Oakes Irrigation Research
Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2189, FAX: (701)
742-2700, email: rgreenla@ndsuext.nodak.edu
CABBAGE WEED CONTROL USING
28% N SOLUTION
Richard Greenland
Herbicides currently available for weed control in cabbage are generally applied preplant incorporated (PPI), preemergence (PRE), or after the cabbage has four true leaves. Weeds escaping the PPI or PRE herbicide treatments can become too big to be controlled by post emergence herbicides by the time the cabbage has four leaves. Nitrogen solutions can burn weeds and, because of a waxy cuticle on the cabbage, may not injure cabbage. Other nitrogen solutions have been used successfully to control weeds in cabbage, but the N solution most readily available in this area, 28% N, has not been tested. In this study we looked at three N rates (45, 60, and 75 lbs N/acre), three times of N application (when cabbage had 2, 3, or 5 true leaves), and whether the N application gave sufficient weed control to replace the standard post emergence herbicide (Lentagran).
Table 50. Results of the 1998 cabbage weed control study (individual treatments).
Table 51. Results of the 1998 cabbage weed control study (averaged over variables).
MATERIALS AND METHODS
| Soil: | Maddock sandy loam; pH=7.4; 2.2% organic matter; soil-P and soil-K were very high; soil-S was very low. |
| Previous crops: | 1997 - potato; 1996 - field corn; 1995 - soybean, tomato, and squash. |
| Seedbed preparation: | Disked on 31 October 1997. Multiweeded (field cultivated) twice on April 20 to incorporate herbicide and smooth seedbed and once lightly on April 29 to break up the soil crust. |
| Planting: | Direct seeded cabbage on April 29 with a Stanhay vegetable planter modified to drill barley (1 bu/acre, 6-inch rows) between and parallel to the cabbage rows. Cabbage seeds were spaced 7 inches apart in 16-inch rows. Plants were later thinned to 15 inches apart (about 26,000 plants/acre). Seeds were placed ½ to ¾ inch deep into a flat, fine seedbed. Sprayed Poast + Dash (1.5 pt/acre + 1 qt/50 gal) on May 26 to kill the barley cover crop. |
| Fertilizer: | On April 13, broadcast 14 lbs N/acre and 70 lbs P2O5/acre as 10-50-0, 16 lbs N/acre and 19 lbs S/acre as 21-0-0-24, and 94 lbs K20/acre as 0-0-60. Nitrogen treatments were broadcast sprayed on: May 22 (cabbage 1 to 2 inches tall, 2 true leaves, weeds ¼ to ½ inch tall); May 29 (cabbage 3 inches tall, 3 true leaves, weeds ¼ to ¾ inch tall); or June 11 (cabbage 4 inches tall, 5 true leaves, weeds ½ to 2 inches tall). On June 2 or 3, urea was broadcast at 0, 15, 30, or 75 lbs N/acre to balance the N applied as a herbicide. Each plot received a total of 75 lbs N/acre as 28% N and/or urea. As the final herbicide treatment, we sprayed either 28% N at 72 lbs N/acre or Lentagran at 2 lbs/acre on June 23 and 24 when the cabbage was 8 inches tall and the hairy nightshade was 2 to 5 inches tall. Plots sprayed with Lentagran also received a broadcast application of urea at 75 lbs N/acre. |
| Plots: | Each plot was 6 ft wide by 17 ft long. There was a 2-ft border between plots. The study had 4 reps. |
| Irrigation: | Overhead sprinkler irrigation as needed. |
| Pest Control: | Weeds were controlled using Treflan (1 pt/acre applied preplant incorporated on April 20), Dacthal (10 lbs/acre on May 11) and treatments listed on Table 50. (See also the "fertilizer" section on page 52 for an explanation of the application of 28% N that was used as a herbicide). Sprayed Sevin (1.5 pt/acre on May 20) to control flea beetles. Agree (1 lb/acre on June 3 and June 16), Malathion 57 EC (2 pt/acre on July 24), DiPel (1 lb/acre on June 25, July 1, July 7, July 13, July 20, July 27, Aug 11, and Aug 20) and Asana (8 oz/acre on Aug 5 and Aug 13) controlled cabbage looper and cabbage worm. |
| Harvest: | The center two rows of each plot were harvested on September 21, September 30 or October 1. |
When compared to the lower rates of 28% N and the checks, the highest rate of 28% N slightly reduced early infestations of hairy nightshade but did not affect yield or quality of the cabbage. Time of 28% N application was more important than the rate applied. The 28% N solution suppressed early infestations of hairy nightshade only if applied early (when cabbage had 2 to 3 true leaves). It also increased cabbage plant size, head size, and yield when applied early. This was probably due more to a fertilizer effect than a result of improved weed control. Lentagran controlled hairy nightshade better than the 28% N treatments. It also increased cabbage yield and head size compared to the check or using 28% N solution as the final herbicide application.
A 28% N solution can be used as a herbicide to suppress weeds. It can be sprayed when the cabbage has two true leaves or later without hurting the cabbage. Spraying should be done when weather conditions favor the formation of a thick wax cuticle on the cabbage. Such conditions include warm, dry weather before and after spraying. However, in this study weed control was not improved enough using 28% N to make it a viable treatment unless the cabbage also needs the N fertilizer.
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Table 50. Results of the 1998 cabbage weed control study at the Oakes Irrigation Research Site (individual treatments).
| Nitrogen rate | Application timing | Second application† | Weed control ratings | Plant width June 23 | Yield | Head size | No. of heads | Rotten heads | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Night- shades June 10 | Hairy nightshade | Black nightshade | ||||||||||
| June 23 | July 10 | June 23 | July 10 | |||||||||
| lbs/acre | # of leaves‡ | -------------- 1 to 10 ---------------- | inches | tons/A | lbs/head | 1000s/acre | ||||||
| 45 | 2 | Nitrogen | 3.3 | 5.8 | 6.0 | 9.3 | 9.8 | 16.3 | 53.0 | 4.4 | 24.3 | 1.2 |
| 45 | 2 | Lentagran | 4.3 | 7.0 | 9.5 | 9.3 | 9.8 | 16.8 | 53.4 | 4.4 | 24.0 | 1.2 |
| 45 | 3 | Nitrogen | 4.0 | 6.8 | 6.5 | 9.5 | 9.3 | 12.8 | 42.5 | 3.8 | 22.3 | 3.6 |
| 45 | 3 | Lentagran | 5.8 | 7.5 | 9.8 | 9.5 | 9.8 | 13.5 | 42.2 | 3.7 | 22.6 | 4.1 |
| 45 | 5 | Nitrogen | 2.8 | 5.8 | 6.8 | 9.3 | 10.0 | 13.5 | 33.7 | 3.2 | 20.7 | 4.1 |
| 45 | 5 | Lentagran | 4.3 | 6.5 | 8.8 | 9.8 | 10.0 | 12.8 | 39.0 | 3.7 | 20.9 | 3.6 |
| 60 | 2 | Nitrogen | 5.5 | 8.0 | 8.0 | 10.0 | 10.0 | 14.8 | 41.4 | 3.7 | 22.6 | 3.6 |
| 60 | 2 | Lentagran | 4.8 | 6.5 | 8.5 | 9.5 | 10.0 | 16.3 | 44.4 | 4.0 | 21.9 | 3.4 |
| 60 | 3 | Nitrogen | 4.0 | 6.0 | 6.3 | 9.3 | 10.0 | 11.3 | 29.3 | 3.0 | 19.2 | 5.3 |
| 60 | 3 | Lentagran | 3.8 | 6.3 | 9.3 | 9.8 | 9.8 | 13.0 | 36.1 | 4.0 | 18.3 | 5.3 |
| 60 | 5 | Nitrogen | 2.3 | 6.5 | 7.0 | 9.8 | 10.0 | 12.5 | 30.1 | 3.0 | 19.9 | 6.0 |
| 60 | 5 | Lentagran | 3.8 | 6.0 | 9.0 | 9.5 | 10.0 | 13.3 | 44.5 | 3.8 | 23.3 | 2.9 |
| 75 | 2 | Nitrogen | 7.3 | 8.0 | 9.0 | 9.3 | 10.0 | 14.5 | 41.6 | 3.8 | 22.3 | 4.3 |
| 75 | 2 | Lentagran | 8.3 | 8.5 | 9.3 | 10.0 | 9.8 | 15.0 | 57.6 | 4.8 | 24.3 | 2.4 |
| 75 | 3 | Nitrogen | 4.0 | 6.0 | 6.8 | 10.0 | 10.0 | 13.8 | 36.9 | 4.0 | 18.5 | 5.3 |
| 75 | 3 | Lentagran | 6.8 | 7.8 | 9.3 | 10.0 | 10.0 | 12.3 | 41.8 | 3.8 | 21.9 | 2.9 |
| 75 | 5 | Nitrogen | 4.5 | 7.3 | 7.3 | 10.0 | 9.8 | 13.0 | 33.2 | 3.4 | 19.2 | 5.0 |
| 75 | 5 | Lentagran | 1.8 | 6.5 | 9.3 | 10.0 | 10.0 | 11.8 | 41.0 | 4.0 | 20.4 | 3.4 |
| 0 | -- | Nitrogen | 3.8 | 5.3 | 5.0 | 10.0 | 9.5 | 13.5 | 36.2 | 3.7 | 19.7 | 3.8 |
| 0 | -- | Lentagran | 3.3 | 6.8 | 8.8 | 9.5 | 9.8 | 13.0 | 42.9 | 3.9 | 22.1 | 3.4 |
| LSD (0.05) | 3.2 | NS | 2.1 | NS | NS | 2.1 | 10.4 | 0.7 | 3.0 | 2.4 | ||
| C.V. (%) | 51 | 23 | 18 | 5 | 3 | 11 | 18 | 14 | 10 | 46 | ||
| Probability§ | * | NS | *** | NS | NS | *** | *** | ** | *** | ** | ||
†On June 24 or 25 all plots received a second application to control weeds. The plots were sprayed with either Lentagran (2 lbs/acre) or 28% N solution (72 lbs N/acre).
‡Number of leaves the cabbage plants had when the 28% N was applied the first time.
§Probability that values in the same column are the same. NS >5%. The *, **, and *** equal <5%, <1%, and <0.1%, respectively.
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Table 51. Results of the 1998 cabbage weed control study at the Oakes Irrigation Research Site (averaged over variables not listed in each section).
| Treatment | Weed control ratings | Plant width June 23 | Yield | Head size | No. of heads | Rotten heads |
|||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Night- shades June 10 | Hairy nightshade | Black nightshade | |||||||||
| June 23 | July 10 | June 23 | July 10 | ||||||||
| -------------------- 1 to 10 ---------------------- | inches | tons/acre | lbs/head | 1000s/acre | |||||||
| Nitrogen Rate | |||||||||||
| 45 lbs/acre | 4.0 | 6.5 | 7.9 | 9.4 | 9.8 | 14.3 | 44.0 | 3.9 | 22.5 | 3.0 | |
| 60 lbs/acre | 4.0 | 6.5 | 8.0 | 9.6 | 10.0 | 13.5 | 37.6 | 3.6 | 20.9 | 4.4 | |
| 75 lbs/acre | 5.4 | 7.3 | 8.5 | 9.9 | 9.9 | 13.4 | 42.0 | 4.0 | 21.1 | 3.9 | |
| LSD (0.05) | 1.3 | NS | NS | 0.3 | NS | NS | 4.4 | 0.3 | 1.3 | 1.0 | |
| Application Timing† | |||||||||||
| 2 leaves | 5.5 | 7.3 | 8.4 | 9.5 | 9.9 | 15.6 | 48.6 | 4.2 | 23.2 | 2.7 | |
| 3 leaves | 4.7 | 6.7 | 8.0 | 9.7 | 9.8 | 12.8 | 38.1 | 3.7 | 20.5 | 4.4 | |
| 5 leaves | 3.2 | 6.4 | 8.0 | 9.7 | 10.0 | 12.8 | 36.9 | 3.5 | 20.7 | 4.2 | |
| LSD (0.05) | 1.3 | NS | NS | NS | NS | 0.9 | 4.4 | 0.3 | 1.3 | 1.0 | |
| Lentagran vs. Nitrogen‡ | |||||||||||
| Lentagran | --§ | -- | 9.2 | -- | 9.9 | -- | 44.4 | 4.0 | 21.9 | 3.2 | |
| Nitrogen | -- | -- | 7.1 | -- | 9.9 | -- | 38.0 | 3.6 | 21.0 | 4.3 | |
| LSD (0.05) | NS | NS | 0.7 | NS | NS | NS | 3.6 | 0.2 | NS | 0.8 | |
| C.V. (%) | 50 | 24 | 19 | 5 | 3 | 11 | 18 | 14 | 10 | 46 | |
†Number of leaves the cabbage plants had when the 28% N was applied the first time.
‡On June 24 or 25 all plots received a second application to control weeds. The plots were sprayed with either Lentagran (2 lbs/acre) or 28% N solution (72 lbs N/acre).
§No values given because neither the second application of 28% N nor the Lentagran treatment were applied until later.
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Go to Oakes Irrigation Research Site Weed Control Studies
Go to Oakes Irrigation Research Site 1998 annual report