Oakes
STRIP-TILL N RATES, CORN ON SOYBEAN
W. Albus, L. Besemann and
H. Eslinger
A strip-tilled corn/soybean
rotation was initiated in 2007. The
corn/soybean and soybean/corn treatments are present each year and rotated with
each other. In the corn on soybean year
of the rotation, N rates are studied.
Soil: |
Embden loam and
Gardena loam; pH=6.8; 2.5% organic matter; soil-P and soil-K was very high;
soil-S was high. |
Previous crop: |
2006 – soybean and edible
bean; 2005 – cabbage, broccoli and pumpkin; 2004 – field corn. |
Seedbed Preparation: |
Strip-tilled on November 13,
2006, with a shank machine with leading coulters, row cleaners, anhydrous
knives and closing disks |
Planting: |
Planted Midwest 69704
VT3 treated with Crusier seed treatment on April 26 @ 33,000 plants per acre
in 30 inch rows. |
Plots: |
Plots were 35.5 ft
long by 15 ft (6 rows) wide. There
were four reps. |
Fertilizer: |
November 2006, During the strip-till operation
applied 15 lbs N/acre and 51 lbs P2O5/acre as 10-34-0.
May 7 applied 35 lbs N/acre as 32-0-0 to all plots except the zero
N-rate plots. June 8 applied 50 lbs
N/acre to the 100 lb N-rate plots and 100 lbs N/acre to the 150 lb N-rate
plots as 32‑0‑0. |
Irrigation: |
Overhead sprinkler
irrigation as needed. |
Pest control: |
Aim (⅔
oz/acre) + Glyphosate (2 qt/acre) + NIS (0.5% v/v) + AMS (1 lb/10 gal)
on May 9, Lumax (3 pt/acre) on May 16, Cornerstone (32 oz/acre) + AMS (1
lb/10 gal) + Interlock + (4 oz/acre) on May 29, |
Harvest: |
Hand harvested
October 9 and October 10. Two
ten-foot sections from the two center rows from each plot (forty feet of
total row). |
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top of strip-till n rates, corn on soybean
Previous soybean ground was strip-tilled on November 13,
2006. Mole knives were set to a 6-inch
depth and banded 13 gal/acre of 10-34-00 (15 lb/acre N applied). The fertilizer N rates were 15, 50, 100, and
150 lb/acre. There were two 15 lb/acre
N rate treatments. Chlorophyll meter
readings were taken on the ear leaves on July 20 and August 16. Leaves opposite and below the ear were
sampled at silking for total N content.
After the corn was mature (R6) eight-inch sections of the stalks were
taken at a height six inches above the soil leveland tested for nitrate-N
(commonly called the Iowa stalk test).
There are four categories for this test: low (less than 250 ppm),
marginal (250-700 ppm), optimum (700-2000 ppm) and excess (greater than 2,000
ppm).
Yield increased with increased N
rates. Test weights increased with
increased N rates above 50 lb/acre.
Soil nitrate-N decreased from 31 lb N/acre in the spring to 17 lb
N/acre in the fall. Stalk nitrate-N was
below 100 ppm for all N rates. This
suggests that yield was not maximized at the 150 lb/acre N rate. Chlorophyll meter readings, leaf N content
at silking and grain protein content were good indicators of yield.
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corn on soybean
Table 1. The response of strip-till irrigated corn to fertilizer nitrogen on land previously soybean at the Oakes Irrigation Research Site in 2007.
Fertilizer |
Yield |
Grain |
Test |
Nitrate-N |
Chlorphyll
reading1 |
Leaf-N2 |
Silking |
Stalk |
Grain |
||
N Rate |
Moist |
Weight |
Spring-06 |
Fall-07 |
7/20/2007 |
8/16/2007 |
at
silking |
date |
Nitrate-N |
Protein |
|
|
bu/ac |
% |
lb/bu |
lb/ac |
lb/ac |
---------
# --------- |
% |
|
ppm |
% |
|
|
|||||||||||
15 |
91 |
21.8 |
55.2 |
35 |
15 |
30.5 |
25.8 |
1.05 |
7/21/07 |
38 |
5.73 |
15 |
97 |
21.5 |
54.9 |
31 |
15 |
31.5 |
26.6 |
1.10 |
7/21/07 |
40 |
5.73 |
50 |
125 |
20.6 |
54.1 |
28 |
16 |
36.2 |
30.0 |
1.23 |
7/17/07 |
78 |
5.78 |
100 |
172 |
20.6 |
55.4 |
28 |
17 |
47.5 |
38.7 |
1.65 |
7/17/07 |
49 |
6.08 |
150 |
207 |
20.1 |
56.9 |
31 |
21 |
54.5 |
50.2 |
2.13 |
7/16/07 |
96 |
6.93 |
|
|||||||||||
MEAN |
138 |
20.9 |
55.3 |
31 |
17 |
40 |
34.3 |
1.43 |
7/18/07 |
60 |
6.1 |
C.V. % |
5 |
5.4 |
1.0 |
22.1 |
30 |
3.8 |
5.9 |
15.40 |
0.0 |
47.2 |
4.5 |
LSD (0.05) |
9.9 |
1.74 |
0.8 |
10.5 |
8 |
2.3 |
3.1 |
0.3 |
1.9 |
43.7 |
0.4 |
1Chlorophyll reading taken on the primary ear
leaf.
2Leaf-N taken from the leaf opposite and below the primary ear leaf.
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