Oakes
Corn Response to Fertilizer N Rate in
Ten Farm Fields, 2006
Corn Response to Fertilizer N Rate in
Six Farm Fields, 2007:
Corn N Rate Studies in Producer Fields
Corn Response to Fertilizer N Rate in
Ten Farm Fields, 2006: The
effect of fertilizer nitrogen‑rate on yield and plant-soil nitrogen relationships
was studied in ten irrigated corn fields (fields a-j), on five farms at
Oakes ND, in 2006. Historically, low
fertilizer nitrogen prices and less precise methods of fertilizer application
resulted in higher than required applications of N to manage risk. With current technology and soaring nitrogen
prices this strategy in no longer relevant.
In this study producers applied 50 lb/acre less N than the field rate in
a strip across their field and in a second strip applied 50 lb N/acre more than
the field rate. These strips and the
field rate were than compared by yield, soil nitrate-N content (spring and
fall), end of season nitrate-N stalk test, grain protein, starch and oil
content as well as test weight. The
return to fertilizer N applied above the lowest N rate for each field was also
calculated for a corn price of $4.50/bu and a fertilizer N price of $0.50/lb of
actual N.
Spring nitrate-N at the 0-24” soil
depth exceeded 68 lb/acre in three of the fields. There was little or no yield response to fertilizer N
applications above the low rate in these high testing fields. This is supported by the nitrate-N content
in stalk samples (8” stalk sections taken at 6” above soil surface) from mature
corn stalks. Stalk nitrate-N was very
high, 3,900 ppm, at the lowest N rate in these fields. Stalk test criteria states that N is
deficient at nitrate-N contents of 0-250 ppm, marginal at 250-700 ppm, adequate
at 700-2,000 ppm and excessive when over 2,000 ppm. Stalks tested less than 611 ppm nitrate-N in fields where spring
soil tests were less than 41 lb N/acre and N was applied at the low rate. Data from the 10 fields indicated that when
stalk tests exceeded 1,000 ppm yields were maximized or very close. Stalk nitrate-N contents of more than 2,000
ppm indicated excess N application resulting in elevated soil N in the fall
sampling. Grain protein tended to
increase with increasing N rate to the point yields were maximized. Starch content tended to decrease as grain
protein increased. The fertilizer N
rate that was 50 lb N/acre less than the field rate gave the highest returns in
eight farm fields. Field j
which was corn on corn, returned $15.19 more per acre at the 185 lb/acre N rate
than at the 135 lb/acre N rate.
Field f which was corn on potato ground returned $4.38 more at the
170 lb/acre N rate than at the 120 lb/acre N rate.
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Table
1. The effect of fertilizer N rate on irrigated corn in five
producer fields at Oakes ND, in 2006.
Field |
Fertilizer |
Spring-2006 |
Yield |
Y/Ymax1 |
Stalk |
Fall-2006 |
Grain |
Test |
Return
to |
Crop |
||
Soil |
Soil |
N
Above |
||||||||||
N
Rate |
Nitrate-N |
Nitrate-N |
Nitrate-N |
Oil |
Protein |
Starch |
Weight |
Low
N Rate2 |
2005 |
|||
|
lb/ac |
lb/ac |
bu/ac |
|
ppm |
lb/ac |
% |
% |
% |
lb/bu |
$ |
|
i |
135 |
36 |
207 |
0.97 |
511 |
24 |
2.8 |
8.2 |
74.0 |
58.6 |
|
corn |
i |
185 |
36 |
212 |
0.99 |
1459 |
32 |
3.0 |
8.4 |
73.3 |
59.1 |
-2.05 |
corn |
i |
235 |
36 |
213 |
1.00 |
4057 |
68 |
3.1 |
8.4 |
73.1 |
59.4 |
-22.10 |
corn |
j |
135 |
28 |
198 |
0.95 |
610 |
16 |
3.4 |
7.8 |
73.6 |
59.3 |
|
corn |
j |
185 |
28 |
207 |
0.99 |
1161 |
32 |
3.2 |
8.4 |
73.8 |
58.3 |
15.19 |
corn |
j |
235 |
28 |
209 |
1.00 |
1868 |
32 |
3.4 |
8.6 |
73.1 |
59.4 |
-1.09 |
corn |
k |
100 |
60 |
196 |
1.00 |
1018 |
36 |
2.8 |
8.7 |
72.8 |
60.0 |
|
corn |
k |
150 |
60 |
194 |
0.99 |
2724 |
60 |
2.6 |
8.2 |
73.4 |
59.2 |
-35.31 |
corn |
k |
200 |
60 |
190 |
0.97 |
1894 |
68 |
2.6 |
8.2 |
73.6 |
58.7 |
-76.91 |
corn |
c |
90 |
68 |
237 |
0.97 |
214 |
16 |
3.2 |
8.5 |
73.1 |
61.3 |
|
pinto |
c |
150 |
68 |
242 |
0.99 |
1134 |
36 |
3.2 |
8.8 |
72.8 |
61.1 |
-7.50 |
pinto |
c |
200 |
68 |
244 |
1.00 |
1449 |
88 |
3.2 |
9.0 |
72.7 |
61.5 |
-23.50 |
pinto |
c |
250 |
68 |
244 |
1.00 |
1955 |
160 |
3.1 |
9.2 |
72.6 |
62.2 |
-48.50 |
pinto |
e |
90 |
136 |
225 |
0.97 |
3931 |
176 |
3.1 |
8.7 |
72.5 |
59.1 |
|
pinto |
e |
190 |
136 |
231 |
1.00 |
4104 |
112 |
2.7 |
8.6 |
73.6 |
58.9 |
-22.55 |
pinto |
e |
190 |
136 |
220 |
0.95 |
4477 |
200 |
2.8 |
8.7 |
73.1 |
59.9 |
-72.05 |
pinto |
e |
230 |
136 |
226 |
0.98 |
4113 |
164 |
2.6 |
8.4 |
73.6 |
59.2 |
-65.05 |
pinto |
a |
100 |
40 |
180 |
0.98 |
82 |
52 |
3.2 |
8.2 |
72.8 |
58.9 |
|
potato |
a |
150 |
40 |
175 |
0.96 |
380 |
52 |
3.1 |
8.6 |
73.4 |
61.3 |
-43.45 |
potato |
a |
200 |
40 |
183 |
1.00 |
313 |
160 |
3.0 |
8.8 |
73.0 |
61.1 |
-35.60 |
potato |
f |
120 |
104 |
194 |
0.97 |
7982 |
52 |
2.7 |
8.2 |
73.4 |
59.8 |
|
potato |
f |
170 |
104 |
201 |
1.00 |
6398 |
100 |
2.6 |
8.6 |
73.6 |
60.2 |
4.38 |
potato |
f |
230 |
104 |
195 |
0.97 |
9078 |
140 |
3.1 |
8.7 |
72.6 |
59.9 |
-51.36 |
potato |
g |
120 |
60 |
202 |
0.98 |
1880 |
20 |
3.2 |
7.7 |
72.8 |
59.9 |
|
potato |
g |
170 |
60 |
205 |
1.00 |
6752 |
76 |
2.8 |
7.9 |
73.2 |
60.1 |
-10.82 |
potato |
g |
230 |
60 |
202 |
0.99 |
8337 |
92 |
3.0 |
7.8 |
73.1 |
59.7 |
-52.66 |
potato |
h |
170 |
64 |
214 |
1.00 |
5270 |
88 |
3.0 |
8.2 |
73.4 |
58.9 |
|
potato |
h |
220 |
64 |
211 |
0.99 |
5378 |
196 |
3.1 |
8.2 |
73.4 |
59.8 |
-36.83 |
potato |
h |
270 |
64 |
209 |
0.98 |
8774 |
168 |
2.9 |
8.3 |
73.7 |
60.2 |
-70.75 |
potato |
b |
165 |
106 |
203 |
1.00 |
4043 |
84 |
3.7 |
7.9 |
72.6 |
59.4 |
|
soybeans |
b |
200 |
106 |
201 |
0.99 |
3499 |
192 |
3.5 |
7.7 |
73.3 |
58.4 |
-24.70 |
soybeans |
1Y/Ymax = yield for each N rate in a field divided by the highest yield for a N rate in that field.
2Return to fertilizer N above the low rate in each
field was calculated using $4.50 per bushel corn and $0.50 per lb of actual N.
Corn Response to Fertilizer N Rate in
Six Farm Fields, 2007: The
effect of fertilizer nitrogen-rate on yield and plant-soil nitrogen
relationships was studied in six irrigated corn fields (fields l‑p),
on three farms at Oakes ND, in 2007.
The goal in this study was to compare the results of the field N rate to
a strip within the each field where 40 lb/acre less N was applied. The reduced N rates actually ranged from
30-86 lb/acre less than the field rates.
These strips and the field rate were than compared by yield, soil
nitrate-N content (spring and fall), chlorophyll meter readings at silking,
leaf N at silking, end of season nitrate-N stalk test, grain protein, starch
and oil content as well as test weight.
The nitrate-N content in mature corn stalks was determined on 8-inch
stalk sections taken at 6 inches above the soil surface. Stalk test criteria states that N is
deficient at nitrate-N contents of 0-250 ppm, marginal at 250-700 ppm, adequate
at 700-2,000 ppm and excessive when over 2,000 ppm The return to fertilizer N
applied above the lowest N rate for each field was also calculated for a corn
price of $4.50/bu and a fertilizer N price of $0.50/lb of actual N.
Field |
Fertilizer |
Spring-2007 |
Yield |
Y/Ymax1 |
Chlorophyll |
Chlorophyll |
Leaf N |
Stalk |
Fall-2007 |
Grain |
Test |
Return to |
Crop |
||
Soil |
Readings |
Readings |
at |
Soil |
Weight |
N Above |
|||||||||
N Rate |
Nitrate-N |
At Silk |
Late Aug |
Silking |
Nitrate-N |
Nitrate-N |
Oil |
Protein |
Starch |
lb/bu |
Low N Rate2 |
2006 |
|||
|
lb/ac |
lb/ac |
bu/ac |
|
|
|
% |
ppm |
lb/ac |
% |
% |
% |
|
$ |
|
n |
180 |
44 |
202 |
1.00 |
55.9 |
55.7 |
2.3 |
1008 |
32 |
2.4 |
8.1 |
73.8 |
58.2 |
|
corn |
n |
268 |
44 |
202 |
1.00 |
58.9 |
59.3 |
2.9 |
5764 |
72 |
2.3 |
8.5 |
73.1 |
57.1 |
-46.43 |
corn |
p |
140 |
24 |
197 |
0.96 |
59.4 |
57.2 |
2.1 |
752 |
44 |
2.1 |
7.9 |
73.9 |
58.8 |
|
corn |
p |
180 |
24 |
205 |
1.00 |
58.7 |
58.7 |
2.0 |
1695 |
76 |
2.3 |
8.1 |
73.6 |
58.6 |
17.90 |
corn |
q |
140 |
24 |
192 |
1.00 |
56.8 |
60.6 |
2.1 |
1133 |
48 |
2.6 |
7.7 |
74.2 |
57.0 |
|
corn |
q |
180 |
24 |
186 |
0.97 |
59.5 |
58.4 |
2.7 |
2345 |
252 |
2.5 |
8.4 |
72.9 |
57.4 |
-49.58 |
corn |
l |
180 |
54 |
252 |
0.99 |
57.5 |
58.1 |
2.1 |
1337 |
24 |
2.8 |
8.2 |
72.7 |
58.6 |
|
potato |
l |
220 |
54 |
254 |
1.00 |
58.0 |
59.2 |
3.0 |
5746 |
72 |
2.3 |
8.2 |
74.0 |
58.7 |
-12.08 |
potato |
m |
180 |
44 |
229 |
0.96 |
55.5 |
53.4 |
2.8 |
3571 |
40 |
2.2 |
7.3 |
74.5 |
57.4 |
|
potato |
m |
224 |
44 |
240 |
1.00 |
56.9 |
54.9 |
3.1 |
2862 |
28 |
2.2 |
7.1 |
74.2 |
56.9 |
26.02 |
potato |
m |
268 |
44 |
231 |
0.96 |
55.0 |
54.3 |
2.7 |
8735 |
96 |
2.2 |
7.9 |
74.0 |
57.6 |
-36.03 |
potato |
o |
150 |
38 |
193 |
0.96 |
58.2 |
|
2.3 |
6053 |
44 |
2.5 |
8.2 |
73.6 |
57.7 |
|
potato |
o |
180 |
38 |
202 |
1.00 |
59.2 |
|
2.3 |
5981 |
64 |
2.0 |
8.2 |
74.3 |
57.4 |
21.90 |
potato |
1Y/Ymax = yield for each N rate in a field divided by the highest yield for a N rate in that field.
2Return to fertilizer N above the low rate in each field was calculated using $4.50 per bushel corn and $0.50 per lb of actual N.
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