Can Preplant Fertilization of Small Grains be Eliminated,
2008
M. J. Ottman
Summary
The results of this study support the practice of not applying nitrogen at
planting time even if the soil N level is low. Highest yields were obtained if the
nitrogen that would have been applied at planting time was applied at the 5-leaf
stage in addition to the N that would normally be applied at this time. If the
preplant N application is skipped, the crop nitrogen status must be monitored
carefully and N fertilizer should be applied by the 5-leaf stage to avoid a yield
reduction. If a large amount of N is applied at the 5-leaf stage, lodging may be
encouraged.
Introduction
Nitrogen fertilizer costs have increased dramatically in the past few years. In small grain production, fertilizer
represents a significant proportion of the cost of production. It may be possible to reduce fertilizer cost by skipping
the preplant application. In some cases, the soil may contain enough nitrogen so that a preplant application is not
necessary, which can be determined by a soil test. Even if a preplant soil test indicates that a preplant nitrogen
application is warranted, we know from previous research that preplant nitrogen applications are not as efficient in
getting into the plant as later applications. Preplant nitrogen applications are subject to more potential for loss due
to leaching because the root system is not established, and can also be immobilized in the soil.
Procedure
A nitrogen study with durum was established on a sandy clay loam soil at the Maricopa Agricultural Center on Field
3, Border 89. The previous crop was sudangrass. At planting time, the soil contained 4.6 ppm NO3-N and 12.3
ppm PO4-P. This amount of soil nitrate is considered low and a response to preplant nitrogen fertilizer is considered
likely. The preplant soil phosphate level was high, and therefore, no P fertilizer was applied. Kronos durum seed
was planted on January 3, 2008 at a rate of about 160 lbs seed/acre and flood irrigated on January 4. The effect of
preplant nitrogen on grain yield and protein was studied by varying the amount on nitrogen applied preplant and the
proportion of fertilizer at each application (Table 1). Flood irrigations were applied on Jan 4, Feb 26, Mar 19, Apr
3, Apr 16, Apr 25, and May 5. The experimental design was a randomized complete block with 25 fertilizer
treatments (control plus 8 N rates for each of 3 preplant N rates) and 4 replications. The plots were 10 ft x 20 ft.
Plants were sampled from a 18 inch x 14 inch (2 rows) area during the growing season on Feb 25 (5 leaf), Mar 18 (2
node), Apr 2 (boot-heading), Apr 15 (flowering), and May 13 (physiological maturity). The samples were dried in
an oven at 150 F and then weighed to determine yield. Light interception was measured within an hour of solar
noon using a Decagon Sunfleck Ceptometer on Feb 25 (5-leaf), Mar 18 (2 node), Apr 2 (boot-heading), and Apr 15
(flowering). Grain was harvested from the entire plots on June 13, but these results are not presented due to
extensive bird damage. The samples taken on May 13 were used for grain yield since bird damage occurred after
this date.
Forage and Grain Report (P-156) October 2008
7
Results and Discussion
Light interception provides an indication of plant growth, and leaf area in particular. Greater light interception is
correlated with greater leaf area. At the 5-leaf stage, light interception was not affected by nitrogen rate showing no
response to preplant nitrogen fertilizer (Table 2). At the 2-node stage, light interception was less if N was 0
preplant and only 1x at 5-leaf. By the boot-heading stage, light interception was greatest where N application was 0
preplant and 2x at 5-leaf.
Preplant N affected plant growth during the season (Table 2). At the 2-node stage, greatest plant growth was
measured where preplant N was applied. However, by the boot-heading stage, we were not able to measure
differences in plant growth whether or not preplant N was applied.
At the end of the season, skipping the preplant N application resulted in reduced plant growth if N application at the
5 leaf stage was only 1x instead of 2x. However, grain yield was not affected by preplant N application, although
grain yield was increased by the 2x N application at the 5-leaf stage (Table 3). Preplant N hastened the time to
heading and flowering by about 1 day. N application at a 2x rate at the 5-leaf stage increased lodging. Preplant N
had no affect on harvest index, test weight, HVAC, grain protein, or plant height.
The results of this study suggest that preplant N can be delayed until the 5-leaf stage without reducing yield even on
a soil low in nitrate.
Acknowledgments
Financial support for this project was received from the Arizona Grain Research and Promotion Council. The
technical assistance of Mary Comeau and Mike Sheedy is greatly appreciated.
Forage and Grain Report (P-156) October 2008
8
Table 1. Nitrogen fertilizer treatments.
N Rate (lbs N/A)
Flowering watery
kernel
(Apr 16)
Preplant
5-leaf
Total
N rate
lbs N/A
Preplant
(Jan 4)
5-leaf
(Feb 26)
2-node
(Mar 19)
Bootheading
(Apr 3)
N/A
N/A
0
0
0
0
0
0
1x
1x
50
100
150
200
250
300
350
400
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
0
2x
50
100
150
200
250
300
350
400
0
0
0
0
0
0
0
0
20
40
60
80
100
120
140
160
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
0
1x
40
80
120
160
200
240
280
320
0
0
0
0
0
0
0
0
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
Forage and Grain Report (P-156) October 2008
9
Table 2. Preplant and subsequent N application effect on light interception and total plant yield at various growth
stages.
N application
Light Interception
Total Plant Yield
Boot- FlowerBoot- FlowerTotal
5-leaf 2-node heading water
5-leaf 2-node heading water Maturity
lbs N/A ------------- % of incident ------------- ------------------------ lbs/A ------------------------
Preplant
5-leaf
0
0
0
24
53
61
58
205
1,543
2,352
4,207
5,489
1x
1x
50
100
150
200
250
300
350
400
26
34
39
38
53
39
46
29
57
73
76
78
81
79
79
76
69
80
86
84
91
90
92
91
68
80
82
83
91
88
90
88
355
429
442
274
529
492
498
274
2,875
2,340
3,348
1,904
3,896
4,393
4,144
2,751
3,547
3,696
5,526
6,671
5,750
6,148
4,543
4,070
6,770
7,542
5,912
5,501
9,496
8,924
9,135
7,816
11,027
8,276
13,416
13,304
14,138
13,292
14,400
6,808
0
2x
50
100
150
200
250
300
350
400
-----------------
63
69
77
72
75
76
86
81
75
84
92
88
91
92
97
94
70
79
92
86
90
93
94
94
-----------------
2,526
2,390
2,775
2,551
2,713
1,357
2,402
3,037
3,609
4,368
4,306
4,294
4,418
5,762
4,543
5,215
6,186
6,845
8,625
8,650
8,102
7,604
11,089
9,471
9,434
14,089
14,561
8,787
14,213
14,051
11,998
15,072
0
1x
40
80
120
160
200
240
280
320
-----------------
58
62
68
64
73
66
75
76
71
74
81
82
89
86
93
91
66
72
81
83
90
85
90
89
-----------------
2,340
2,278
1,892
2,178
2,340
1,991
2,539
1,543
3,647
5,538
4,082
4,891
5,028
4,256
5,339
5,028
8,712
6,111
8,575
8,027
8,575
7,393
8,301
6,982
9,322
10,056
9,869
9,036
13,143
9,496
12,010
12,608
NS
---
9
NS
6
NS
5
NS
NS
---
1101
+
1673
NS
2736
NS
3533
*
Avg.
Avg.
Avg.
38
-----
75
75
68
85
89
84
84
87
82
416
-----
3,206
2,469
2,138
4,994
4,564
4,726
7,637
8,322
7,835
11,833
12,776
10,692
Avg. N
--47
3
10
2
5
2
5
--50
395
25
NS
21
NS
20
1267
18
LSD.10
All N
Preplant N * Total N rate
1x
0
0
LSD.10
CV(%)
1x
2x
1x
LSD.10 = least significant difference at the 10% probability level.
NS, +, * = not significant at the 10% probability level, significant at the 10% probability level, and significant at the
5% probability level, respectively.
CV = coefficient of variation.
Forage and Grain Report (P-156) October 2008
10
Table 3. Preplant and subsequent N application effect on grain yield and various grain and plant characteristics.
N application
Preplant
5-leaf
Total
lbs N/A
Grain
yield
lbs/A
HVAC
%
Grain
protein
%
Heading
0
0
0
2,775
51
61
57
10.7
3/29
4/01
25
0
1x
1x
50
100
150
200
250
300
350
400
5,314
3,983
6,484
6,410
6,397
5,439
5,974
2,166
48
48
48
48
45
41
41
30
62
62
61
61
61
61
60
60
83
92
98
99
99
100
99
98
11.2
12.6
13.3
14.5
14.1
14.7
14.8
14.8
3/30
3/30
3/29
3/30
3/28
3/30
3/30
4/01
4/02
4/01
4/01
4/02
4/01
4/03
4/03
4/03
27
27
26
26
27
27
28
26
0
8
20
18
45
33
38
15
0
2x
50
100
150
200
250
300
350
400
4,493
6,721
7,107
4,568
6,534
6,584
5,078
6,036
48
48
49
52
46
47
42
40
62
61
61
61
61
60
60
61
82
93
99
99
98
100
98
99
11.4
12.5
14.0
15.0
14.6
15.1
14.7
14.5
3/30
3/31
3/30
3/31
3/31
4/01
3/30
4/01
4/02
4/04
4/02
4/02
4/04
4/04
4/03
4/04
27
27
27
26
26
26
27
27
0
8
53
63
45
60
68
60
0
1x
40
80
120
160
200
240
280
320
4,916
5,240
4,929
4,406
5,551
3,933
5,115
5,277
53
52
50
47
42
42
42
42
62
62
61
61
61
60
60
60
82
94
96
96
100
99
99
100
11.4
12.6
13.2
14.3
14.7
15.2
15.1
15.1
3/29
3/29
3/30
3/30
3/31
3/31
4/01
4/01
4/02
4/01
4/02
4/03
4/03
4/03
4/04
4/04
27
26
27
26
27
26
27
26
0
3
15
43
33
33
38
78
1786
*
NS
NS
1
NS
6
NS
0.7
NS
2
NS
2
NS
NS
NS
26
+
Avg.
Avg.
Avg.
5,271
5,890
4,921
44
47
46
61
61
61
96
96
96
13.7
14.0
14.0
3/30
3/31
3/30
4/02
4/03
4/03
27
27
26
22
44
30
Avg. N
642
20
NS
13
NS
1
NS
5
NS
4
1
0
1
0
NS
6
9
70
LSD.10
All N
Preplant N * Total N rate
1x
0
0
LSD.10
CV(%)
1x
2x
1x
Harvest Test
Index weight
%
lbs/bu
Flower- Plant
Height Lodging
ing
inches
%
LSD.10 = least significant difference at the 10% probability level.
NS, +, * = not significant at the 10% probability level, significant at the 10% probability level, and significant at the
5% probability level, respectively.
CV = coefficient of variation.
Forage and Grain Report (P-156) October 2008
11