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

PUMPKIN COVER CROP AND LIVING MULCH STUDY, 2001

Richard Greenland

Results summary

Table 52. Treatments

Table 53. Number of fruits and pumpkin yield response to a barley cover crop & living mulches

Table 54. Pumpkin plant size and weed control as affected by cover crop and living mulches

Table 55. Living mulch height and vigor, barley cover, and dry matter accumulation

Pumpkins are planted in wide rows, leaving large areas of bare ground. In current pumpkin production, the between-row area is usually cultivated early in the season before the plants begin to run to control weeds. This exposes the soil to erosion and also reduces soil organic matter. Later in the season hand weeding is used to control weeds. After harvest of pumpkins, little residue is left to protect the soil and it is usually too late in the season for cover crop establishment. Cover crops and living mulches planted between the pumpkin rows could prevent soil erosion and increase soil organic matter, but if they compete too much with the pumpkins then pumpkin yield could be reduced. In this study a barley cover crop was planted in early spring, leaving unplanted strips, 3 ft wide, for planting pumpkins in mid- to late-May. When the barley headed, it was flailed and a living mulch (hairy vetch, rye, soybean, and/or corn) was planted between the pumpkin rows. Data on height, stand, and vigor of pumpkin, living mulches, and weeds were collected to determine competitiveness of the living mulches. Total dry matter was measured at the end of the season. Our objective was to find a cover crop/living mulch combination that protects the soil, helps control weeds, but doesn’t compete with the pumpkins enough to reduce pumpkin yield.

MATERIALS AND METHODS

Soil:	Maddock Sandy Loam; pH=7.6; 2.0% organic matter; soil-K was very high; soil-P was high; soil-S was very low.
Previous crops:	2000 - carrot and potato; 1999 - sweet corn and cabbage; 1998 - cabbage, carrot, cauliflower, radish, broccoli and oriental vegetables.
Seedbed preparation:	Disked once on April 17 or 20. Multiweeded (field cultivated) once on April 19 or 20.
Planting:	Pumpkin seeds planted 1 ft apart in rows 8 ft apart on May 18. On June 20 thinned to an in-row spacing of one plant every 3 ft.
Plots:	Plots were 20 ft long by 16 ft (two rows) wide.
Fertilizer:	On April 19, broadcast 10 lbs N/acre and 50 lbs P₂O₅/acre as 10-50-0 and 18 lbs N/acre and 20 lbs S/acre as 21-0-0-24. On April 25 sprayed 50 lbs N/acre as 28-0-0. Side dressed 35 lbs N/acre as urea on June 20.
Irrigation:	Overhead sprinkler irrigation as needed.
Pest control:	Weeds were controlled by hand weeding on all plots and by weed control treatments given in Table 52. Sprayed Asana (8 oz/acre on July 19, Aug 8, and Aug 15) and Sevin (1 qt/acre on Jul 30) to control cucumber beetles. Sprayed Ridomil MZ72 (2.5 lbs/acre on July 24 and Aug 15), Topsin (0.41 lb/acre on Aug 1), and Maneb (2 lb/acre on Aug 1) to control disease.
Harvest:	Hand harvested September 10 to September 18.

RESULTS

A barley cover crop planted between pumpkin rows reduced pumpkin yield slightly but decreased pumpkin diseases. Living mulches of hairy vetch, soybean, and/or corn planted between pumpkin rows increased dry matter accumulation and helped protect the soil with little or no reduction in pumpkin yield. Rye did not grow well (probably due to allelopathy from the flailed barley) and is not recommended as a living mulch when planted into flailed barley. Hairy vetch started out slowly but produced a dense cover. Soybean had as much dry matter as hairy vetch, grew quicker, but also died earlier. A later maturing soybean may be better. Corn produced the highest amount of dry matter, but also competed with the pumpkins the most. Soybean and corn suppressed weeds better than hairy vetch or rye.

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Table 52. Treatments applied to the Oakes Irrigation Research Site 2001 pumpkin cover crop/living mulch study.

Cover crop/living mulch treatments¹

No barley cover crop; no living mulch (check)

Barley cover crop; no living mulch

Barley cover crop; hairy vetch

Barley cover crop; rye

Barley cover crop; hairy vetch + rye

Barley cover crop; soybean

Barley cover crop; soybean + corn

Barley cover crop; corn

Weed control treatments

Herbicide - Buctril (1 pt/acre on May 18 before planting pumpkin) and Poast + Dash (1.5 + 1 pt/acre on June 15 just before flailing barley) applied to entire plot.

No herbicide - The 3 ft strips were cultivated just before planting pumpkins.

Note: Only the 3-ft wide strip the pumpkins were planted in was hand weeded. The area between the pumpkin rows was not weeded except for the check (no barley, no living mulch).

Barley flail height treatments²

High - flailed at 1 ft high

Low - flailed at less than 1 inch high

¹Barley was planted with a drill (6-inch row spacing) on April 26 in strips 5 ft wide, leaving 3-ft

wide bare strips for planting pumpkins. Living mulches were no-till planted on June 21 or 22

with a Monosem specialty planter in 18-inch rows into the barley cover crop that had been

flailed. A trash whipper was used ahead of the planter units to move the barley away from the

planted row. Where two living mulches were planted, they were planted in alternating rows.

²Barley was flailed on June 18. This was just after barley headed, when the pumpkins began

to run, and before planting the living mulches.

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Table 53. Number of fruits and pumpkin yield response to a barley cover crop and living mulches in the Oakes Irrigation Research Site 2001 pumpkin cover crop/living mulch study.

Treatments	Number of pumpkins				Pumpkin yield				Fruit size
Treatments	marketable	not marketable¹	green	total	marketable	not marketable¹	green	total	Fruit size
	------------------ number per acre ------------------				--------------- tons per acre ---------------				lbs/fruit
Cover crop, living mulch
No barley, no mulch	3810	620 a²	850 a	5350 a	19.8	2.5 a	2.7 a	25.0 a	10.4 a
Barley, no mulch	3630	420 abc	550 b	4540 b	16.7	1.5 b	1.4 b	19.7 bc	9.5 b
Barley, hairy vetch	3570	380 bc	410 bcd	4470 bc	17.0	1.6 b	1.2 bc	19.8 bc	9.4 b
Barley, rye	3510	440 ab	450 bcd	4520 b	17.2	1.8 ab	1.4 b	20.4 b	9.7 b
Barley, hairy vetch + rye	3480	400 bc	480 bc	4300 bcd	16.7	1.5 bc	1.5 b	19.6 bc	9.8 b
Barley, soybean	3430	410 abc	410 bcd	4320 bcd	16.6	1.6 b	1.1 bc	19.4 bc	9.6 b
Barley, soybean + corn	3400	210 c	280 d	3990 cd	16.4	0.7 c	0.8 c	18.0 bc	9.6 b
Barley, corn	3250	300 bc	330 cd	3910 d	15.4	1.0 bc	1.0 bc	17.4 c	9.5 b

Probability	0.57	0.05	<.0001	0.0006	0.16	0.01	<.0001	0.0014	0.046
Herbicide treated
No	3440	370	490	4340	16.4	1.4	1.5	19.2	9.5
Yes	3580	430	450	4510	17.6	1.7	1.3	20.6	9.8

Probability³	0.22	0.31	0.49	0.09	0.10	0.37	0.38	0.09	0.04

C.V. (%)⁴	11	58	62	10	10	55	72	8	8
Barley flail height
High	3500	340	450	4330	16.4	1.2	1.3	18.9	9.4
Low	3440	390	380	4270	16.8	1.6	1.1	19.4	9.8

Probability³	0.57	0.07	0.13	0.58	0.49	0.02	0.20	0.36	0.012

C.V. (%)	10	65	58	8	9	62	69	6	8

¹Not marketable were those pumpkins that had disease spots, small rotten spots, major blemishes, or very odd shapes. (Most of the

time it was disease spots).

²Values in the same column followed by the same letter are not significantly different at the 0.05 level. If no letters follow values in a

column then there were no significant differences between values in that column.

³The two values immediately above the probability value are significantly different only if the probability is less than 0.05.

⁴This C.V. applies to cover crop/living mulch treatments and to herbicide treatments. The other C.V. applies to flail height treatments.

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Table 54. Pumpkin plant size and weed control as affected by cover crop and living mulches in the Oakes Irrigation Research Site 2001 pumpkin cover crop/living mulch study.

Treatment	Pumpkin			Weed ratings on August 17
Treatment	width July 23	vigor July 23	% ground cover Aug 17	redroot pigweed	lambs- quarters	hairy nightshade	black nightshade	foxtail¹
	1 to 8	1 to 10²	%	------------------------ 1 to 10² ---------------------
Cover crop/living mulch
No barley, no mulch	7.7 a²	8.3 a	94 a	9.9 a	10.0 a	9.8 a	10.0 a	9.8
Barley, no mulch	6.7 b	7.1 b	76 bc	9.3 cd	8.7 bc	6.5 c	9.1 bc	9.3
Barley, hairy vetch	6.7 b	7.1 b	79 b	9.1 d	8.3 c	6.4 c	8.6 c	9.3
Barley, rye	6.6 b	7.0 b	78 bc	9.0 d	8.3 c	6.4 c	8.6 c	9.3
Barley, hairy vetch + rye	6.8 b	7.3 b	79 b	9.4 bcd	8.7 bc	5.9 c	8.8 bc	9.4
Barley, soybean	6.6 b	7.0 b	78 bc	9.7 abc	8.9 b	7.6 b	8.9 bc	9.6
Barley, soybean + corn	6.6 b	7.2 b	73 bc	9.8 ab	9.0 b	7.6 b	8.9 bc	9.4
Barley, corn	6.6 b	7.3 b	72 c	9.7 abc	9.2 b	8.0 b	9.4 ab	9.6

Probability	<.0001	0.0001⁴	<.0001⁴	0.0004⁵	<.0001	<.0001	0.02	0.91
Herbicide treated
No	6.7	7.1	76	9.6	8.4	6.8	8.8	9.1
Yes	6.9	7.4	81	9.4	9.3	7.8	9.2	9.9

Probability⁶	0.15	0.25⁴	0.04⁴	0.015	0.005	0.053	0.054	0.008

C.V. (%)⁷	5	6	9	5	6	13	7	8
Barley flail height
High	6.5	7.0	74	9.9	8.3	6.8	8.9	9.3
Low	6.8	7.3	78	8.9	9.1	7.0	8.9	9.5

Probability⁶	0.02	0.01	0.11	0.0002⁵	0.002	0.56	1.00	0.42

C.V. (%)	5	5	9	6	6	11	7	7

¹Green and yellow foxtail.

²Weed ratings from 0 (no weed control or no pumpkin vigor) to 10 (complete weed control, very vigorous pumpkin plants)

³Values in the same column followed by the same letter are not significantly different at the 0.05 level.

⁴Interaction - Pumpkin vigor and pumpkin % ground cover responded more to herbicide treatments on low growing living mulches.

⁵Interaction - Barley flail height was more important in pigweed control with short or no living mulches than with tall living mulches.

⁶The two values immediately above the probability value are significantly different only if the probability is less than 0.05.

⁷This C.V. applies to cover crop/living mulch treatments and to herbicide treatments. The other C.V. applies to flail height treatments.

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Table 55. Living mulch height and vigor, barley cover, and dry matter accumulation in the Oakes Irrigation Research Site 2001 pumpkin cover crop/living mulch study.

Treatments	July 23			August 17		Total dry matter² (mid Oct.)
	living mulch		barley cover¹	living mulch
	height	vigor	barley cover¹	height	vigor
	inches	1 to 10	%	inches	1 to 10	tons/acre
Cover crop/living mulch
No barley, no mulch	—	—	—	—	—	2.2 c
Barley, no mulch	0.0 e³	0.0 e	26	0.0 f	0.0 e	5.8 b
Barley, hairy vetch	6.7 d	6.0 b	28	12.9 d	6.3 b	7.2 b
Barley, rye	5.1 d	3.5 d	26	7.1 e	1.7 d	5.9 b
Barley, hairy vetch + rye	5.5 d	4.4 c	28	8.9 e	3.3 c	7.1 b
Barley, soybean	12.7 c	7.2 a	26	23.9 c	7.9 a	7.5 b
Barley, soybean + corn	19.4 b	6.8 a	26	34.4 b	7.2 ab	9.7 a
Barley, corn	27.7 a	7.1 a	29	46.6 a	6.7 b	10.3 a

Probability	<.0001	<.0001	0.65	<.0001	<.0001	<.0001
Herbicide treated
No	10.9	4.8	34	18.7	4.6	7.2
Yes	11.1	5.1	20	19.6	4.9	6.7

Probability⁴	0.77	0.048	0.03	0.09	0.09	0.20
Barley flail height
High	9.9	4.4	46	17.3	4.2	7.6
Low	12.1	5.6	08	20.9	5.3	7.6

Probability⁴	0.02	0.0004	<.0001	0.0004	0.0002	0.90

C.V. (%)	17	16	19	10	14	20

¹Percent of plot covered with the barley cover crop.

²From these we estimate that the pumpkin vines, barley plus weeds, rye, hairy vetch, soybean, and corn contributed 2.2, 3.6, 0, 1.4,

1.7, and 4.5 tons of above ground dry matter/acre, respectively.

³Values in the same column followed by the same letter are not significantly different at the 0.05 level. If no letters follow values in a

column then there were no significant differences between values in that column.

⁴The two values immediately above the probability value are significantly different only if the probability is less than 0.05.