carrot weed control study 1996

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

CARROT WEED CONTROL STUDY, 1996

Richard G Greenland

Lorox and Treflan controlled most of the weeds in our 1995 carrot weed control study. One question we still needed to answer was when was the best time and the best rates of Lorox to use. This year's study helped answer those questions.

Results summary

Table 57. Carrot heights, stands, injury, and weed ratings.

Table 58. Yields and carrot characteristics.

MATERIALS AND METHODS

Soil: Maddock sandy loam; pH=7.4; 2.6% organic matter; soil-P and soil-K were very high; soil-S was low.

Previous crop: 1995 - soybean; 1994 - carrot; 1993 - winter squash.

Seedbed Preparation: Subsoiled April 24. Disked April 26. Multiweeded (field cultivated) four times; once on May 6 and twice on May 7 to incorporate herbicide and to smooth the seedbed, and once on May 13 very shallow after rains packed the ground.

Planting: Direct seeded 'Presto' carrots on May 16 with a Stanhay vegetable planter. Planting pattern was paired rows (3 inches between rows in the pair) on 16 inch centers. Seeded at about 500,000 seeds/acre.

Plots: Plots were 17 ft long by 6 ft wide and arranged on 8 ft centers (giving a 2-ft check strip between plots). There were 4 reps.

Fertilizer: On April 17, 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. Sprayed 20 lbs N/acre as 28-0-0 on May 3. Side dressed with urea at 75 lbs N/acre on June 19 and 55 lb N/acre on July 9.

Irrigation: Overhead sprinkler irrigation as needed.

Pest control: For Lorox treatments see table 57. All plots received 1.5 lbs Treflan/acre in addition to the Lorox applied. Asana (8 oz/acre sprayed on July 9, and chemigated on July 12 and July 31) was used to control leaf hoppers.

Harvest: Harvested on October 24. Yields, etc. were taken from a five-foot section of two rows harvested from each plot.

RESULTS

Lorox controlled hairy nightshade while not injuring the carrots. A split application controlled nightshade the best. Higher rates were not needed to control nightshade. Lorox controlled sowthistle only when applied post emergence. A split application with at least 1.5 lbs/acre of Lorox post emergence was needed for good control of sowthistle. Yields were highest and carrots were larger where the nightshade was controlled the best.

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Table 57. Carrot heights, stands, injury, and weed ratings for the carrot weed control study, 1996.

Lorox applied 26 June 1996 ratings 8 July 1996 ratings

PRE POST height stand HNS¹ BNS¹ SWTH¹ height injury HNS¹ BNS¹ SWTH¹

-- lbs/acre -- inches 1000s/A ------------ % control -------- inches % ----------- % control -----------

0 0 7.8 154 10 33 88 13.3 0 0 0 65

2 0 6.0 119 100 100 75 11.3 20 98 100 0

0 2 7.4 191 35 40 76 10.5 30 95 95 75

1 1 5.6 143 100 100 93 11.0 20 100 100 90

1½ 1½ 5.6 162 100 100 95 10.3 10 100 100 100

2 1 5.9 155 100 100 98 10.8 20 100 100 90

1 2 5.6 158 100 100 98 10.5 20 100 100 100

2 2 5.8 138 100 100 83 10.5 20 100 100 100

LSD (0.05) 1.1 NS 14 15 16 1.3 10 4 6 ¶

C.V. (%) 12 27 12 12 12 8 40 3 4 ¶

¹Weed names are: HNS = hairy nightshade; BNS = black nightshade; SWTH = sowthistle.

¶Only in reps 3 and 4 was there enough sowthistle to get a rating, so no statistics were calculated. Values in this column are the average of the ratings for reps 3 and 4.

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Table 58. Yields and carrot characteristics for the carrot weed control study, 1996.

Lorox applied Roots/acre Yield Root

PRE POST #1 total #1 multiple root total length diameter size

--- lbs/acre --- ---- 1000s/acre ---- -------------- tons/acre ------------- -------- inches ------- oz/root

0 0 0 c¹ 42 c 0.0 c 0.0 a 1.3 c 3.5 c 1.0 c 0.9 d

2 0 20 bc 88 bc 4.8 bc 7.0 ab 15.8 bc 5.8 b 1.5 b 5.2 c

0 2 59 a 162 a 13.5 a 5.8 ab 28.7 ab 6.7 ab 1.9 a 5.8 bc

1 1 49 ab 136 ab 12.4 a 19.9 bc 38.4 a 7.0 a 1.8 a 8.8 ab

1½ 1½ 44 ab 138 ab 12.6 a 25.5 c 42.1 a 6.8 a 1.9 a 9.7 a

2 1 61 a 173 a 13.5 a 21.3 c 44.4 a 6.6 ab 1.9 a 8.2 ab

1 2 27 bc 117 ab 7.9 ab 16.8 bc 30.7 ab 6.6 ab 2.0 a 7.9 abc

2 2 41 ab 139 ab 9.3 ab 20.0 c 35.7 a 6.6 ab 1.9 a 8.1 ab

C.V. (%)
49 30 48 58 39 10 9 26

¹Values in the same column followed by the same letter are not significantly different at the 0.05 level.

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Go to Oakes Irrigation Research Site Weed Control Studies

Go to Oakes Irrigation Research Site 1996 annual report

Go to Oakes Irrigation Research Site crop index

Go to Oakes Irrigation Research Site home page

Soil:	Maddock sandy loam; pH=7.4; 2.6% organic matter; soil-P and soil-K were very high; soil-S was low.
Previous crop:	1995 - soybean; 1994 - carrot; 1993 - winter squash.
Seedbed Preparation:	Subsoiled April 24. Disked April 26. Multiweeded (field cultivated) four times; once on May 6 and twice on May 7 to incorporate herbicide and to smooth the seedbed, and once on May 13 very shallow after rains packed the ground.
Planting:	Direct seeded 'Presto' carrots on May 16 with a Stanhay vegetable planter. Planting pattern was paired rows (3 inches between rows in the pair) on 16 inch centers. Seeded at about 500,000 seeds/acre.
Plots:	Plots were 17 ft long by 6 ft wide and arranged on 8 ft centers (giving a 2-ft check strip between plots). There were 4 reps.
Fertilizer:	On April 17, 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. Sprayed 20 lbs N/acre as 28-0-0 on May 3. Side dressed with urea at 75 lbs N/acre on June 19 and 55 lb N/acre on July 9.
Irrigation:	Overhead sprinkler irrigation as needed.
Pest control:	For Lorox treatments see table 57. All plots received 1.5 lbs Treflan/acre in addition to the Lorox applied. Asana (8 oz/acre sprayed on July 9, and chemigated on July 12 and July 31) was used to control leaf hoppers.
Harvest:	Harvested on October 24. Yields, etc. were taken from a five-foot section of two rows harvested from each plot.

Lorox applied		26 June 1996 ratings					8 July 1996 ratings
PRE	POST	height	stand	HNS¹	BNS¹	SWTH¹	height	injury	HNS¹	BNS¹	SWTH¹
-- lbs/acre --		inches	1000s/A	------------ % control --------			inches	%	----------- % control -----------
0	0	7.8	154	10	33	88	13.3	0	0	0	65
2	0	6.0	119	100	100	75	11.3	20	98	100	0
0	2	7.4	191	35	40	76	10.5	30	95	95	75
1	1	5.6	143	100	100	93	11.0	20	100	100	90
1½	1½	5.6	162	100	100	95	10.3	10	100	100	100
2	1	5.9	155	100	100	98	10.8	20	100	100	90
1	2	5.6	158	100	100	98	10.5	20	100	100	100
2	2	5.8	138	100	100	83	10.5	20	100	100	100

LSD (0.05)		1.1	NS	14	15	16	1.3	10	4	6	¶
C.V. (%)		12	27	12	12	12	8	40	3	4	¶

Lorox applied		Roots/acre		Yield			Root
PRE	POST	#1	total	#1	multiple root	total	length	diameter	size
--- lbs/acre ---		---- 1000s/acre ----		-------------- tons/acre -------------			-------- inches -------		oz/root
0	0	0 c¹	42 c	0.0 c	0.0 a	1.3 c	3.5 c	1.0 c	0.9 d
2	0	20 bc	88 bc	4.8 bc	7.0 ab	15.8 bc	5.8 b	1.5 b	5.2 c
0	2	59 a	162 a	13.5 a	5.8 ab	28.7 ab	6.7 ab	1.9 a	5.8 bc
1	1	49 ab	136 ab	12.4 a	19.9 bc	38.4 a	7.0 a	1.8 a	8.8 ab
1½	1½	44 ab	138 ab	12.6 a	25.5 c	42.1 a	6.8 a	1.9 a	9.7 a
2	1	61 a	173 a	13.5 a	21.3 c	44.4 a	6.6 ab	1.9 a	8.2 ab
1	2	27 bc	117 ab	7.9 ab	16.8 bc	30.7 ab	6.6 ab	2.0 a	7.9 abc
2	2	41 ab	139 ab	9.3 ab	20.0 c	35.7 a	6.6 ab	1.9 a	8.1 ab

C.V. (%)		49	30	48	58	39	10	9	26