Fertility and Nutrients
Side-band liquid UAN a good option
Easy to use with good seedling safety, research finds UAN is a good one-pass seeding option.
November 29, 2007 By Top Crop Manager
As farmers fine-tune their one-pass seeding and fertilization options, many
are considering whether mid-row or side-band fertilizer systems are the way
to go. While there have been studies comparing mid-row and side-band using urea
and anhydrous ammonia (NH3) with few differences in stand
establishment and yield, few studies have looked at liquid urea-ammonium nitrate
(UAN) in one-pass seeding systems. However, a recent research project sponsored
by the Indian Head Agricultural Research Foundation (IHARF) in Saskatchewan
looked at whether UAN in a one inch by one inch side-band placement had any
negative effects on stand establishment.
|Figure 1. Effects of rate of nitrogen on plant
population in spring wheat and canola in 2005. Source: Guy Lafond, Final
Report, Innovative Approaches to Land Management to Improve Nitrogen Management
at the Field Level, 2006.
"Using UAN in research plots isn't very easy, unless you have specialized
equipment, so few researchers work with UAN. We had the benefit of working in
field scale trials using commercial field scale equipment, which is a lot easier,"
explains Guy Lafond, a research scientist with Agriculture and Agri-Food Canada
at Indian Head. "In looking at the data, we were most interested in the
plant population data, and we found that essentially, the one-by-one inch placement
was safe at the rates of UAN that we used."
The UAN side-band analysis was part of the larger Precision Farming Project
sponsored by IHARF, which started in 1998. That study looked at the opportunities
to improve farming efficiencies and competitiveness with site specific management
on inputs, but in conducting the research, Lafond also found other applications
for the data.
The UAN side-banding data looked at the impact of different rates of liquid
UAN on plant densities of spring wheat and canola when using a Stealth single
side-band opener with a seed/fertilizer separation of one inch to the side and
one inch below the seed and 12 inch row spacing. A spring wheat-canola-spring
wheat-field pea rotation was used over the duration of the study. Nitrogen rates
ranged from a low of zero to a high of 100 pounds per acre.
For canola, the Canola Council of Canada recommends a target stand of seven
to 14 plants per square foot (75 to 150 plants per square metre). In wheat,
the recommended plant stand is 20 to 25 plants per square foot (200 to 250 plants
per square metre).
In the study, for all years and crops, there was no effect of nitrogen rate
on plant densities. "This would indicate that when using liquid UAN in
a side-band fashion and with a separation of one inch to the side and one inch
below the seed, there is enough separation to protect against seedling injury
from fertilizer UAN nitrogen," explains Lafond.
|UAN fits well in one-pass direct seeding operations. Photo Courtesy
Of Bruce Barker.
While Lafond's study found adequate plant stands with UAN rates as high as
100lb/ac side-banded, an earlier study by Dr. Cynthia Grant of Agriculture and
Agri-Food Canada (AAFC) shows there may be limits to the amount of UAN or urea
that can be placed in a one-by-one inch side-band while seeding canola. In unpublished
data that was presented at the Manitoba Agronomist Conference in 2004, she found
that canola stand establishment was affected by higher rates of both urea and
UAN. However, those effects could be mitigated with the use of a urease inhibitor.
In this study, though, a high seeding rate of 10lb/ac was used, which Grant
acknowledges is higher than normal and that today, their research uses normal
seeding rates of five pounds per acre. The opener ended up placing fertilizer
0.75 of an inch to the side and 1.25 inches below the seed.
Interestingly, in the AAFC Brandon study, canola plant populations were in
the seven plants per square foot range (the low end of Canola Council of Canada's
recommendations) at rates as high as 178lb/ac of urea or UAN under good seeding
conditions. Whether that is an acceptable risk would depend on a canola grower's
perspective, as well as conditions at seeding which can increase the risk of
"With the higher seeding rate, we ended up with good plant stands, even
with fertilizer damage," cautions Grant. "Today, most openers have
moved the separation a bit further away than the one-by-one inch separation
because there have been quite a few reports of damage. In Manitoba, we have
always recommended greater separation for N applications. There is a feeling
that we may have greater risk of damage because of our calcareous soils."
|Figure 2: Stand density of canola on a clay loam
soil as affected by rate and source of side-banded N fertilizer, with and
without use of urease inhibitor. Source: Grant – unpublished data;
Manitoba Agronomist Conference, 2004.
|Legend: UAN + I = UAN plus inhibitor. Urea
+ I = Urea plus inhibitor.
According to Grant's information presented at the Manitoba Agronomist Conference,
the risk factors associated with germination damage which increase the risk
of high side-band N rates "include high pH carbonated soils, soils with
low cation exchange capacity (coarse textured soils, soils with low organic
matter content), drying conditions after seeding and application on sensitive
crops, such as canola or flax. If the seed/fertilizer separation is not maintained,
risk of damage will also be higher. Seedling damage will not always translate
into a reduction in crop yield at the end of the growing season, but yield may
be reduced depending on the growing season. Seedling toxicity may delay crop
emergence and reduce crop vigour, increasing potential losses from weed competition.
Crop maturity can be delayed, leading to a greater risk of damage from fall
frosts. Crop quality may also be affected. Where risk of damage is considerable,
it may be advisable to increase the separation between the seed and fertilizer
band, use an alternate method of fertilizer application such as mid-row banding
or pre-plant banding, or use a less damaging fertilizer source."
The difficulty in assessing these risk factors is that favourable moisture
conditions may enable growers to get away with higher rates for several years,
and then a dry spring can cause a hit on seedling germination due to fertilizer
toxicity. Plus, seedling damage can be difficult to spot, unless a check strip
is left by turning off the fertilizer.
UAN side-banding systems easy to use
Many commercial and farm-built openers have been designed for one-pass seeding
and fertilizing. They range from high-tech commercial openers to simple systems
where UAN is surface dribbled from drop tubes placed on the front of the seeder
onto the soil surface more or less in line with the openers and mixed with the
soil as it falls back over the seed, and systems with separate openers for side-band
or mid-row placement.
Lafond says UAN liquid fertilizer is well suited to one-pass systems, as application
equipment for liquid is easier to work with and modify than equipment for granular
or ammonia application. Also, with liquid, the risk of granular fertilizer bouncing
into the seedrow is not a concern and the liquid tube can be directed to the
side of the side-band to further increase separation, especially when the opener
starts to wear down. "I like liquid because it is easy to use, handle and
meter and it is a lot easier to direct the liquid stream away from the seedrow,"
How liquid UAN fits into growers' seeding systems depends on the many soil,
environmental, cropping and infra-structure and logistic factors, some of which
are discussed earlier. With so many factors affecting seedling germination and
stand establishment, farmers are advised to use higher UAN rates with caution,
until they establish a comfort level under their own conditions.