% from the PWM controller and
the ranges were 22 to 216 ppm from the VDO controller and
61 to 140 ppm from the PWM controller.
This is much greater variability than measured in
the stationary applicator tests.
This likely is due partly to greater application
variability with a mobile applicator and partly to
variability in soil N levels.
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Grain
yield was not nearly as variable as the soil ammonium N +
nitrate N levels (Table 3).
This is likely due to roots from individual plants
exploring a large enough area to take up N from soil
supplying differing amounts of N and providing some
averaging across soil N levels.
Even so, the yield CV was 17.2% for the DVO
controller and 12.2 % for the PWM controller.
The yield range was 102 to 186 bu/Ac for the DVO
controller and 120 to188 bu/Ac for the PWM controller.
More importantly, the average yield based on the
three plant samples near each soil sample location was
149.4 bu/Ac for the DVO controller and 154.5 bu/Ac for the
PWM controller.
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In
another field trial, ear leaf N at silking and grain
yields were determined based on whole-plot measurements
(Table 4). Treatments
included no applied N, and N applied with VDO and PWM
controllers at 60 and 120 lb N/Ac.
At the 120 lb N/Ac rate, grain yield with the PWM
controller was 9 bu/Ac higher than with the VDO
controller. At
the 120 lb N/Ac rate, ear leaf N was 0.38 percentage
points higher with the PWM controller than the DVO
controller. There
was clearly significantly more N available to plants with
the PWM controller than the DVO controller.
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What do
these results imply for yield benefits from Exactrix
application uniformity?
Keep in mind that conventional anhydrous ammonia
and granular fertilizer application systems have CVs of
around 20% or higher and are expected to perform roughly
the same or worse than the DVO controller in terms of
uniformity of application.
Alternatively, Exactrix systems have CVs between 1
and 3% and are expected to perform better than the PMW
controller in the study summarized above.
Furthermore, Exactrix systems are not adversely
affected by changes in factors such as environmental
conditions, field slope, field roughness, and granule
properties. Therefore,
the yield advantage from Exactrix application uniformity
is projected to be greater than the yield difference for
the two ammonia systems in the study summarized above.
The inference from the study summarized above is
that when producers are striving to maximize fertilizer
use efficiency, Exactrix application uniformity can
provide a yield advantage of several bushels per acre
compared with application uniformity provided by
conventional anhydrous ammonia and granular fertilizer
systems.
Don’t
forget to add application uniformity to your list Exactrix
benefits when calculating your bottom line.
Plant roots and nitrogen mobility can provide some
“averaging” to partially compensate for non-uniformity
of fertilizer application; however, Exactrix systems can
provide significant yield increases related to better
application uniformity than provided with conventional
anhydrous ammonia and granular fertilizer application
systems. This
is in addition to improvements in yield and fertilizer use
efficiency related to co-injection of N, P, K, and S vs.
surface application, especially in no-till systems.
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