Soil and Crop Management
Aug. 2009
SCM-27
Benefits and Costs of Using Perennial Peanut
as Living Mulch for Fruit Trees in Hawai‘i
Ted Radovich,1 Linda J. Cox,2 Jari Sugano,3 and Travis Idol2
Departments of 1Tropical Plant and Soil Sciences, 2Natural Resources and Environmental Management,
and 3Plant and Environmental Protection Sciences
P
erennial ground covers can be grown under fruit
trees as living mulch, a management strategy that
is expected to improve soil quality, reduce the need for
chemical inputs, and improve the sustainability of tropical fruit orchards (Hensley et al. 1997, Mullahey et al.
1994, Shen and Chu 2004). Its ability to fix atmospheric
nitrogen, produce dense cover with little maintenance,
and protect soil from erosion has resulted in wide use of
perennial peanut throughout Hawai‘i as a living mulch
in perennial cropping systems (Figure 1, CTAHR 2009).
Although two species of perennial peanut, Arachis glabrata and A. pintoi, are used as goundcovers worldwide,
the stoloniferous A. pintoi (Krap. and Greg.) is most
commonly used in Hawai‘i.
To help Hawai‘i growers make management decisions
about the use of a living mulch, this publication describes
experiments conducted to study the effects of perennial
peanut planting method and density on (1) groundcover
canopy development, (2) selected indicators of soil
quality, (3) fruit tree nutrient status, and (4) the cost of
establishing the living mulch.
In orchard systems, perennial peanut is commonly established using seeds or cuttings, while rooted plants may
be used for smaller-scale plantings. The recommended
spacing for cuttings or drilled seed is 1 x 1 ft, although
wider spacing of 1 x 3 ft is frequently used because the
labor to prepare cuttings and plant the material is costly
(Figure 2). Rates recommended for broadcast seed range
from 17 to 43 lb/acre (Glover 1994, Hensely et. al. 1997).
Unrooted cuttings are often used to avoid paying the seed
cost of $15.00/lb. Cuttings require preparation and hand
planting, are less able to tolerate adverse conditions during establishment, and may be slower to establish than
seedlings (Kerridge and Hardy 1994, Mitschele 2007).
Seeding at 40 lb/acre or more is expected to improve
the rate of cover establishment in Hawai‘i (Clement and
DeFrank 1998, Hensley et al. 1997). However, replicated
trials have not confirmed this, nor they have confirmed
differences in the rates of establishment between seeded
and transplanted peanut.
Fruit tree growers who use A. pintoi as a living mulch
report improved tree growth and reduced reliance
on fertilizers three or more years after establishment
(CTAHR 2009). Clement and DeFrank (1998) observed
lower growth of peach palm (Bactris gasipaes) with a
perennial peanut cover than with weed mat during the
first 18 months, but the yield differences had ceased to
be significant in measurements taken 24 and 30 months
after planting. The authors suggested that the initial yield
differences were due to N competition, but plant tissue
and soil nutrient levels were not reported. Little information is available about the contribution of perennial
peanut to soil physical, chemical, and biological quality
during the critical period of fruit tree establishment.
Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i 96822.
An equal opportunity/affirmative action institution providing programs and services to the people of Hawai‘i without regard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or status as a covered veteran. CTAHR publications can be found on the Web site <http://www.ctahr.hawaii.edu/freepubs>.
UH–CTAHR
Benefits and Costs of Using Perennial Peanut as Living Mulch
SCM-27 — Aug. 2009
The experimental set-up
Planting
and management
contribution
of perennial peanut to
soil physical, chemical and biological quality during the critical
Experimental plots were esperiod of
tree establishment.
tablished
at fruit
the University
of
Hawai‘i Research
Stations
Hawai’i growers atcould make better management decisions in the long-run if they knew more
Poamoho (Lat. 21°32’58” N
about158°05’47”
how perennial
peanut planting material and density affects peanut establishment, soil quality and
Long.
W, elevation
459
ft) andstatus
Waimānalo
nutrient
of fruit(Lat.
trees. This paper presents the effect of planting method and density on: 1) peanut
21°20’41” N, Long. 157°44’31”
canopy
development;
2) select indicators of soil quality, 3) fruit tree nutrient status, and 4) the cost of
W,
elevation
60 ft). Climate
and soil characteristics of
mulch establishment.
the two sites are presented in
Tables 1–3.
Two trees of three fruit species were planted in plots 120
ft long x 12 ft wide on October
10, 2007 at Waimānalo and
October 17, 2007 at Poamoho.
Grass strips 6 ft wide were
maintained between the plots.
Figure 1. Two-year-old perennial peanut cover established in an O‘ahu orchard.
The tree species were guava
‘Ruby x Supreme’ (Psidium
The mulch treatments were (1) black woven weed mat,
guajava), sapodilla ‘Alano’ (Manilkara zapota), and
(2) perennial
peanut seeded at 54 lb/acre, (3) perennial
mountain
apple
‘White’
(Syzygium
malaccense).
Trees
Figure 1. Two year-old peanut
Figure 2. Peanut establishing from
peanut
seeded
at 18 lb/acre, and (4) stolons planted at low
were spaced
15
ft
apart
within
the
plots
and
the
planting
established in an O’ahu orchard
stolon cuttings.
density. The seeding was done on November 9, 2007 at
holes were approximately 1 ft wide by 1.5 ft deep. The
Waimānalo and November 16, 2007 at Poamoho. Seed of
fruit
trees were
fertilized
with 2 lb of bone/blood meal
Materials
and
Methods
cv. CIAT-17434 was purchased from a local vendor and
incorporated in the planting hole at transplanting and
Planting &
Management
drilled 9 inches apart within rows and 1 or 3 ft between
topdressed
with
2.5 lb of compost approximately three
rows at 54
18 pounds
per acre,
respectively.
Seed
months after
transplanting.
Analyses
of the bone at
meal
Experimental
plots
were established
the University
of and
Hawaii
Experiment
stations
at Poamoho
was not inoculated before planting. Black weed mat was
and compost are presented in Table 4.
o
o
o
32’58”
N Long
158
05’47”inW,
elevation 459 applied
ft) and at
Waimanalo
(Latas21planting
20’41”occurred.
N, LongStolons
the same time
mulch
treatments
were
arranged
a randomized
(Lat
Four21
of A. pintoi ‘Golden Glory’, obtained from a local farm,
complete
block design with three plots per treatment.
o
157 44’31” W, elevation 60 ft). Climate and soil characteristics of the two sites are presented in Tables
1-3.
Table
temperature
experimental
Table1.
1.Average
Average monthly
monthly temperature
at at
thethe
experimental
sites in
in 2007
2007 and
sites
and2008.
2008.
Month
January
February
March
April
May
June
July
August
September
October
November
December
2007
Waimanalo
Poamoho
74
72
73.5
74.2
76.7
78.8
79
79.8
79.7
-75.6
73.9
71.2
70.2
71.8
71.9
75.1
77.3
78.2
78.9
78.2
76.6
73.4
72.6
2008
Waimanalo
Poamoho
71.8
72.1
74.5
74.3
76.7
77.9
79.5
79.8
79.2
78
76.2
--
69
70.1
73
72.2
74.8
76.5
77.5
77.7
77.1
76.1
74.3
72.4
Table
2.2.Total
rainfallatat
the
experimental
Table
Totalmonthly
monthly rainfall
the
experimental
sites sites
in
2007 and
in 2007
and2008.
2008.
Month
January
February
March
April
May
June
July
August
September
October
November
December
2007
Waimanalo
Poamoho
3.19
2.22
4.18
2.51
0.88
0.82
2.59
0.93
1.55
-15.12
14.54
4.85
1.88
3.08
1.48
0.59
0.49
0.33
3.28
0.48
0.59
7.23
10.94
2008
Waimanalo
Poamoho
1.9
0.94
0.14
4.15
1.52
2.32
2.71
1.58
2.69
3.2
4.57
--
1.79
5.59
0.39
2.59
0.92
0.4
1.44
0.71
0.62
1.65
4.49
18
2 Table 3. Chemical analysis of soil from the Waimanalo and Poamoho experimental sites. Each value is a mean of 12 analyses.
Location
Waimanalo
Soil Order
Mollisol
pH
6.5
%
C
2.2
<------------------------- mg/g -------------------- >
P
K
Ca
Mg
306
1098
3695
2315
3
<---------------------- mg/dm -------------- >
Mn
Fe
Cu
Zn
170
67
8
7
Hawai’i growers could make better management decisions in the long-run if they knew more
about how perennial peanut planting material and density affects peanut establishment, soil quality and
nutrient status of fruit trees. This paper presents the effect of planting method and density on: 1) peanut
UH–CTAHR
and Costsofofsoil
Using
Perennial
as Living
Mulch
Aug.of2009
Benefits
SCM-27
canopy
development; 2) select
indicators
quality,
3) Peanut
fruit tree
nutrient
status, and
4) the—cost
mulch establishment.
micro emitters placed on risers
2 ft above ground in between
trees within rows. To control
weeds, plots were sprayed with
glyphosate before planting and
were weeded by hand every
6–8 weeks.
Soil quality
Six-inch soil cores were taken
at three locations within treatment plots before planting
Figure 1. Two year-old peanut
Figure 2. Peanut establishing
from after planting.
and 7 months
established in an O’ahu orchard
stolon cuttings.
Soil solution was collected 12
months after planting from
Materials and Methods
suction cup lysimeters installed
to an 8-inch depth. Chemical
Planting & Management
analyses were conducted as
Experimental plots were established at the University of Hawaii Experiment
stations
at Poamoho
described
in Mitschele
(2007).
o
o
o
respiration,
volumetric
(Lat 21 32’58” N Long 158 05’47” W, elevation 459 ft) and Waimanalo (Lat 21 Soil
20’41”
N, Long
moisture content, and temperao 2. Peanut establishing from stolon cuttings in a weathered soil (Oxisol) on O‘ahu.
Figure
157
44’31” W, elevation 60 ft). Climate and soil characteristics of the two sites
are
presented
in12
Tables
ture
were
measured
months
after peanut establishment.
1-3.
Soil respiration was measured using a CIRAS-1 Gas
were planted in rows 3 ft apart, with 9 inches between
Table
1. Average
monthly
the experimental
Table 2. Total
at the experimental
sites
in
Analyzer
andmonthly
SRC-1 rainfall
Soil Respiration
Chamber.
Abovestolons
within rows,
fortemperature
a density ofatapproximately
14,500
sites in 2007 and 2008.
2007 and 2008.
ground
biomass was removed with minimal soil disturstolons/acre. Cuttings approximately 6 inches long with
2007
2007
2008
bance,
and the
chamber
was placedWaimanalo
on the2008
soil
surface,
several nodes
and at
least
one prominent
bud
or sprout
Month
Waimanalo
Poamoho
Poamoho
Month
Waimanalo
Poamoho
Waimanalo
Poamoho
measuring
the
rate
of
increase
for
the
CO
concentration
were
prepared
from
older
stolons.
Most
of
the
leaves
were
January
3.19
4.85
1.9
1.79
January
74
71.2
71.8
69
2
February
2.22 Moisture
1.88 content 0.94
5.59 at a
February
70.2and at least
72.1 three-fourths
70.1
inside
the chamber.
was measured
removed from 72
the cuttings
of
March
4.18
3.08
0.14
0.39
March
73.5
71.8
74.5
73
4-inch
depth using
reflectometry
(TDR)
on
the cutting was74.2buried in71.9
the ground.
April
2.51 time domain
1.48
4.15
2.59
April
74.3
72.2
0.88
0.59
1.52
0.92
May
76.7 irrigated
75.1with individual
76.7
74.8
aMay
Field
Scout
TDR
meter.
Soil
temperature
was
measured
The trees were
emitters
at 5
June
0.82
0.49
2.32
0.4
June
78.8
77.3
77.9
76.5
atJuly
a 4-inch depth
using a digital
thermometer.
2.59
0.33
2.71
1.44
gal/hr for three79hours three
and the
July
78.2days a week,
79.5
77.5peanut
August
0.93
3.28
1.58
0.71
August
79.8
77.7
was irrigated at
the same78.9
frequency79.8
and duration
using
September
1.55
0.48
2.69
0.62
September
79.7
78.2
79.2
77.1
October
November
December
-75.6
73.9
76.6
73.4
72.6
78
76.2
--
October
November
December
76.1
74.3
72.4
-15.12
14.54
0.59
7.23
10.94
Table 3. Chemical analysis of soil from the Waimānalo and Poamoho Research Station sites.
Each value is a mean of 12 analyses.
3.2
4.57
--
1.65
4.49
18
Table 3. Chemical analysis of soil from the Waimanalo and Poamoho experimental sites. Each value is a mean of 12 analyses.
Location
Waimanalo
Poamoho
Soil Order
Mollisol
Oxisol
%
C
2.2
1.4
pH
6.5
7.0
<------------------------- mg/g -------------------- >
P
K
Ca
Mg
306
1098
3695
2315
522
601
1840
308
<---------------------- mg/dm
Mn
Fe
170
67
159
5
3
-------------- >
Cu
Zn
8
7
9
9
Table
4. Analysis
of bone
compost
used to fertilize
fruit
trees. fruit trees.
Table
4. Analysis
of meal
boneand
meal
and compost
used to
fertilize
Bone meal
Compost
--------------------------------%---------------------N
C
P
K
Ca Mg
Na
9.19 46.00 1.71 0.60 3.18 0.13 0.50
1.11
17.63
0.34
0.84
7.48
1.08
0.31
---------------ug/g-------------Fe
Zn
Cu
B
481
55
6
1
-782
268
101
3
Two trees of three fruit species were planted in plots 120 ft long x 12 ft wide on October 10,
UH–CTAHR
Benefits and Costs of Using Perennial Peanut as Living Mulch
SCM-27 — Aug. 2009
Perennial peanut establishment at the Poamoho and
Waimānalo sites was measured periodically using a
2.70-ft2 (0.25-m2) quadrant to determine canopy ground
cover at three locations within each plot. Tree height and
trunk diameter were measured periodically for the first
7 months of establishment. At 7 months after planting,
the third expanded leaf pair of sapodilla and guava from
both locations was analyzed for nutrient content. Weed
biomass was measured 7 months after planting in the
Waimānalo plots. Peanut and weed biomass was also
determined 12 months after peanut establishment at the
same location.
The experiment’s results
Perennial peanut establishment
Peanut canopy establishment was most rapid in the plots
seeded at 54 lb/acre, with 75–100 percent coverage within
8 months, followed by the lower seeding rate and the
stolon plots, with 25–60 percent coverage in the same
period (Figure 3). Canopy development was quicker at
Waimānalo than it was at Poamoho, which may reflect
Waimānalo’s higher temperatures, rainfall, and native
soil fertility (Tables 1–3). Twelve months after planting,
the peanut treatments were similar in canopy cover at
each location, although peanut covered 100 percent of
the ground at Waimānalo and only about 70 percent at
Poamoho. Greenhouse trials indicated that rhizobial
inoculation would have reduced the difference in peanut
establishment between the two locations.
Rapid canopy establishment minimizes weeding
costs (Hensley et al. 1997). Seven months after planting,
the weed biomass was similar between the low seeding
rate and stolon treatments, at 0.28 and 0.27 pounds/ft2,
respectively, and lowest at 0.20 pounds/ft2 in the 54 lb/
acre seeding rate. All treatments approached 100 percent
cover at the Waimānalo station, with peanut biomass being
significantly greater at the highest seeding rate and weed
biomass being greatest for the stolon treatment (Figure 4).
Soil quality and characteristics
Soil quality is defined by its ability to support ecological
processes that promote plant growth (Magdoff and Weil
2005). These processes include water and nutrient retention, nutrient cycling, disease suppression, etc. Physical
and chemical characteristics of the station soils before
and 7 months after planting are presented in Tables 5 and
4
Canopy cover development (% of total ground cover)
Perennial peanut and fruit tree establishment
Figure 3. Peanut canopy cover development as a
percent of total ground cover. Each value is a mean of six
observations.
6. The effect of peanut mulch on soil chemical characteristics was not different from the weed mat, with the
exception of potassium, which was significantly lower
in the peanut treatments. Because 7 months may have
been too short a time to detect differences in soil quality,
additional soil measurements were postponed until 12
months after planting. Significant differences were then
observed in soil solution nitrate concentrations and soil
CO2 evolution between the peanut treatments and the
black weed mat treatment at both locations (Figures 5
and 6).
Soil respiration is a sensitive measure of its biological
activity. Soil respiration values in all peanut treatments
UH–CTAHR
Benefits and Costs of Using Perennial Peanut as Living Mulch
0.8
SCM-27 — Aug. 2009
25
Weed
CO2 (mmol/m2 /sec)
)
a
20
-1
0.6
Seed-54
Seed-18
Stolon
Mat
aa
a
sec 15
b
CO2
0.4
10
mol m
(µ
5
0.2
0
0.0
4
8
d-5 eed-1
See
S
St o
l on
5
Peanut
b
Waimānalo
Waimanalo
b
c
Poamoho
Poamoho
Figure 5. Soil respiration under mulch treatments at
Waimānalo and Poamoho 12 months after planting. Bars
are means of 9 values. Means within locations with different
letters are significantly different at the 5% level.
4
35
3
2
Soil solution nitrate (mg/g)
2
Above-ground biomass (kg·m )
-2
)
-1
1
0
4
8
d-5 eed-1
See
S
lo
Sto
n
Figure 4. Peanut and weed biomass (fresh weight) at the
Waimānalo station 12 months after peanut planting. Each
value is a mean of 3 observations.
were two to four times larger compared to the black weed
mat treatments. Respiration values observed under peanut
were similar to those reported for forest soils in Hawai‘i
and elsewhere (Giardina et al. 2004, Jassel et al. 2004). In
contrast, nitrate-N levels in soil solution were generally
lower under peanut than weed mat treatments (Figure
6), which may reflect competition for N from both the
peanut and soil microbial populations. Soil temperatures
were also reduced for the peanut treatments compared
to weed mat treatments (Figure 7), while moisture levels
under peanut were higher than under weed mat (Figure
8). Higher moisture levels may have contributed to increased microbial activity under peanut.
30
25
Seed-53
Seed-18
Stolon
Mat
20
15
(mg g
10
Soil solution
5 nitrate
0
Waimānalo
Waimanalo
Poamoho
Poamoho
Figure 6. Soil solution nitrate levels under mulch
treatments at Waimānalo and Poamoho 12 months after
planting. Values are means of 6 values. Error bars are mean
standard errors.
Fruit tree growth
Fruit tree growth was variable, and no significant differences among treatments in trunk diameter or tree
height were detected. However, tissue nitrogen content
was lower under perennial peanut treatments compared
to trees grown with the weed mat, and only trees in the
weed mat treatment had tissue nitrogen levels within
the critical range established for guava (Figure 9). Other
nutrients differed little among treatments (Table 7).
5
peanuttreatments.
treatments.Since
Sinceseven
sevenmonths
monthsmay
mayhave
havebeen
beentoo
tooshort
shorta atime
timetotodetect
detectdifferences
differencesininsoil
soil
peanut
quality,additional
additionalsoil
soilmeasures
measureswere
werepostponed
postponeduntil
until12
12months
monthsafter
afterplanting.
planting.Significant
Significantdifferences
differences
quality,
werethen
thenobserved
observedininsoil
soilsolution
solutionnitrate
nitrateconcentrations
concentrationsand
andsoil
soilCO
CO
evolutionbetween
betweenthe
thepeanut
peanut
were
2 2evolution
UH–CTAHR
Benefits and Costs of Using Perennial Peanut as Living Mulch
treatmentsand
andthe
theblack
blackweed
weedmat
mattreatment
treatmentatatboth
bothlocations
locations(Figures
(Figures55&&6).
6).
treatments
SCM-27 — Aug. 2009
Table
5.Select
Selected
soil
properties
(pre-plant)
and
7 months
after
(post-plant)
perennial
peanut
establishment
Table5.5.
Select
soilproperties
properties
beforebefore
(pre-plant)
andseven
seven
months
after(post-plant)
(post-plant)
perennial
peanutestablishment
establishment
Table
soil
before
(pre-plant)
and
months
after
perennial
peanut
atat
thethe
at
the Poamoho
Research
An indicates
asterisk
indicates
that the between
difference
between
pre-plant
and
post-plant
Poamoho
Experiment
Station.Station.
Anasterisk
asterisk
indicatesthat
thatthe
thedifference
difference
betweenpre-plant
pre-plant
and
post-plant
values
Poamoho
Experiment
Station.
An
and
post-plant
values
is is values is
statistically
significant.
NS
indicates
no
significant
difference
between
the
two
values.
statisticallysignificant.
significant.NS
NSindicates
indicatesno
nosignificant
significantdifference
differencebetween
betweenthe
thetwo
twovalues.
values.
statistically
Treatment
Treatment
Mat
Mat
Seed-50
Seed-50
Seed-20
Seed-20
Stolon
Stolon
Sample
Sample
Time
Time
Pre-plant
-plant
Pre
Post-plant
-plant
Post
Significance
Significance
Pre-plant
-plant
Pre
Post-plant
-plant
Post
Significance
Significance
Pre-plant
-plant
Pre
Post-plant
-plant
Post
Significance
Significance
Pre-plant
-plant
Pre
Post-plant
-plant
Post
Significance
Significance
pH
pH
7.0
7.0
7.1
7.1
NS
NS
7.2
7.2
6.9
6.9
NS
NS
7.1
7.1
7.0
7.0
NS
NS
6.8
6.8
6.7
6.7
NS
NS
%%CC
1.3
1.3
1.5
1.5
NS
NS
1.5
1.5
1.4
1.4
NS
NS
1.4
1.4
1.4
1.4
NS
NS
1.4
1.4
1.3
1.3
NS
NS
<-----------------ppm-----------------------------------> >
<-----------------ppm
Ca
Mg
PP
KK
Ca
Mg
443
574
1739
315
443
574
1739
315
512
639
1998
374
512
639
1998
374
NS
NS
NS
**
NS
**
271
658
1949
322
271
658
1949
322
272
435
1771
292
272
435
1771
292
NS
NS
NS
NS
NS
NS
**
365
595
2000
295
365
595
2000
295
347
472
1881
285
347
472
1881
285
NS
NS
NS
NS
NS
NS
**
323
576
1675
299
323
576
1675
299
437
415
1592
286
437
415
1592
286
NS
NS
NS
NS
NS
NS
**
3
3
<-----------------g/dm
-------------<-----------------mm
g/dm
------------->>
Mn
Mn
FeFe
CuCu
ZnZn
161
161
55
99
99
105
105
33
77
66
* *
* *
* *
* *
156
156
55
1010
99
145
145
33
77
66
NS
NS
* *
* *
* *
163
163
55
99
99
128
128
33
77
66
NS
NS
* *
* *
* *
156
156
55
99
88
165
165
44
88
66
NS
NS
* *
* *
* *
Table
thethe
Table6.6. Select
Selectsoil
soilproperties
propertiesbefore
before(pre-plant)
(pre-plant)and
andseven
sevenmonths
monthsafter
after(post-plant)
(post-plant)perennial
perennialpeanut
peanutestablishment
establishmentatat
Table 6. Selected soil properties before (pre-plant) and 7 months after (post-plant) perennial peanut establishment
Waimanalo
WaimanaloExperiment
ExperimentStation.
Station.An
Anasterisk
asteriskindicates
indicatesthat
thatthe
thedifference
differencebetween
betweenpre-plant
pre-plantand
andpost-plant
post-plantvalues
valuesis is
at the Waimānalo Research Station. An asterisk indicates that the difference between pre-plant and post-plant values is
statistically
significant.
NS
indicates
no
significant
difference
between
the
two
values.
statistically
significant.
NS
indicates
no
significant
difference
between
the
two
values.
statistically significant. NS indicates no significant difference between the two values.
Treatment
Treatment
Mat
Mat
Seed
Seed-50
-50
Seed
Seed-20
-20
Stolon
Stolon
Sample
Sample
Time
Time
Pre
Pre-plant
-plant
Post
Post-plant
-plant
Significance
Significance
Pre
Pre-plant
-plant
Post
Post-plant
-plant
Significance
Significance
Pre
Pre-plant
-plant
Post
Post-plant
-plant
Significance
Significance
Pre
Pre-plant
-plant
Post
Post-plant
-plant
Significance
Significance
pH
pH
6.4
6.4
6.5
6.5
NS
NS
6.5
6.5
6.6
6.6
NS
NS
6.5
6.5
6.6
6.6
6.5
6.5
6.5
6.5
NS
NS
%%
CC
2.3
2.3
2.2
2.2
NS
NS
2.1
2.1
2.0
2.0
NS
NS
2.3
2.3
2.1
2.1
NS
NS
2.0
2.0
1.6
1.6
NS
NS
<-----------------<------------------ ppm-----ppm------------------------->
-->
PP
KK
Ca
Mg
Ca
Mg
277
938
3432
2166
277
938
3432
2166
456
817
4141
3131
2013
456
817
2013
**
**
NS
**
NS
341
3820
2429
341 1111
1111
3820
2429
488
657
4649
2127
488
657
4649
2127
**
**
NS
NS
297
3643
2263
297 1173
1173
3643
2263
275
956
4012
2195
275
956
4012
2195
**
**
NS
NS
NS
NS
307
1171
3883
2404
307
1171
3883
2404
335
728
4033
2299
335
728
4033
2299
**
**
NS
NS
NS
NS
Costs
Installation and maintenance costs on a per-acre basis are
summarized in Table 9. Labor is assumed to cost $12.50/
hour. The other cost assumptions are detailed below.
Installation
Plastic weed mat cost $1/linear ft, and 2420 linear ft/acre
were required, for a total materials cost of $2,400. Seeds
cost $15/pound, which means that the higher seeding rate
cost $810/acre and the lower one was $270. Stolons cost
$6/pound, with 14,500 stolons (116 lb) used for 1 acre
for a total cost of $696.
6
3 3
<---------mg/dm
>>
<---------mg/dm-----------------------------------Mn
FeFe
CuCu ZnZn
Mn
187
6565
99
66
187
7171
5252
44
33
**
* *
* *
* *
179
6868
99
77
179
5757
5252
44
33
**
* *
* *
* *
176
6666
88
66
176
5959
4747
44
33
**
* *
* *
* *
140
67
7
7
140
67
7
7
6363
3434
33
33
**
* *
* *
* *
Plastic weed mat installation required 24 hours/acre
for a total labor cost of $300. Drilling seed by hand
required 15 hours for the high seeding rate and 5 hours
for the low rate for costs of $272 and $91, respectively.
Walking speed was ~3 min/100 ft. Linear feet walked
was 29,185 and 9,728 per acre for high and low seeding
rates, respectively. Stolon preparation required 15 hours,
and planting required 25 hours, for a total of 40 hours at
a cost of $500.
Maintenance
At an irrigation frequency of three times per week for a
UH–CTAHR
Benefits and Costs of Using Perennial Peanut as Living Mulch
SCM-27 — Aug. 2009
Seed-53
Seed-18
Stolon
Mat
25
24
23
a
a
b bb
b
cb
22
21
Soil Temperature
(C)
20
Waimānalo
Waimanalo
Poamoho
Poamoho
Figure 7. Soil temperatures levels under mulch treatments
at Waimānalo and Poamoho 12 months after planting.
Values are means of 9 values. Means within locations with
different letters are significantly different at the 5% level.
34
Poamoho
32
a
a
N (%) in leaf tissue
Soil temperatue (°C)
26
Guava
Sapodilla
Figure 9. Guava and sapodilla tissue nutrient content
under mat and peanut treatments. Values are means
of three replications at two locations. Ten leaf pairs (3rd
expanded pair from branch tip) were composited from each
replication. Dotted lines represent the range of critical N
values established for guava (Uchida, 2000). Values with
different letters are significantly different at the 5% level.
a
30
28
b
Volumetric soil Moisture (%)
26
24
22
Waimanalo
a
8
3
d-5 eed-1 Stolon
S
See
55
Ma t
Waimanalo
a
50
a
ab
b
45
40
35
30
d
See
-53 ed-18 tolon
S
Se
Ma t
Figure 8. Volumetric soil moisture under mulch
treatments at Waimānalo and Poamoho 12 months
after planting. Values are means of 9 values. Means within
locations with different letters are significantly different at
the 5% level.
duration of 3 hours, each tree received 180 gallons/month,
or 34,500 gal/acre/month at a planting density of 192
trees/acre, with a water cost of $0.425/1000 gallons. This
results in an annual cost of $180. Supplemental irrigation
for peanut at the same duration and frequency as the tree
requires 228,096 gal/acre/month, or $1,344 per year.
A single spray event required 2 quarts/acre of Ranger
Pro® at a cost of $20 and 3 hours of labor at $37.50 for
a total cost of $57.50.
Plots were hand-weeded three times during the first 8
months of peanut establishment. This weeding required
an estimated 59, 89, and 77 hours/acre for the high seed
rate, low seed rate, and stolon treatments and resulted in
labor costs of $2212.50, $3337.50, and $2887.50, respectively.
Implications
The perennial peanut mulch treatments were competitive
with fruit trees in the short term, particularly for nitrogen.
Living mulch cost 55–87 percent more to establish than
weed mat, due primarily to the cost of water and the
labor for weed control. The most effective way to reduce
competition of peanut with trees during establishment
may be the limited use of organic or plastic mulch within
tree rows or around trees, although this will increase
7
8
Treatment
Mat
Treatment
Seed-54
Mat
Seed-18
Seed-54
Stolon
Seed-18
Stolon
Mat
Seed-54
Mat
Seed-18
Seed-54
Stolon
Seed-18
Stolon
<-------------- ----------------------------- %---------- ---------------- --------- >
N
P
K
Ca
Mg
Na
1.72
0.25
1.94
0.82
0.38
0.07
N
P
K
Ca
Mg
Na
1.25
0.32
2.04
0.97
0.36
0.09
1.72
0.25
1.94
0.82
0.38
0.07
1.12
0.28
2.08
0.91
0.34
0.09
1.25
0.32
2.04
0.97
0.36
0.09
1.3
0.27
2.27
0.83
0.32
0.73
1.12
0.28
2.08
0.91
0.34
0.09
1.3
0.27
2.27
0.83
0.32
0.73
1.6
0.19
2.09
0.93
0.23
0.01
1.09
0.22
1.90
1.00
0.23
0.03
1.6
0.19
2.09
0.93
0.23
0.01
1.24
0.19
1.84
0.98
0.23
0.03
1.09
0.22
1.90
1.00
0.23
0.03
1.34
0.20
1.80
1.01
0.24
0.02
1.24
0.19
1.84
0.98
0.23
0.03
1.34
0.20
1.80
1.01
0.24
0.02
***
NS
NS
NS
NS
NS
NS
***
NS
**
***
***
***
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
***
NS
**
***
***
NS
NS
NS
NS
NS
NS
<-------------- -------- ---------ppm -------- --------->
Fe
Mn
Zn
Cu
54
48
9
10
Fe
Mn
Zn
Cu
44
36
15
9
54
48
9
10
48
39
20
9
44
36
15
9
46
35
8
9
48
39
20
9
46
35
8
9
53
210
14
8
47
136
17
8
53
210
14
8
54
171
15
8
47
136
17
8
51
184
15
9
54
171
15
8
51
184
15
9
NS
NS
*
***
NS
***
NS
***
NS
NS
*
***
NS
NS
NS
NS
NS
***
NS
***
NS
NS
NS
NS
Waimanalo
Treatment
N
P
K
Ca
Mg
Na
<--- -------------------------------- %---------------------------------- > 0.9
Mat
1.17
0.11
1.09
1.38
0.32
Treatment
N1.09
P0.16
K1.11
Ca1.5
Mg0.4
Na
Seed-54
0.09
Waimanalo
Mat
1.17
0.11
1.09
1.38
0.32
0.9
Seed-18
1.05
0.11
1.05
1.55
0.4
0.09
Seed-54
1.09
0.16
1.11
1.5
0.4
0.09
Stolon
1.16
0.13
1.19
1.24
0.35
0.1
Seed-18
1.05
0.11
1.05
1.55
0.4
0.09
Stolon
1.16
0.13
1.19
1.24
0.35
0.1
Poamoho
Mat
1.26
0.11
1.23
1.20
0.4
0.15
Seed-54
0.90
0.13
1.03
1.09
0.41
0.21
Poamoho
Mat
1.26
0.11
1.23
1.20
0.4
0.15
Seed-18
0.98
0.10
0.93
1.56
0.56
0.16
Seed-54
0.90
0.13
1.03
1.09
0.41
0.21
Stolon
1.04
0.15
1.03
1.34
0.45
0.15
Seed-18
0.98
0.10
0.93
1.56
0.56
0.16
ANOVA
1.04
0.15
1.03
1.34
0.45
0.15
Treatment Stolon
ANOVA
(T)
***
NS
NS
NS
NS
NS
Treatment
Location (L)
NS
NS
NS
NS
*
***
***NS
NSNS
NSNS
NSNS
NSNS
NSNS
T(T)
xL
Location (L)
NS
NS
NS
NS
*
***
Tx L
NS
NS
NS
NS
NS
NS
24
4727
2435
27
35
NS
*
NSNS
*
NS
6
8 7
6 9
7
9
*
NS
* NS
NS
NS
5
5 4
5 5
4
5
NS
NS
NSNS
NS
NS
25
2832
2535
32
35
NS
NS
NSNS
NS
NS
B
29
B
32
29
32
32
29
32
29
27
32
27
28
32
30
28
30
NS
NS
NS
NS
NS
NS
Benefits and Costs of Using Perennial Peanut as Living Mulch
53
8366
5385
66
85
NS
NS
NSNS
NS
NS
Fe
Mn
Zn
Cu
B
<-------------------------->
52
65 ppm -----------------7
5 --------------25
Fe49
Mn42
Zn 7
Cu5
B36
52
6544
7 8
5 5
2536
89.00
4950
4259
7 10
5 6
3627
89.00
44
8
5
36
5083
5947
10 8
6 5
2728
Table 8. Tissue nutrient levels of Chico 8 months after planting. An asterisk indicates statistical significance. NS indicates no
<--- ------------<--------------------------- ppm ------------------ -------------- >
statistically significant difference
was----------------detected. ---- %-------------------------- --------- >
Table
8. Tissue
nutrient
levels
of Chico8 8months
months
after
planting.
asterisk
indicates
statistical
significance.
NS no
indicates
no
Table
8. Tissue
nutrient
levels
of sapodilla
after
planting.
An An
asterisk
indicates
statistical
significance.
NS indicates
statistically
statistically
significant
difference was detected.
significant
difference
was detected.
ANOVA
Treatment (T)
ANOVA
Locatio n (L)
Treatment (T)
Tx L
Locatio n (L)
Tx L
Poamoho
Poamoho
Waimanalo
Waimanalo
was detected.
Table 7. Tissue
nutrient
levels of guava
8 months after planting. An asterisk indicates statistical significance. NS indicates no statistically significant difference
statistically
significant
difference
was
detected.
<------------------------------------------ %---------- ---------------- --------- > <-------------- -------- ---------ppm -------- --------->
Table 7. Tissue nutrient levels of Guava 8 months after planting. An asterisk indicates statistical significance. NS indicates no
statistically
significant
difference
was detected.
Table
7. Tissue
nutrient levels
of Guava
8 months after planting. An asterisk indicates statistical significance. NS indicates no
UH–CTAHR
SCM-27 — Aug. 2009
UH–CTAHR
Benefits and Costs of Using Perennial Peanut as Living Mulch
SCM-27 — Aug. 2009
Table 9. Estimated cost per acre of mulch establishment (12 months) in the Waimānalo and Poamoho Research
Station trials.
Weed mat Seeded at
Seeded at
Cuttings
54 lb/acre
18 lb/acre
(stolons)
Installation
Materials
Labor
Irrigation
$2,400
$300
$810
$272
$180
$1,344
$270
$91
$696
$500
Weed control
Chemicals
Labor
$2,213
$3,337
$2,888
Total
$4,697
$5,100
$5,486
$2,880
--------------------------$58--------------------------
costs associated with peanut establishment. For example,
Typar® weed barrier circles would cost $3.50 per tree for
292 trees per acre and increase costs by $1,022 per acre.
However, the higher respiration rate under living mulch
demonstrated the potential of peanut to enhance soil
microbial activity compared to weed mat alone.
The 54-lb/acre seeding rate was the most cost-effective
option of the three mulch treatments. The stolons cost
nearly as much as the seed for the 54-lb/acre treatment,
while the labor costs were almost double. When the
high installation costs are added to the extra cost of
weed control for establishment from cuttings, it cost 7.5
percent more than the 54-lb/acre treatment. The higher
installation cost of the 54-lb/acre rate compared with the
18-lb/per acre rate were offset by the higher labor cost
associated with weeding in the lower seeding rate. Inoculation with rhizobia, not used in this trial, would cost
very little and might improve establishment, particularly
in poor soils.
The cost of establishing seeded perennial peanut living mulch may be reduced by (1) planting at the beginning of the wet season to reduce or eliminate the need
for supplemental irrigation, (2) replacing hand weeding
with chemical control, and (3) utilizing mechanization
(i.e., tractor and appropriate implements) for drilling or
broadcasting and incorporating. For growers interested
in organic certification, establishment of living mulch
using herbicides must be done three or more years
before applying. If herbicide use is not an option, then
the peanut should be planted as densely as possible, the
seeds should be inoculated before planting, and regular
mowing should be done as soon as the canopy closes.
The use of living mulch has the potential to improve
the sustainability of tropical fruit agro-ecosystems in the
long run, although cost issues and short-run competition
can reduce the expected benefits. The relative cost of the
weed mat treatment may increase more than the peanut
treatments in the long run as shipping costs increase.
While some of the benefits associated with increased
sustainability may not result in an increased return to
producers, consumers may be expected to pay more for
items produced if they are labeled as using sustainable
methods, and this increased return should also be examined before a grower makes a final decision.
Acknowledgments
Salaries and research support were provided in part by
the Hawaii Farm Bureau Federation, the Hawai‘i Department of Agriculture, and the USDA TSTAR program.
We thank Roger Corrales, Susan Migita, and the staff of
CTAHR’s Waimānalo and Poamoho Research Stations
for technical assistance with this project. We also thank
the Hawaii Cooperative of Organic Farmers, Frankie’s
Nursery, Poamoho Produce, and Drs. Joe DeFrank and
Ali Fares (CTAHR) for technical advice. We gratefully
acknowledge the contributions of Rebecca Mitschele,
Gabriel Ortega, Jensen Uyeda, Natalie Pullano, Christina
Theocharis, and Brooke Moreno.
9
UH–CTAHR
Benefits and Costs of Using Perennial Peanut as Living Mulch
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Mention of a product name does not imply endorsement of the product or its recommendation to the exclusion of
other suitable and appropriate products.
10