A California study looking at the use of plastic mulches on bell peppers
showed significant yield increases and earlier production over non-treated
plots.
Reporting there work at Plasticulture ’05, held March 5-8 in
Charleston, S.C., Richard Molinar, Don May and Blaine Hanson of the
University of California Cooperative Extension, Fresno, Calif., noted
that the best yield was with the Natural 11 treatment. The treatment
yielded 559 cartons per acre in one pick (or 659 cartons per acre
if two picks had been done) over the non-plastic treatment.
California’s vegetable industry is the largest and most diverse
in the world. Plastic mulches are used commercially in peppers and
other crops for a variety of reasons, although, overall, the total
usage of plastic remains quite small. Plastic is generally used to
increase yield, control weeds, protect fruit from rain and soil contact
and promote earlier harvest. This particular study evaluated different
colors and formulations of plastic in bell peppers and cantaloupes.
The bell pepper study was conducted in 2003, according to Molinar,
with the researchers evaluating different colors of plastic mulches
for earliness, weed control, yield, fruit quality and plastic longevity.
The bell pepper beds were 66inches wide. One hundred pounds of 11-52-0
was applied pre-plant in the bed and high flow drip tape was laid
tow inches deep and in the center of the beds. The Jupiter variety
was transplanted on March 3, with holes spaced 12 inches apart down
the row and two rows per bed 18 inches apart. Nitrogen applications
started on April 1 with 12 weekly applications of 20 lbs. of N per
acre using UN32. A total of 252 lbs. of N was applied throughout the
season.
The bell peppers were hand harvested one time when approximately one-third
of the fruit was red of chocolate colored. They were graded into red,
marketable green, small green and culls. The culls were rotten or
deformed peppers of any color or size.
The Natural 11 plastic treatment yielded significantly higher than
almost all of the other plastic except the Natural 8, the research
team reported. The treatment that yielded significantly better than
the non-plastic plots were the Natural 9 and 10, Olive 19, Silver/Black
17 and Black 6,1,4,7 and 5. The plastics that did not yield significantly
higher than the check were Silver 14, Blue 13, White/Black 18 and
Black 3. The treatments that performed significantly poorer than the
non-plastic treatment were White 15 and 16.
An estimated total yield, if there was a second harvest, was made
by adding the weight of the small fruit multiplied by a factor of
2.5 to the yield of the first harvest. This did not result in any
significant yield changes between treatments.
The check treatment yielded the highest percentage of green fruits
and the lowest percentage of red fruits, but these differences were
not significant. This indicates that the use of most plastics resulted
in earliness of fruit maturity, the researchers said. The percentage
of culls was not affected by plastic treatments.
The average weight per fruit was not significantly different in the
small and green fruits, the team added. There was a significant difference
in the average weight of the red fruits between plastic treatments
but no specific color was best.
The Incentive Is There
So what were the conclusions of the study? Plastic mulch resulted
in significant yield increase and earlier production over non-treated
plots, Molinar and colleagues said. The best yield was in the Natural
11 treatment yielding 559 cartons per acre in one pick or 659 cartons
per acre in two picks over the non-plastic treatment.
One word of caution: It would only be economical to use this treatment,
the report stressed, if weeds were chemically controlled underneath
the natural plastics. Higher yields and earlier fruit maturity may
have occurred in the natural plastics if the weeds were chemically
treated early and/or there was no plant disturbance during hand weeding.
Otherwise, it would be more economical to use the Olive 19, Silver/Black
17 or Black 6 treatments. Weeds under the natural plastic were pulled
twice by hand reach through the planting holes. In the other plastic
colors it was difficult to see the weeds so only the weeds that came
through the holes were removed. The weeds were most aggressive in
the white plastic treatments.
Funding for these trials was provided by Ampacet Corp. to evaluate
the deterioration of the plastic in different areas of the world.
Plastic samples were collected from the treatment row ends of plots
that were left unplanted. Under the plastic treatments with no crop
there was little weed growth during the nine-month test period for
the three years of evaluation (three years for cantaloupe and one
year for bell peppers). Some weeds did germinate but died shortly
thereafter. Only in the white plastics did weeds grow more than several
inches before dying.
For more information on these trials, including the particular plastic
formulations, Contact Richard Molinar at rhmolinar@ucdavis.edu or
Brionna Barber at Ampacet (bbarber@ampacet.com)
