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Nitrogen Product Comparison
Aim
This trial is investigating the uptake by wheat of different Nitrogen fertilisers.
Summary
Four nitrogen fertiliser products were compared for efficacy in relation to providing the crop with
sufficient N to optimize production at two sites, Birchip and Marnoo. The products compared
were: granular Urea, granular Calcium Ammonium Nitrate (CAN), liquid Urea Ammonium
Nitrate (UAN) and liquid Urea. The products were applied three times (pre-sowing; at the five
leaf stage and at the end of tillering).
The Birchip site was not responsive to N and no differences were observed. At Marnoo there was
a 0.4t/ha benefit in applying N fertiliser compared to the control of no N. The largest yield
response to N was found at the late application (end of tillering). There were no differences
found in the products used, even though at the five leaf application timing the conditions were
conducive to volatilisation.
Background
Plants use inorganic nitrogen (nitrate) for growth. Organic nitrogen, or applied nitrogen, must be
converted to inorganic nitrogen before it can be used by the plant. This conversion is called
mineralisation and is carried out by soil micro-organisms. The time taken for this to happen
depends on soil conditions, with the dominant factors being soil moisture and soil temperature.
Up to 1kg/ha/day of nitrogen is mineralised in moist, warm topsoil in spring, while only
0.2kg/ha/day mineralises in a moist, cold soil in winter.
Four different products were investigated:
Urea contains 46% N. Urea is still the cheapest form of nitrogen at the present time, however it
is susceptible to volatilisation on alkaline soils.
CAN (Calcium Ammonium Nitrate) contains 27% N. Half of the applied nitrogen exists as
ammonium the other exists as nitrate (plant available form). Due to the percentage already
existing as nitrate the chance of volatilisation is reduced.
UAN (Urea Ammonium Nitrate) a liquid which contains 32% N w/w (42%N w/v) - 16% as
urea, 8% as nitrate and 8% as ammonium. UAN is taken up by the crop through its leaves
however a proportion of N is still taken up through the roots and therefore requires rainfall for
movement into the soil.
Liquid Urea is granular urea converted into a liquid through mixing with water and pumping a
large amount of air through it (in order to reduce crystallization). It is relatively cheap and
convenient. Liquid urea has some leaf uptake and still requires rainfall for plant uptake through
the roots.
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Methods
Replicates:
4
Plot Size:
3m x 25m
Variety:
Yitpi
Sowing Date:
Marnoo June 9; Birchip June 25 2005
Seeding Density:
175pl/m2
Fertiliser:
Granulock 10Z 50kg/ha
Herbicide:
MCPA500 (300ml) + Lontrel (100ml), Atlantis (300ml) + Hasten (1%).
Trials were carried out at Birchip and Marnoo. Treatments are outlined in Table 1.
Table 1: N fertiliser treatments, rates and timings
Treatment
Application Method
Rate /ha
Timing
Granular Urea
Pre-drilled
60kg
Pre-sow
Calcium Ammonium Nitrate
Pre-drilled
81kg
Pre-sow
UAN
IBS
65L
Pre-sow
Liquid Urea
IBS
60kg
Pre-sow
Granular Urea
Spread
60kg
GS15
Calicum Ammonium Nitrate
Spread
81kg
GS15
UAN
Flat Fan
65L
GS15
Liquid Urea
Flan Fan
60kg
GS15
Granular Urea
Spread
60kg
GS30
Calcium Ammonium Nitrate
Spread
81kg
GS30
UAN
Flat Fan
65L
GS30
Liquid Urea
Flat Fan
60
GS30
Control
Results
Unfortunately during August and September, the critical months for nitrogen application, rainfall
was below average and unpredictable. Tables 2, 3, 4 & 5 show the rainfall as well as maximum
and minimum temperatures collected from the Birchip and Marnoo sites for the 10 days
immediately after nitrogen application.
Dates of spreading at Birchip were on 2/9/2005 and 20/9/2005. Dates of spreading at Marnoo
were on 3/8/2005 and 29/8/2005
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Table 2: 10 day weather observations after 1st nitrogen application (2/9/05) at Birchip
2/9
3/9
4/9
5/9
6/9
7/9
8/9
10/9
11/9
12/9
13/9
Rain mm
1
-
-
1
-
-
-
3
-
-
-
Max temp
16.5
12.5
17
18
19
22
25
25
16.5
13
14.5
Min temp
3.5
6.5
6.5
2.5
2
6
11
13
9.5
3.5
3
Table 3: 10 day weather observations after 2nd nitrogen application (20/9/05) at Birchip
20/9
21/9
22/9
23/9
24/9
25/9
26/9
27/9
28/9
29/9
30/9
Rain mm
0.5
-
-
-
-
0.5
-
-
10
1
-
Max temp
16.5
22.5
19
18.5
17.5
16
21
21
19
17.5
22.5
Min temp
4.5
4.5
9.5
9.5
10.5
9
10.5
2
8.5
6.5
6
Table 4: 10 day weather observation after 1st nitrogen application (3/8/05) at Marnoo
3/8
4/8
5/8
6/8
7/8
8/8
9/8
10/8
11/8
12/8
13/8
Rain mm
1
0.5
-
-
-
-
0.8
4
-
-
-
Max temp
22.3
13
13.9
15.3
15.3
16
14.1
9
12.2
12.5
15.5
Min temp
8.3
4.2
-0.9
2.7
2.1
0
5.2
0
0.8
-0.4
3.7
Table 5: 10 day weather observation after 2nd nitrogen application (29/8/05) at Marnoo
29/8
30/8
31/8
1/9
2/9
3/9
4/9
5/9
6/9
7/9
8/9
Rain mm
-
14
1
-
-
-
-
3
-
-
-
Max temp
24
16.5
12.5
12.5
15.7
12.8
16.1
16.8
18.6
21.4
24.5
Min temp
11.4
11.1
5.6
-1.9
2.7
5.7
4.7
1.2
3.5
8
11.5
At Birchip, rainfall was well below average for the month of September 25.5mm (50 year Sept
average is 42mm). Only 3mm fell for the first 10 days after the application of nitrogen at the 5leaf stage (GS15 application). For the second nitrogen application the only substantial rainfall
event (10mm) came eight days after application.
At Marnoo, there was no rain event greater than 1mm for seven days after the application of
nitrogen at the five leaf stage (GS15 application). During this time there was one warm day – on
the day of application, the other days were quite cool. These conditions would have been
conducive to volatilisation of urea (a little bit of moisture and mild conditions). At the second
application at the end of tillering (GS30) there was a significant rainfall event the day following
application of the N products – perfect for ensuring that all N products were washed into the soil
and protected from volatilisation.
Dry matter cuts at Marnoo were taken 7 and 26 days after the application of the N fertilisers at the
five leaf stage (GS15 application). The dry matters were analysed for N content, so that N uptake
in the foliage could be assessed. There was no difference in dry matter (t/ha) taken from the 1st
cut, however differences in dry matter were observed after the 2nd cut (Table 6). There was also
a significant difference in the level of conversion of kilograms of applied nitrogen as N uptake by
the plant in kg per hectare.
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The topdressed urea treatment and the control had significant lower dry matter cuts and kg N/ha
in the foliage when compared to the treatments which had nitrogen applied as CAN, UAN or
liquid Urea.
Table 6: Dry Matter and N uptake at the Marnoo site
1st cut 10/8/2005
Timing
Control – no N
2nd cut 29/8/2005
Dry Matter
t/ha
N Uptake
kg N/ha
Dry Matter
t/ha
N Uptake
kg N/ha
1.6
92
2.6
113
Urea
Pre-drill
1.8
110
3.5
164
Urea
GS15
1.5
82
2.5
108
CAN
GS15
1.5
90
4.3
188
UAN
GS15
1.7
99
4.2
174
Liquid Urea
GS15
1.5
89
3.5
145
NS
P<0.001
24
5
P<0.001
1.4
5
P<0.001
12
3
Significant diff:
LSD0.05
CV%
8.1
Yield
At the Birchip site there was no significant difference in grain yield between the control (2.5t/ha)
where no nitrogen was applied and those plots treated with nitrogen.
At the Marnoo site, there was a significant difference in yield between the control (3.7t/ha) and
those plots treated with nitrogen fertiliser (average 4.2t/ha). There was no difference between the
pre-sowing treatments and the early application (GS15), however when N was applied at GS30
the yields were significantly higher (4.1, 4.0 and 4.3 t/ha respectively as an average of N product)
(Table 7). No differences in yield were observed between the four products.
Table 7: Crop yield at Birchip and Marnoo as a response to different N fertiliser products and time of
application
Birchip
Marnoo
Application time
IBS
GS15
GS30
IBS
GS15
GS30
Granular Urea
2.6
2.3
2.4
4.2
3.9
4.3
CAN
2.2
2.2
2.5
4.1
4.1
4.2
UAN
2.7
2.5
2.1
4.2
4.0
4.3
Liquid Urea
2.2
2.4
2.5
4.0
4.1
4.2
Signficant diff:
Product
Timing
LSD0.05
CV%
NS
NS
5.4
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NS
P<0.01
0.25
2.8
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Protein
At Birchip and Marnoo there was no significant difference in protein between the control (no
nitrogen) and those plots treated with nitrogen fertiliser. There were no differences in protein
response to applying different N fertiliser products (Table 8).
Table 8: Protein at Birchip and Marnoo as a response to different N fertiliser products and time of
application
Birchip
Marnoo
Application time
IBS
GS15
GS30
IBS
GS15
GS30
Granular Urea
14.6
15.2
15.1
10.1
9.8
10.3
CAN
15.1
15.1
15.0
10.2
10.0
10.4
UAN
14.7
15.1
15.1
9.6
9.9
9.9
Liquid Urea
15.4
14.7
14.6
10.2
10.1
9.9
Signficant diff:
Product
Timing
CV%
NS
NS
1.5
NS
NS
0.8
Screenings
At the Birchip site there was no significant difference in screenings between the control (4.2%)
and those plots treated with nitrogen.
At the Marnoo site there were significant differences in screenings between the control (6.6%)
and those plots treated with nitrogen. The differences were greater between the control and when
nitrogen was applied at the later growth stages (screenings were lower at the later growth stages)
(Table 9).
Table 9: Screenings at Birchip and Marnoo as a response to different N fertiliser products and time of
application
Birchip
Marnoo
Application time
IBS
GS15
GS30
IBS
GS15
GS30
Granular Urea
3.7
3.0
3.5
4.2
4.4
2.3
CAN
3.6
4.1
3.4
5.3
2.3
2.6
UAN
4.3
3.2
4.4
6.8
2.9
2.2
Liquid Urea
3.6
3.8
4.8
5.1
2.7
2.3
Signficant diff:
Product
Timing
LSD0.05
CV%
NS
NS
2.8
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NS
P<0.01
0.4
11.1
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Interpretation
The critical spring months of August and September, when nitrogen was applied, were dry in
2005. In some cases, paddocks were only four days away from running out of moisture.
In the ten days after the treatments were applied there was only one rainfall event greater than the
critical 8-10mm required for nitrogen to move down the profile. This event (14mm) occurred at
the Marnoo site on the 30th of August.
The Birchip site was high in soil N and this site did not benefit from additional N fertiliser.
Marnoo did respond to additional fertiliser because the soil was much lower in available N at
sowing and conditions were more conducive to growth. A difference in N uptake at Marnoo was
recorded at the 1st application timing (GS15) in the amount of N uptake in the crop – the granular
Urea was not taken up into the crop at the same rate as the other products primarily because there
had been no rain for seven days after application. However, this did not translate into a yield
difference.
There was a significant yet small increase in yield observed at the Marnoo site, when nitrogen
was applied at GS30. This may be attributed to the 14mm rainfall event which occurred two days
after application, resulting in greater nitrogen uptake. These results are similar to the work
undertaken by Nick Poole in the canopy management trial at Lubeck (and reported in this
manual) where a significant yield benefit was found when applying N late (GS31) compared to
pre-drilling or at GS15.
The only other difference observed were the higher screenings at the Marnoo site for those plots
treated with nitrogen at sowing. In this situation there has been a miss-match between the timing
of nitrogen versus when it was required. This lead to the plant having an over supply of nitrogen
at a time when moisture was lacking, resulting in the plant haying off and producing a smaller
grain sample.
Commercial Practice
If rainfall can be reliably predicted, urea is still the most cost effective product:
Cost (as of Sept 2005 – time when products were used)
Urea $480/t @ 46%N or $1.05/kg N
CAN $480/t @ 27%N or $1.77/kg N
UAN $506/B-double @ 42%N(w/v) or $1.20/kg N
The benefit of other nitrogen products, such as UAN or liquid urea, is in the potential to reduce
the number of machinery operations. By tank mixing herbicide/fungicide products with UAN,
and covering two operations in one pass, fuel and labour costs can be reduced.
BCG CROP AND PASTURE PRODUCTION MANUAL 2005-2006