Comparison of Three Different WeedGuardPlus Paper Mulches and Black Plastic
Mulch on the Production of Winter Squash
Dr. Frank Stonaker, Colorado State University Department of Horticulture and Landscape
Architecture, Assistant Professor and Coordinator of Specialty Crops Program.
Dan Goldhamer Colorado State University Department of Horticulture and Landscape
Architecture, Research Associate.
Introduction
Previous work with WeedGuardPlus by M.D. Orzolek and B. Dye in 2008 indicated that
WeedGuardPlus my increase the yield of winter squash compared to both a bare ground control
and a non-degradable black plastic mulch. It was the aim of the this study to evaluate the effect
of 3 types of WeedGuardPlus on the production of delicata winter squash compared to both a
bare ground control and black plastic mulch. The specific variables observed were the yield per
plant, number of fruit per plant, average fruit weight, and seedling emergence.
Materials and Methods
Trials were conducted at the Colorado State University Horticulture Field Research Center in
northeast Fort Collins, Colorado. In order to evaluate the effect of WeedGuardPlus on winter
squash production, 5 total mulch treatments were utilized with 3 replications of each treatment.
The plot design was as randomized complete block with 3 replications. The 5 treatments were:





WeedGuardPlus creped regular weight
WeedGuardPlus creped heavy weight
WeedGuardPlus regular weight
Black plastic
Bare ground control.
Each plot was 180” long and 60” wide. Within each plot, 10 plants of a bush delicata winter
squash (Cucurbita pepo) spaced 18” apart. Seeding was done by hand and 3 seeds were placed
per 18”. Plants were thinned to one plant per 18” after emergence. The creped WeedGuardPlus
mulch and plastic mulch were laid by a tractor mounted mulch layer while the WeedGuardPlus
regular was laid by hand. The mulch was laid out on June 7th 2011 and seeding of the winter
squash occurred on the same day. Soil tests were performed prior to mulch application and soil
was amended with composted manure to achieve a rate of 150 lbs of available Nitrogen per acre.
Irrigation was supplied daily using drip tape applied beneath the weed barrier, and set on an
irrigation timer.
Harvest occurred on October 2nd. Harvest was perfumed by hand and all fruit were collected.
Fruit under 4” in length were discarded and not included in the analysis. Statistical analysis was
performed using SAS 9.2.
Results
Figure 1 outlines the average yield per plant. There was no observed statistical difference
between the treatments (p=0.6478).
Average Yield per Plant
4.5
4
3.5
Lbs.
3
2.5
2
1.5
1
0.5
0
Creped regular
Plastic
Creped Heavy
Bare
Regular
Figure 1. The average yield per winter squash plant. No statistical
difference between treatments was observed.
Figure 2 outlines the observed average number of fruit per plant. There was no statistical
difference between the mulch treatments (p=0.677).
Average Number of Fruit per Plant
4
3.5
3
2.5
2
1.5
1
0.5
0
Creped regular
Plastic
Creped Heavy
Regular
Figure 2. The average number of fruit per winter squash plant. No
statistical difference between treatments was observed.
Bare
Figure 3 outlines the observed average fruit weight. There was no statistical difference between
treatments (p=0.520).
Average Fruit Weight
1.3
1.25
Lb.s
1.2
1.15
1.1
1.05
1
0.95
Creped Heavy
Plastic
Creped regular
Regular
Bare
Figure 3. The average winter squash fruit weight. No statistical difference
between treatments was observed.
Figure 4 outlines the average seedling emergence. A statistical difference between the
treatments was observed (p=0.026). There was no difference in the emergence between the
plastic mulch and any of the paper mulches. The only statistical difference was that the plastic
mulch had a higher emergence rate compared to the bare ground control.
Average Seedling Emergence Rate
90
a
Percent Emergence
80
ab
70
ab
ab
60
50
40
b
30
20
10
0
Plastic
Creped Heavy
Creped regular
Regular
Bare
Figure 4. Average winter squash seedling emergence. Differing letters
signify statistical differences at p=0.05 according to least square means
utilizing the Tukey adjustment.
Discussion
The lack of statistical difference between the treatments may indicate that the paper mulches
were as effective as the plastic mulch. However, there was no difference between the bare
ground control and the paper mulches in any of the categories. Yet, the creped regular weight,
creped heavy weight, and plastic mulches were all similar in their values of yield per plant,
number of fruit per plant, average fruit weight, and seedling emergence. On the other hand, the
values of regular weight creped paper and bare ground treatments were consistently lower than
the other treatments. The lack of significance between these two groups is likely due to the high
variability we observed between plots. This could be due to multiple factors that include but are
not limited to the weed pressure and abnormalities in the manufacturing processes of the
creped mulches that resulted in inconsistencies in the material’s structure.
Perennial and annual weed pressure and in particular bindweed (Convolvulus arvensis) was
intense in this field and both the paper and plastic mulches were eventually compromised by
bindweed (images 1, 2, and 3). This weed pressure may have contributed to the variability in our
observations due to the patchy distribution of the bindweed population. Plots with a higher
bindweed population may have been more negatively impacted compared to others.
Additionally, the creped mulches degraded faster than expected and this reported problem was
possible due to the irregularities in the manufacturing of the product. This irregularity may have
led to the matted look of the mulch as well as its more rapid than expected decomposition.
Image 1. Creped regular weight at time of
harvest (10/2/2011)
Image 2. Creped heavy weight at time of
harvest (10/2/2011)
Image 3. Plastic mulch at time of harvest (10/2/2011)
Overall, the use of WeedGuardPlus paper mulches for the production of winter squash did not
lead to an increase in yields compared to the plastic mulch as observed in a previous study. The
paper mulch however did perform as well as the plastic much with the creped treatments
performing better than the regular treatment thought the results were not significant. Special
consideration for the use of WeedGuardPlus in winter squash production should be made for
the growth habit of the winter squash variety. We chose a bush type of winter squash for this
study due to the wet cold spring of 2011 in Colorado. The bush type of delicata is quicker to
mature and we wanted to ensure a harvest for this study. A winter squash with a more vining
habit might be suited for WeedGuardPlus because of its increased leaf area and canopy cover.
Ideally, once the WeedGuardPlus begins to deteriorate later in the season, the vining type
winter squash would have established a well shaded canopy that would prevent weeds from
establishing in rips and tears. This would lead to better season-long weed control compared to
the more open canopy of bush type winter squash.
Overall WeedGuardPlus performed well as an alternative to plastic mulch though more work in
developing ideal best management practices should be pursued. There are possible further
directions of research that could be continued. First, looking at the effect of WeedGuardPlus on
the survival rate of transplants of winter squash compared to black plastics. Second, exploring
methods to ensure greater seed emergence possibly through the use of pre-punched holes.
Finally, one should explore the effect of creping in both the length the paper alone and creping
in both the length and width of the paper to see if the creping increases durability. Also these
other types of creping may impact performance positivity or negatively due to the increased
surface are compared to the non-creped paper.