Some 1997 Results of Field
Research in Fond du Lac Co.
Pre-plant Nitrogen Test
Verification
At the Brian Costello farm in Malone, pre-plant soil nitrate tests (PPNT) were taken on a field in spring, 1997 that was alfalfa in 1995, corn in 1996 [manure applied in spring with no additional fertilizer nitrogen (N) applied to crop], and again planted to corn in 1997. Surprisingly, the PPNT measured 266 lbs. of available N per acre with a recommendation that no further applications of N be made for the 1997 corn crop. To verify this recommendation, field strips were established in a randomized complete block design (3 replications). Treatments were 0, 50, and 100 lbs. per acre of applied sidedress N as anhydrous ammonia (NH3). Yield results (adjusted to 13.5% moisture) were as follows:
Treatment Yield
(bu/ac)
--------------------------------
0 lbs. N 126.8
50 lbs. N 131.6
100 lbs. N 132.4
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Although the 0 N treatment yielded 5 bushels per acre less than the 50 lb. treatment, the price of corn would have to be $3.00 per bushel to even have made the application a "break-even" proposition. Most fields in this situation would receive at least the 100 lb. N per acre rate. The PPNT and it's cousin, the pre-sidedress nitrogen test (PSNT) are useful tools that can often save producers significant input dollars. In another field on the same farm, the PPNT test recommended a N application rate of 63 lbs. per acre. The double replicated field plots confirmed the recommendation with no additional yield gain from an N application above 50 lbs. per acre.
On fields that are in a rotation with alfalfa and where manure is applied, these trials emphasize the importance of not over applying N. At the very least, take the appropriate N credits for both the manure and legume crop. To make further modifications in the N rate, utilize either the PPNT or PSNT.
Grass Control Timing in Corn
In a field that had a history of heavy foxtail infestation, a grass control timing field plot was done on the Dave Thompson farm near Waucousta. Plots were 10' X 25' established in a randomized complete block design (4 replications). Broadleaf control was uniformly accomplished across the entire plot area using a post-emerge application of Banvel (dicamba). Recommended rates of the respective grass herbicides were used. Grass control treatments and corn yields were as follows:
Time of Application Herbicide
Yield (bu/ac)
--------------------------------------------------------
Untreated Check -------
54.6
Pre-emerge Dual
II 117.6
1-2 inch grass Basis
85.7
3-4 inch grass Accent
120.9
7-8 inch grass Accent
113.9
10-12 inch grass Accent
90.0
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The low yield of the check plot is testament to the high amount of foxtail present in the plot area. The highest yield was obtained when grass was controlled at the 3 - 4 inch height. Not surprisingly, this is the recommended optimum height to control annual grass in corn. Like other Midwest university and company weed control studies have verified, corn yields were reduced when control occurred after the grass became taller than 3 to 4 inches even though control at the 7 to 8 inch height was effective. Yield reductions are most likely caused by early season weed competition with the crop and emphasize the importance of a timely herbicide application. In this study, control of foxtail at the 1 to 2 inch height was initially good but control broke down as the season progressed (Basis would normally not be recommended for foxtail infestations with no mechanical cultivation imposed). The pre-emerge treatment of Dual performed nearly as well as the Accent application at 3 to 4 inches. This was the result of a 0.5 inch rain the day following the pre-emerge application. Where rain doesn't follow pre-emerge applications, we often see less than desirable performance.
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