Download Optimizing Crop N Use Efficiency Using a Variable Source N

Optimizing Crop N Use Efficiency Using a Variable Source N Fertilizer Application Strategy
Adam J. Noellsch1, Peter P. Motavalli1, Kelly Nelson2, Newell Kitchen3, Stephen H. Anderson1, Peter Scharf4, and Paul Tracy5
1Dept. of Soil, Environmental and Atmospheric Sciences, University of Missouri, Columbia, MO 65211,
2Greenley Research Center, Univ. of Missouri, Novelty, MO 63460, 3USDA-ARS, Univ. of Missouri, Columbia, MO 65211,
4Division of Plant Sciences, University of Missouri, Columbia, MO 65211, 5MFA Incorporated, Columbia, MO 65201
Materials and Methods
Abstract
Development of improved management practices to increase nitrogen use
efficiency (NUE) within agricultural fields is needed to improve crop production
and reduce nitrogen (N) loss. Field studies planted to corn (Zea mays L.) were
conducted in 2005 and 2006 in the claypan region of north central (Centralia) and
northeast Missouri (Greenley Research Center) to determine the effects of
landscape position and soil depth to the claypan on crop growth and N uptake,
and to examine the use of a variable-source N fertilizer application strategy to
optimize crop N fertilizer use. Treatments at the northeast Missouri site consisted
of a control and 168 kg N ha-1 of urea, polymer-coated urea (PCU), a 50%
urea/50% PCU mixture, or anhydrous ammonia applied in 457 m long strips that
included variation in elevation and claypan depth. At the north Centralia site, N
fertilizer treatments of 168 kg N ha-1 of urea or PCU were broadcast surfaceapplied within three different cropping/tillage systems and at different landscape
positions representing the summit, sideslope and footslope positions in the field.
At the Greenley site, PCU treatments showed a consistent 1535 to 1814 kg ha-1
increase in corn grain yields compared to the urea treatments in 2005 and 2006,
respectively, in the low lying area, possibly due to the wetter conditions in the
low-lying area affecting the fate of the applied N. Similarly, anhydrous ammonia
application resulted in a 1475 and 1659 kg ha-1 yield increase in 2005 and 2006,
respectively, in the low-lying area. At the north central Missouri site in 2006, the
corn grain yield of the PCU-treated area was 1203 kg ha-1 higher than that of the
urea-treated area only at the footslope landscape position in the no-till
corn/soybean/wheat cropping system. These results suggest that a variable
source N fertilizer application approach based on identifying periodically wet
field areas due to their lower elevation may improve NUE and economic returns.
Introduction
Reduced NUE and crop yields due to landscape variability may warrant the
use of variable source N (VSN) fertilizer applications. The VSN fertilizer
application strategy is when enhanced efficiency N fertilizers are applied in field
areas that have a higher risk for N loss and conventional N fertilizer sources are
applied in lower risk areas of that same field, possibly through use of a multi-bin
fertilizer spreader.
Schmidt et al. (2007) showed that economically optimal N rate (EONR) may be
affected by within-field soil water content variability during a growing season.
Gravimetric moisture content data collected at the Greenley Memorial Research
Center in the claypan region of northeast Missouri has shown that soil water
content can increase by as much as 22% after a rainfall event from a summit to
footslope position with only 1 m difference in elevation (unpublished data). Use
of enhanced efficiency fertilizers in low-lying landscape positions may be an
effective way of improving NUE.
Objectives
1. To determine the interactive effects of landscape position and soil
depth to the claypan on NUE and agronomic response of corn to
conventional and N fertilizer sources.
2. To examine the use of a variable-source strategy to optimize N
fertilizer use efficiency and increase economic returns.
A two-year field trial planted to corn (Zea mays. L) was initiated in 2005 at the
Greenley Experiment Station in Northeast Missouri in the central claypan area
(Fig. 1A) on a Putnam silt loam soil (fine, smectitic, mesic, Vertic Albaqualfs).
The site was mapped for elevation with a total station and apparent electrical
conductivity (ECa) using a EM-38 sensor (Fig. 1B). Measurement of soil ECa gives
an indication of relative depth to the claypan subsoil layer. The experimental
arrangement was a RCB design with 4 reps and treatments consisting of a
control and 4 N treatments (168 Kg N ha-1) applied across 3 landscape positions
(summit, sideslope and low-lying).
1A.
• The treatments included:
1.
2.
3.
4.
Anhydrous ammonia
Conventional urea
Polymer coated urea (ESN)
Mixture of 50% PCU/50%
urea
5. Control with no N
Figures 2 A & B.
(A) Topsoil
depth at the
Centralia site as
derived from
ECa data
collected with
an EM-38
sensor. (B) Map
showing
elevation and
general
landscape
positions of
2006 & 2007
plots at
Centralia.
Table 3. Corn grain yield, N uptake and NUE in 2006 and 2007 at the Centralia site.
2B.
Topsoil Depth at the
Centralia Site
A. 2006
B. 2007
Cropping
System
Landscape
Position
N
treatment
1
Min. Till
Summit
Control
Urea
PCU
DMRT(0.05)*
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Sideslope
Footslope
Topsoil Depth (cm)
0 to 10
10 to 14
14 to 17
17 to 20
20 to 24
24 to 28
28 to 35
35 to 140
2
No-Till
Corn/Soy
Summit
Sideslope
Footslope
Results and Discussion
• All N treatments were pre-plant broadcast-applied
and incorporated immediately after application.
• The low-lying area in the experimental field
frequently had standing water during the
growing season (Fig. 1C).
1B.
• Both silage and grain yields were
determined and the tissue N content
of the silage was used to calculate N
uptake and N use efficiency (NUE).
3
No-Till
Corn/Soy/Wheat
Table 1. Initial soil characteristics at the Centralia site.
Landscape
Position
Bulk
Density
-3
Summit
1
Min. Till
(Shallow)
2
No-Till
Corn/Soy
3
No-Till
Corn/Soy/Wheat
Sideslope
(Deep)
Low-lying
M g m -3
-- % --
1.28
1.22
1.29
0.02
1.33
1.25
1.41
0.09
1.36
1.36
1.40
NS
1.90
2.10
2.03
NS
2.10
2.30
1.93
NS
2.30
3.07
2.20
0.62
pH(s)
NO3-N
NH4-N
Exchangeable
Bray I
P
Soil Test
K
Ca
Mg
-1
--------------------------------------------- mg kg-1 ------------------------------6.33
6.30
6.87
NS
5.70
5.97
6.53
0.72
5.80
5.80
6.23
0.31
3.63
11.36
18.06
NS
12.06
10.09
3.43
NS
6.25
13.10
11.19
NS
6.70
9.04
6.80
NS
11.99
7.48
7.78
NS
9.85
9.63
9.00
NS
18.2
32.5
34.0
NS
26.0
29.2
19.9
NS
23.4
24.4
22.7
NS
137
207
156
NS
126
236
157
106
150
223
151
26
2239
2947
2712
702
2152
3212
2407
880
2297
3159
2397
328
Footslope
CEC
-1
cmolc kg-1
241
432
265
NS
282
530
235
284
282
562
258
96
15
21
16
NS
17
25
15
NS
17
25
18
2
Table 2. Corn grain yield, N uptake and NUE in 2005 and 2006 at Greenley.
Control
Urea
PCU
PCU/Urea
Anhydrous
DMRT(0.05)
2005 Grain Yield
Summit
Sideslope
Low-lying
DMRT(0.05)*
-1
-------------------------------- kg ha ---------------------------4614
4537
4457
NS
5866
4960
5818
NS
5898
4637
7353
1920
5965
4840
6538
NS
6312
5561
7293
1567
599
NS
1345
N treatment
Control
Urea
PCU
PCU/Urea
Anhydrous
DMRT(0.05)
N uptake
-1
Control
Urea
PCU
PCU/Urea
Anhydrous
DMRT(0.05)
-------------------------------- kg ha ---------------------------45
45
43
NS
72
62
74
NS
71
54
110
26
69
63
95
NS
83
69
121
NS
12
13
32
•
•
NUE
---------------------------------- % -------------------------------Control
----Urea
17
10
19
NS
PCU
16
6
41
17
PCU/Urea
15
11
32
12
Anhydrous
23
15
47
20
DMRT(0.05)
6
8
23
*Duncan’s Multiple Range Test (P < 0.05); NS = not significant
•
N uptake
•
-1
Control
Urea
PCU
PCU/Urea
Anhydrous
DMRT(0.05)
NUE
Control
Urea
PCU
PCU/Urea
Anhydrous
DMRT(0.05)
•
2006 Grain Yield
Summit Sideslope
Low-lying
DMRT(0.05)
-1
----------------------------- kg ha -------------------------6091
5776
8116
2006
11949
11048
11038
NS
12506
11744
12852
NS
12624
11937
11860
NS
12663
11679
12697
NS
1087
870
1150
--------------------------- kg ha-1 ---------------------------44
55
53
NS
152
158
122
NS
131
138
133
NS
161
165
128
NS
148
177
127
45
12
13
58
------------------------------- % ----------------------------------64
58
41
NS
52
49
48
NS
69
65
45
NS
62
73
44
NS
6
8
NS
Grain
N
Yield
uptake
-1
---------- kg ha -------4130
4357
4943
NS
2943
3073
4065
NS
4178
6081
6227
NS
2845
6520
5577
2321
1627
5877
3691
3525
3870
8942
10462
3463
4503
6910
6699
2112
4731
6861
6373
1523
6471
7073
8276
958
44
89
82
27
42
63
90
NS
60
96
105
NS
34
87
127
47
39
77
57
36
45
132
116
62
49
77
107
23
41
88
85
35
67
134
96
51
NUE
-%-27
23
NS
-18
29
NS
-21
27
NS
-32
56
24
-23
11
NS
-52
42
NS
-17
34
18
-27
26
NS
-39
17
NS
Cropping
System
N
treatment
Grain
Yield
-1
kg ha
1
Min. Till
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
Control
Urea
PCU
DMRT(0.05)
6560
5512
5048
NS
4146
6121
6658
NS
5146
6609
5756
NS
3821
5577
5333
1295
3301
5121
4894
1667
4016
5333
6113
1383
2666
4715
5089
1785
3122
4764
5333
1985
3414
6081
6390
2552
2
No-Till
Corn/Soy
3
No-Till
Corn/Soy/Wheat
*Duncan’s Multiple Range Test (P < 0.05); NS = not significant
*Duncan’s Multiple Range Test (P <0.05); NS = not significant.
N treatment
Figures 1 A-C. (A) Location of the
Greenley and Centralia sites in the
Central Claypan area. (B) ECa map
produced with data collected from
the Greenley site using an EM-38
sensor. (C) Photo taken at the
Greenley site from the sideslope
position, showing the low-lying area
the day after a rainfall event.
Summit
Sideslope
Low-lying
DMRT(0.05)*
Summit
Sideslope
Low-lying
DMRT(0.05)
Summit
Sideslope
Low-lying
DMRT(0.05)
Organic
Matter
Summit
Sideslope
Inorganic N
Cropping
System
1C.
The Centralia site in north central Missouri
was established in 2006 on a long-term (15
yrs) cropping system experiment with
claypan soils. Treatments were arranged in a
RCB with 3 reps and consisted of a control
and post-plant application of 168 kg N ha-1 of
either urea or PCU applied across 3
landscape positions (summit, sideslope,
footslope) and 3 cropping systems : (1)
minimum till, corn/ soybean rotation, (2) notill corn/soybean, (3) no-till
corn/soybean/wheat.
2A.
•
As a result of long-term cropping, initial soil properties at Centralia varied by
cropping system and landscape position in respect to bulk density, organic
matter content, pH, soil test K, and exchangeable Ca and Mg (Table 1).
At the Greenley site, PCU treatments showed a consistent 1505 to 1818 kg
ha-1 increase in corn grain yields compared to the urea treatments in 2005
and 2006, respectively, in the low lying area, possibly due to the wetter
conditions in the low-lying area affecting the fate of the applied N (Table 2).
Similarly, anhydrous ammonia application resulted in a 1505 and 1630 kg ha-1
yield increase in 2005 and 2006, respectively, in the low-lying area.
Significantly higher grain yields due to N fertilizer treatments were observed
at Centralia in 2006 and 2007 in CS# 2 & 3, but PCU had higher grain yields
compared to urea only in 2006 in CS# 3 at the footslope position.
Both N uptake and NUE at Greenley were higher at the low-lying position
compared to urea when PCU and anhydrous were applied in 2005, but this
result was not repeated in 2006.
In 2006, N uptake was generally higher in the summit and footslope position
in CS # 2 & 3 and no consistent differences were observed in N uptake or
NUE among the N fertilizer treatments.
Using results from Greenley and based on a corn grain price of $0.12 kg-1 and
a total application cost of $50 ha-1, the profit from using PCU versus urea in
the low-lying area was $175 ha-1.
Conclusion
• Application of multiple N fertilizer sources in fields with claypan soils and
low-lying areas may enhance crop yields and increase economic benefits
compared to a single application of urea fertilizer across the whole field.