Empire State Fruit and Vegetable Expo Report
Plant Populations and Spacing: How Important Are They?
The Tomato Magazine
How important are pepper plant population per acre and plant spacing
on insect and disease incidence, effectiveness of pesticide applications
Mark A Bennett, a professor with the Department of Horticulture and Crop
Science, Ohio State University (OSU), reviewed recent research shedding
light on the question during the Empire State Fruit & Vegetable Expo
in Syracuse, N.Y. The tomato, pepper and eggplant session took place
Feb. 15 at the Oncenter Convention Center.
Bennett’s report was based on research done in collaboration with
Celeste Welty, Sally Miller, Richard Derksen, Salvador Vitanza and Elaine
Grassbaugh, all of OSU.
While there has been little research done recently in the Great Lakes
region to determine the most economically advantageous plant populations
for currently used pepper cultivars, Bennett summarized the following
key research points from other states:
Batal and Smittle (1981 – Georgia): These researchers compared
27,000, 40,000 and 60,000 bell pepper plants/ha (~11,250, 16,670 and
25,000 plants/acre). The biggest yield increase occurred when populations
were increased to 16,670 plants/A, but yields decreased when plant populations
were increased to 25,000 plants/A.
Locascio and Stall (1994-Florida): The two compared one, two and three
rows on two bed widths (48 and 72 inches wide) and in-row plant space
of nine and 12 inches between plants. Highest yields were from single
row orientation and wider in-row spacing. Best yields were achieved with
fewer plants/row. The number of rows per bed and the overall raised bed
width had more influence on yield than in-row spacing. Bell pepper fruit
yields per plant were also greater with the wider spaced in-row spacing.
Two rows per bed versus three rows resulted in non-significant yield
differences probably due to better light use. This is also confirmed
with the three-row orientation where plants in the middle row produced
the lowest yields compared to the outside rows on the same raised bed.
Stoffella and Bryan (1988-Florida): The team compared populations of
plug-mix seeded bell peppers planted at 21,500 to 258,000 plants/ha (9,000
to 107,000 plants/A). Variable in-row spacings of 13, 25, 38 and 50 cm
(5-20 inches) were compared. As plant population increased, shoot:root
rations generally declined. This suggests that the decrease in shoot
weight was greater than the decrease in root weight. At higher plant
populations, the larger root system to shoot mass is perhaps required
to improve water and nutrient absorption since root competition between
plants is higher. Marketable pepper fruit number and weight generally
decreased per plant and increased per hectare as plant populations increased.
Decoteau and Graham (1994-South Carolina): The researchers compared plant
spacing of cayenne pepper for mechanical harvesting. Plants were arranged
in single and double rows on raised beds at a plant spacing of 15 to
60 cm (6 to 24 inches) apart. As spacing increased from 15 to 60 cm,
the total fruit weight and number per plant increased linearly. As in-row
spacing increased, total fruit production per hectare decreased. In-row
spacing effected plant growth and fruit production. Closer plant spacing
generally produced more dry weight per plant, taller plants, thinner
stem diameters and fewer fruit set per plant but more plants per hectare.
Plants in double rows produced more fruit on the top of the plants compared
to single rows where more fruit developed lower on the plant. The double
row orientation may increase the probability of harvesting more fruit
Motsenbocker, et al., (1997 – Louisiana): The two evaluated the
effect of in-row spacing on two cultivars of machine-harvested jalapeno
peppers. Plants were spaced four, eight, 12 and 16 inches apart in-row.
Yields, in general, increased with reduced plant in-row spacing. This
effect, however, may be cultivar dependent. One cultivar, ‘Jalapeno-M,’ had
highest yields with four inches between plants vs. cultivar ‘TAM
Mild-1’ that obtained the highest yields with a
12-inch in-row spacing, but was not significantly different from the
four- or eight-inch spacing. Closer in-row spacing may provide increased
marketable yield of jalapeno peppers. Both cultivars had more plant lodging
with increased in-row spacings.
As for the Ohio situation, commercial practices vary from staggered twin
rows on raised beds with bed center five feet apart to single rows, three
to four feet apart, without raised beds, Bennett told the group. In-row
spacing ranges from 12 to 18 inches. Total populations range from 8,000
to 25,000 plants per acre.
“Hybrid pepper seed is expensive, particularly for processing peppers
where profitability margins are relatively slim,” the speaker said. “Growers
are seeking information to determine if plant populations can be adjusted
to reduce hybrid seed costs without significantly reducing yield, particularly
if this is associated with better insect and disease control and thus
Plant spacing affects the microclimate in the plant canopy that, in turn,
may influence the incidence and severity of a number of diseases as well
as the attractiveness for egg laying by European corn borer, Bennett
said. No data are available on the effect of plant density on the epidemiology
of anthracnose (C. acutatum) on peppers. However, plant spacing and microclimate
are known to affect the severity of anthracnose disease on other crops
(Boudreau and Madden 1995; Koech and Whitbread 2000).
In a 2005 field study near Fremont, Ohio, single-row pepper plots with
10,500 to 14,000 plants/A equivalent provided the best pepper yields
and quality in general, Bennett said.
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