Row Cover & Population Density Effects on Yield of Bell Peppers in South Coastal British Columbia; Gardening Guidebook

8/9/2019 Row Cover & Population Density Effects on Yield of Bell Peppers in South Coastal British Columbia; Gardening Guidebook

1/9

Row

cover and

population

density

effects

on

yield

of

bell

peppers

in south

coastal

British

Columbia

M.

M. Gaye1,

P. A.

Jolliffe2,

and

A.

R.

Maurer3

I

Cloverdale

Soil Conservation

Group,

17720-57th

Ave., Surrey,

British

Columbia,

Canada

VJS

4P9;2

Department of Plant

Science, 'tJniversity

of

British

Columbia,

Vancouver,

British

Columbia,

Caiada

V6T 124;

and3Agriculture

Canada

Research

Station,

Agassiz,

British

columbia, canadav)M

1A0. Received

26

April

1991,

accepted

ZS

March 1992.

Gaye,

M.

M.,

Jolliffe,

P.

A.

and

Maurer,

A.

R. 1992.

Rolv cover

and

population density

effects

on

yield

of bell

peppers

in south

coastal

British

Columbia.

Can.

J.

Plant Sci.

72: 901-909.

Row

covLr and

plant

population

density

effects

were

studied

at the Agriculture

Canada

Research

Station,

Agassiz,

gC

in tgSS

and 1989.

Bell

pepper

plants

(Ace

Hybrid)

were transplanted

into twin

rows

(0.45

m

upi.t)onraisedbeds(1.8-mcenters)atfivepopulationdensitiesof

1.39,

1.85,2.78,5.56and

lf

i

plant

*

'.

Fo.7

wk in 1988 or 8

wk in 1989,

iubplots

were either

covered

or not

covered

with

slit

clear

polyethylene

tunnels.

A nonlinear

regression

model

was used to define

yield-population density

responses.

Row

covers enhanced

early

and

overall

yiekis

in

1988 and

overall

yield

in

1989. Vegetative

and

reproductive

yields

(kg

plani-r;

declined

with

increasing

plant population

density.

Yields

were.directf

reiated to

population

density

when

measured

on

a

land-area

basis.

Maximum

fruit

yield

(7.9

kg

m

')

was obtained at the highest

population density.

Treatment

influences

on

fiuit size

were small

and

did

not affect horticulturafqualiiy.

An economic

analysis

showed

that

net

returns

were

greatest

with

plants

grown

under row covers

at the highest

population density.

Key

words:

capsicum

annuum

L.,

field

bell

peppers,

population

density,

row covers

Gaye,

M. M.,

Jolliffe,

P. A.

et Maurer,

A.

R. 1992.

Effets d'une

couverture

plastique

et

de la den-

siti de

peuplement

sur

le rendement

du

piment

cloche

dans

la

zone c0tibre

du

sud

de

la

Colombie-

Britanniqul. Can. J.

Plant

Sci.

72:901-909.

Les

effets de

la couverture

plastique

et

de

la densit6

de

peuplement ont

6t6

6tudi6s

ir

la

station f6d6rale

de

recherches

agronomiques

d'Agassiz

(C.-B.)

en

t988 et

1989. Des

plants

de

piment cloche

(Ace

hybrid)

ont

6t6

repiqu6s

sur billons

(1,8

m centre

it

centre) en

lignes

jumel6es

(6iarteement

de

0,45

m), d 5

densit6s

de

peuplement

:

1,39, 1,85'

2,78'

5,56 et

1l,l

plantes

au

mbtre carr6.

Pendant

7 semaines

en

1988 et

huit semaines

en 1989,

des sous-

parcelles

dtaient soit

recouvertes

ou non

recouvertes

de

mini-tunnels

de

poly6thylene

transparenf

per-

ior6.

Un

modble

de

r6gression

non lin6aire

a 6t6

utilis6

pour

d6finer

les r6ponses

rendement-densit6

de

peuplement.

Les

mini-tunnels ont

augment6

le

rendement

pr6coce et

le rendement

total

en 1988

ainii

que

le rendement

total

en

1989.

L; rendement

v6g6tatiftet

fruitier

(kg

plante

r;

diminuait

en

proportion

de

I'accroissement

de la densit6.

Calculd

par unit6 de

surface,

le rendement

6tait

directe-

ment

li6

)r la

densit6.

Le rendement

le

plus

6lev6

(7,9

kg

-

';

6tait

obtenu

ir la densit6

la

plus

fofte.

Les

traitements

n'avaient

que

peu

d'effet

sur

le

calibre

des

fruits

et

n'influaient

pas

sur

leur

qualit6

horticole.

L'analyse 6conomique

a d6montr6

que

les

recettes

nettes

les

plus fortes

etaient obtenues

en

culture sous

mini-tunnel

d la

plus forte densit6

de

peuplement.

Mots cl6s: Capsicum

annuum L.,

piment

cloche

de

plein

champ,

densit6

de

peuplement,

mini-tunnel

plasrlque

Can.

J.

Plant Sci.

72: 90f-909

(July

f992)

901

p

y


2/9

902

CANADIAN

JOURNAL

OF PLANT SCIENCE

Field

production

of

bell

peppers

(Capsicum

annuum

L.) in

south

coastal British

Columbia

is

limited

because

of

the restricted

number

of

degree

days

above

10'C from

April

to

Sep-

tember

(851

degree

days)

(Environment

Canada

1982).

Transplants

are

used in

com-

mercial

production

to

promote

early

fruit

har-

vesting

and improve yields.

Row

covers

can also

be

used to

enhance

bell

pepper

fruit yield (Mohd

Khir

et al.

1981),

but

few Fraser

Valley

producers

have

adopted

this technique

because

of

the additional

costs.

Row

covers

could

become

economically

viable

if more productive

cropping

systems

were

developed.

Fraser

Valley

producers

cur-

rently plant

bell peppers,

such

as

Ace

Hybrid,

at

a within-row

spacing

of

0.30-0.40

m and

0.75-0.90

m between

rows

(British

Columbia

Ministry

of

Agriculture

and

Fisheries

(BCMAF)

1989).

These

recommendations

are

based

on

traditional

practices,

as

population

density

studies

have

not

been conducted

in

British

Columbia

(M.

Sweeney

1990,

BCMAFF,

personal

communication).

In

other

regions,

increasing

plant

population

density

has

resulted

in

greater

yields

of bell pepper

fruit

(Porter

and

Etzel

1982:

Ahmed

1984).

High population

densities

have

not

affected

fruit

size

(Stoffella

and Bryan

1988),

but

might

not

cause

yield

improvement

because

of

asymptotic

(Batal

and

Smittle

l98l)

or

parabolic

(Holliday

1960)

yield

density

responses.

Most row

cover

or

population

density

studies

of bell peppers

have

reported

fruit

yields

and

have not

considered

the

responses

of

vegetative

plant

components.

Monoculture

yield

density

responses

are

successfully

described

by reciprocal

equations

(Willey

and

Heath

1969),

such

as

Bleasdale's

0967)

model.

The

objectives

of our

studies were to

determine

the

effects

of row

covers

and plant

population

density

on

vegetative

and

reproductive

yields

of

bell

peppers

grown

in

south

coastal

Bntish

Columbia,

and to

deter-

mine

the economic

viability

of

the treatments.

MATERIALS

AND

METHODS

Studies

were

conducred

in

1988

and

1989 at the

Agriculture

Canada

Research

Station,

Agassiz,

British

Columbia.

Seven-week-old

bell

pepper

plants

(Ace

Hybrid,

Stokes

Seeds Ltd.,

Sr.

Catharines,

ON)

were

transplanted on

l2

May

in

both

years,

onto raised

beds mulched

with

black

polyethylene (thickness

28

pm).

The raised

beds

were

0.23

m

high, 1.1m

wide and

1.8 m

centre-to-centre.

The plants

were

transplanted

into

twin

rows

with

a

0.5-m

between-row

spacing. The

soil

(Rego

Humic

Gleysol,

pH

6.2)

had

been

prepared

in 1988 with

a

broadcast-

incorporated

application

of

165

N,

165 P2O5,

165 K2O

and 4.5 B

(kg

ha-',

respectively)

and with

23

t ha-' cattle manure.

In 1989,

the fertilizer

was

applied through

a trickle

irrigation

system

located under

the

plastic

surface

mulch.

The

experimental

design was

a split-plot with

four replications.

Main plots

were uncovered

or

were

covered

with slit

clear

polyethylene

tunnels

(thickness

50

pm).

Five

population

densities, 1.39,

1.85,

2.78,5.56

and

11.1plant

m-'

lcor-

responding

to

within-row

spacings of 0.8,0.6,

0.4,

0.2 and 0.1 m, respectively)

formed

the subplots.

Each

subplot consisted

of eight

plants;

the

plants

at the

end of

each row

were guards.

Row

covers

were

applied to

the

appropriate

treatments

immedi-

ately following

transplanting,

and

were removed

on

7 July 1988 and

14 July 1989.

Irrigation

(over-

head in

1988

and trickle in

1989) and

pesticides

(

ior

aphids)

were

applied as

necessary

throughout

the

growing

seasons.

Fruit

were

harvested

at the mature green

stage,

twice

a

week

from

3

Aug.

1988

and 19

July

1989,

until 21

Sept.

in

both

years.

The

harvested

fruit

were

graded

as marketable

(=

80

g

and

free

from

disease and insect

damage),

undersized

(

< 80

g)

,

or cull

(diseased

or insect

damaged),

and the

weight,

width

and length were recorded.

Fruit from

the initial

28 d of harvest were

considered

early

and

"overall

fruit

yield"

was rhe cumulative

yield

over the

entire harvest

period.

Two randomly

selected

plants

from each

plot

were

destructively harvested

on27 and 28

Sept.

1988. Plants

were removed

from the soil.

and the

roots

washed to remove

soil

particles.

Plant com-

ponents

(leaves,

stem

and

petioles,

and

roots)

were

oven-dried

to a constant

mass

at 70"C, and

the dry

masses

were recorded.

Air

temperatures

were monitored

30 cm above

the soil

surface with

thermisror

probes

(107,

Camp-

bell

Scientific, Logan,

UT)

and

a datalogging

microprocessor (21X,

Campbell

Scientific).

Daily

minimum

and maximum

temperatures and mean

hourly

temperatures,

each based

on readings

made

every 10 min, were

computed.

p

y


3/9

GAYE

ET

AL,

ROW COVER

AND

DENSITY

EFFECTS

ON BELL

PEPPERS

0.75

903

1.00

c\i

o

E

o)

J

Fj

T

l.,J

=

z

)

o_

trl

aF

-F

--u

(9

tJ

0.15

c')

Fj

-

Lr.,l

=

z

J

o_

LrJ

=

TJ

t

0.

r0

0.05

u.1f,

0.00

0.00

POPULATION

DENSITY,

Plonfs

m-'

Fig. 1.

Means and

nonlinear regressions

of 1988

vegetative

plant

dry

weight

on

population

density

for

uncovered.

-,(v

rEI

:

8.37

+ 17.1X,

RSS

:

0.025,

EMS

:

0.0007)'

and

covered,

-----

0

262

-

-95:7

+ 1r6X,

RSS

:

0.039,

EMS

:

0.001);

treatments

on

a

per plant basis and

con-

verted

to a land area basis.

RSS and

EMS denote

residual

sum

of squares

and error

mean

square,

resDectivelv.

Statistical

Analysis

Variables were

subjected

to the

analysis of

vari-

ance

[GLM

procedure

of Statistical

Analysis

System

(SAS),

SAS

Institute

19851, to determine

main treatment effects and

interactions.

Data from

both

years

were combined

for

analysis,

and tested

separately

when results showed statistical

differ-

ences between

years.

Yield-plant

population

den-

sity responses in 1988 were defined

using

a non-

linear regression

procedure

IBMDPAR

(Dixon

1985)l according to a

model ofBleasdale

(1967):

y":d+px

where

,y

represents mean

yield

plant-l and

1

represents

plant population

density.

Parameter

o

is

an

index of

plant

yield

in the absence

of compe-

tition, and

B

is an index of the

responsiveness

of

a

plant

to

population

density

changes.

Parameter

0 is thought to be

related to the utilization

of

environmental

resources in the space

accessible to

a

plant

tWatkinson

1984).

05c

Economic

Analysis

Net economic

costs and

returns

of

each

treatment

were compared

to

a

population

density

of 2.'78

plants m

',

without

row covers.

This density

most closely

corresponds

to

the

current

commer-

cial

planting density

in

British Columbia.

Trans-

planting costs

were

based

on

machine

harvesting

and included

machinery

operation,

depreciation,

interest on the

investment,

and

labour

(M.

Sweeney

1991,

BCMAFF,

personal communication).

Returns

were

based

on

the

landed

costs

of

green

peppers to

wholesalers

in

Vancouver, BC

in

1988

and

1989

(J.

Atcock

1991,

BCMAFF,

personal

communication).

RESULTS

Air

Temperatures

Ambient temperafures

were

generally

warmer

in

July

and August

of

1988 than

in 1989

(data

not

presented).

Row covers

elevated

daily

mean air temperature

as

much

as

4oC

above

p

y


4/9

904

CANADIAN

JOURNAL

OF

PLANT

SCIENCE

uncovered

trgatments.

Daily

mcan

tempera-

ture

under

the row

covers

was

never

greater

than

27"C

in

1988

and

29"C in

l989]Mean

daily

maximum

temperatures

for rhe

3-d

period

following

transplanting

in

1988 were

23'C

and

35'C

for

uncovered

and

covered

plots,

and

29'C

and

39"C,

respectively,

in

1989.

Also.

maximum

air

temperature

under

the row

covers

was greater

than 40"C

on

19 d

in

1988

and

I

I

d

in

1989.

Vegetative

Dry

Matter

Yield

The

application

of row

covers,

and

interac-

tions

between

row

covers

and plant

popula-

tion

density,

did not

influence

vegetative plant

components.

The

yield

of plant

components

decreased

linearly

with

increasing

population

density

(data

not presented).

Total vegetative

yield,

but

not the

yields

of

vegetative plant

components,

were

satisfactorily

fit

to Bleas-

dale's

model.

Vegetative

yield

decreased

in

response

to

increasing

population

density

When

measured

on

a

per-plant

basis,

but

increased

on

a

per-land-area

basis

(Fig.

l).

Fruit

Yield

FRUIT

CHARACTERISTICS

AND

UNMAR-

KETABLE

FRUIT.

Fruit

size

{g fruit

l;

was

larger

in

1988

than

1989

(124

and

109 g,

respectively).

Fruit

iength,

over

all

treatments,

was

9.7

and

10.0 in

1988

and 1989.

resDec-

tively:

mean

fruit width

was

7.5 in

1988

and

7.0

in

1989.

Treatment

effects

on fruit

size

and

shape,

when

detected,

were

small

and not of

horticultural

significance

(data

not presented).

Satisfactory

fits

to

nonlinear

models

were

not

obtained

for

unmarketable

fruit:

hence.

ANOVA

results

are

presented

(Table

l). The

percentage

of marketable

fruit

was

higher

in

1988

than

1989

(80

and

58%. respeciively).

but

was generally

not

affected

by

treatments.

The

exception

was

a

significant

linear

trend

in

1988

showing

a decrease

in

the

percentage

of

marketable

fruit with

increasing

population

density.

The

yield

of undersized

fruit was

greater

in

1989

than

1988,

but the quanrity

of

diseased

fruit

did not

differ

between

the

years.

EnnIyFRUITYIELD.

Row covers

enhanced

early marketable

fruit

yield

and

total early

fruit

yield

in 1988 but not in

1989

(Table

l).

These results

were

probably

due

to

the

high

temperatures

that

followed

transplanting

in

1989.

Many

plants

were

stressed

and showed

symptoms

of sunscald.

In

1988 early mar-

ketable fruit

yield

was

90%

greater

from

covered

than

uncovered treatments.

The

curves

shown in

Fig. 2

represent

the

best fit

of

the

regression

equation for

1988 early mar-

ketable yield.

Early

yield

per

land

area

increased

in

response

to increasing population

density in 1988 and

1989.

In

1988,

a signifi-

cant

row-cover-by-population-density

interac-

tion

indicated that

row

covers had

a

greater

influence on

early

yield

at low

population

den-

sities

than

at high

densities.

In

both

years,

early

yield per

land

area increased in response

to

increasing population

density. 1989

early

yield

data showed

extreme

variability

between

plants

and

satisfactory

fits to nonlinear

models

were not

obtained.

Ovenelr- FRUIT

yrELD.

In

both

years,

row

covers

enhanced overall

marketable

fruit

yield

(Table

1).

Fruit

yield

per plant

decreased and

yield

per

land

area increased, in response

to


density

(Fig.

3). A sig-

nificant

interaction

showed

that the

influence

of

row

covers

on marketable

yield

per plant

declined

with

increasing

population

density.

Interactions

on a

per-land-area

basis were not

significant.

Economic

Analysis

The

application of row

covers increased net

costs

above

the

current industry

population

density

standard

(2.78

plants

m-')

at all

population

densities

(Table

2).

Planting

at

the

highest

population

density tested. I l.l

plant

m

'.

increased

net

costs by

$5741

ha

I

without

row covers

and by 57795

ha-l

with

row

covers.

Net economic

returns

increased with


densities

higher

than the

standard, but returns were

greatest

with

the

addition

of row covers.

Row

covers

also

increased

returns when

used at the industry

standard. The

largest net

economic return,

$19815

ha

'

above

the standard, was

obtained

from

covered

plants grown

at the

p

y


5/9

905

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6/9

906

CANADIAN JOURNAL

OF

PLANT

SCIENCE

0369t2036912

POPULATION DINSITY,

plonts

m-'

Fig.

2. Means

and nonlinear

reg_r-essions

of 1988

early

marketable fresh ftuit

yield

on

population

den-

sity

for

uncovered,

-

(l-uuror

:

t.0 + 0.00293X, RSS

:

6.7,

EMS

:

0.087), and covered,

----- (i

r56

:

-0.23

+

0.438X,

RSS

:

18.3, EMS

:

0.23'7); rreatments on a

per-plant

basis and

converted

to a land-area

basis.

RSS

and EMS

denote

residual

sum of squares

and

error

mean

square,

respectively.

6.0

N

|

4.5

C

L

f

Documents

Row Cover & Population Density Effects on Yield of Bell Peppers in South Coastal British Columbia; Gardening Guidebook