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Sistema de Información Científica
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
UTILIZATION OF BY-PRODUCTS FROM THE TEQUILA INDUSTRY. PART 6: FERTILIZATION
OF POTTED GERANIUM WITH A SLAUGHTERHOUSE WASTE COMPOST
Gilberto ÍÑIGUEZ
1
and David M. CROHN
2
1
Universidad de Guadalajara. Departamento de Madera, Celulosa y Papel. Km. 15.5 Carretera Guadalajara-Nogales.
Las Agujas, Mpio. de Zapopan, Jalisco. Apartado Postal 52-93. C.P. 45020, Guadalajara, Jalisco, México
2
University of California. Riverside, California 92521,USA
(Recibido junio 2003, aceptado julio 2004)
Keywords: animal solid waste compost, slaughterhouse waste compost, geranium, fertilizer, potting media
ABSTRACT
A greenhouse pot study was conducted to evaluate the use of a slaughterhouse waste compost
(SWC) as fertilizer for potted geranium plants. This SWC was mixed with agave bagasse compost
(ABC) at rates of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% by volume. The
effects of the SWC on the germination and initial growth of
Raphanus sativus
were also exam-
ined. Samples of SWC and ABC were used to prepare 6 different mixtures: (1), 50% sand, 25% bark
and 25% peat, (2), 50% sand and 50% peat, (3), 50% sand, 25% bark and 25% SWC, (4), 50% sand
and 50% SWC (5), 50% sand, 25% bark and 25% ABC and (6), 50% sand and 50% ABC. Samples
of these mixtures and SWC and ABC, were analyzed for bulk density, easily available water
(EAW) and water buffering capacity (WBC). Potted geranium plants grew well in mixtures of
SWC and ABC with no additional fertilization. High volumes of SWC (70 to 100%) had no adverse
effect on root growth, on subsequent plant growth and development, or on the flowering pro-
cess. SWC had no detrimental effect on
Raphanus sativus
seeds germination (
p
0.05). Condi-
tioning soils with SWC and ABC increased soil bulk density (
p
0.05). Easily available water and
water buffering capacity results suggest that SWC and ABC can substitute peat.
Palabras clave: composta de desechos animales, desechos de rastros, geranio, fertilizante, substrato para macetas
RESUMEN
En el presente trabajo se realizó un estudio de invernadero para evaluar como fertilizante la
utilidad de una composta a base de desechos de rastros (CDR) para el crecimiento de plantas de
geranio. Esta composta se mezcló a su vez con otra a base sólo de bagazo de agave (CBA) en
proporciones en volumen del 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% y 100%.
También se evaluó el efecto de la CDR en la germinación y desarrollo inicial de
Raphanus sativus
.
Por otro lado se utilizaron muestras de CDR y CBA para preparar 6 diferentes mezclas: (1), 50% de
arena, 25% de corteza y 25% de turba, (2), 50% arena y 50% de turba, (3), 50% de arena, 25% de
corteza y 25% de CDR, (4), 50% de arena y 50% de CDR (5), 50% de arena, 25% de corteza y 25%
de CBA y (6), 50% de arena y 50% de CBA a las que se les determinó densidad, agua fácilmente
asimilable y capacidad compensadora de agua. Los geranios se desarrollaron muy bien en las
macetas sin la necesidad de una fertilización adicional. Proporciones altas de CDR (70 al 100%) en
las macetas, no tuvieron efectos dañinos en la raíz, desarrollo y floración. No se presentaron
efectos negativos al germinar semillas en CDR (
p
0.05). El acondicionamiento de suelos con
CDR y CBA aumentó la densidad de los mismos (
p
0.05). Los resultados en términos de agua
fácilmente disponible y capacidad compensadora de agua, sugieren que las compostas a base de
desechos de rastros y de bagazo de agave pueden ser un sustituto de la turba.
Rev. Int. Contam. Ambient. 20 (2) 53-58, 2004
G. Íñiguez and D.M. Crohn
54
INTRODUCTION
Pork is an important part of Mexican diet. Although waste
by-products from the butchering of hogs are relatively
small, the disposal of large intestines poses a challenge
for Mexican swine slaughterhouses. Most unmarketable
animal parts may be rendered without special handling.
Intestinal material, however, must be cleaned to remove
fecal matter before it can be rendered. Because clean-
ing requires special handling, the purchase of water, and
leaves a polluted effluent, Mexican slaughterhouses land-
fill the large intestines that result from their operations.
The Mexican tequila industry also generates signifi-
cant amounts of solid waste materials. To manufacture
tequila, fermentable sugars are removed from the agave
plant leaving a bagasse that must be disposed of. To dis-
pose of the agave bagasse, distilleries typically burn the
material as it is produced or they allow it to accumulate
in piles that are eventually either intentionally or inad-
vertently burned. Air pollutants generated from the burn-
ing of agave bagasse are not controlled.
A beneficial alternative is needed to current disposal
practices for both of these waste products. This paper
considers the use of a slaughterhouse waste compost
(SWC) product derived from swine large intestines and
agave bagasse. When agave bagasse is composted to-
gether with swine slaughterhouse waste, the intestinal
material serves as a source of labile carbon and nitrogen
while the bagasse works as an effective bulking agent.
Composting serves as means of stabilizing the materials
and inactivating pathogens associated with the swine
wastes (Íñiguez and Vaca 2001). Composts can assist in
agricultural crop production by improving soil physical
properties, such as by lowering bulk density and increas-
ing water holding capacity. To a limited extent compost
may also assist crops by supplying essential nutrients
(McConnell
et al.
1993; Rosen
et al
. 1993; Raviv 1998).
Compost quality is generally a function of particle size,
pH, soluble salts, maturity and the absence of such un-
desirable components as weed seeds, heavy metals and
phytotoxic compounds. The purpose of this investigation
was to test for a possible SWC phytotoxicity and to evalu-
ate the potential for SWC as a growth medium for pot-
ted geraniums as an example of the potential horticul-
tural use of the material.
MATERIALS AND METHODS
This study considered a slaughterhouse waste com-
post (SWC) produced by mixing swine abattoir wastes
(principally large intestines) with an agave bagasse bulk-
ing agent in a 2:3 wet mass ratio and then aerobically
composted in turned windrows (Iñiguez and Vaca, 2001).
Agave bagasse was also composted with 5% (dry basis)
urea. The resulting agave bagasse compost (ABC) was
mixed with the SWC during the growth experiments.
The SWC and ABC were analyzed for significant
physical and chemical properties. Germination and seed-
ling growth tests were used to test the SWC for poten-
tial phytotoxicity and the influence of different SWC ra-
tios on plant production was evaluated. Finally, SWC and
ABC were considered as possible replacements for
materials such as peat and bark, which are commonly
used to formulate potting soil mixtures.
Compost hydrologic and physiochemical character-
istics
Samples of the SWC and ABC were analyzed for
bulk density, saturation water content, easily available
water (EAW) and water buffering capacity (WBC).
EAW (g cm
-3
) is a measure of the water released by the
sample when the suction of a water column increases
from 0 to –50 cm. It represents that portion of soil water
that can be easily absorbed by the roots. The WBC (g
cm
-3
) is the volume of water released by the samples
when suction increases from a water column measure-
ment of –50 to –100 cm.
Samples were compacted in brass cylinders 5.4 cm
in diameter and 6 cm high using a mechanical compac-
tor to produce consistent soil cores (Richards
et al
. 1965)
and saturated with water overnight. Saturation water
content was determined by registering the differences in
mass. Sample bulk densities (g cm
-3
) were calculated by
considering the brass cylinder volumes and the sample
dry masses. To measure water retention capacity, satu-
rated samples were subjected to a metric potential of –
50 cm with a 5 bar ceramic plate extractor for 24 h.
Afterwards, samples were weighed and placed again on
the ceramic plate extractor at a metric potential of –100
cm for 24 h. Water retention capacity measurements
were determined by mass differences. Percent of mois-
ture was determined by drying a known amount of me-
dium at 105
o
C for 24 h.
Germination and seedling growth tests
To test germination, 25 cm
3
of the SWC were placed
4-5 mm deep in 10 cm petri dishes and moistened to
saturation with deionized water. A control was prepared
with a medium speed filter paper set in a petri dish with
3 ml of deionized water. The experiment (one-way clas-
sification analysis of variance) included ten replications
of all treatments. radish (
Raphanus sativus)
seeds were
placed in each petri dish in the compost or filter paper
and allowed to germinate at 22
±
1
o
C. Petri dishes were
kept covered with their lids until radish emerged. Each
dish was watered as required. Germination percentages
were calculated 7 days after germination started.
For the SWC seedling growth test, radish seeds were
placed in petri dishes and kept moist with filter paper.
SLAUGHTERHOUSE WASTE COMPOST
55
After their emergence (within 3 days), seedlings were
planted in two polystyrene seedling flats (34 x 34 cm)
with 100 cells (2.5 x 2.5 x 7 cm) each, one for growth
with peat moss (as control) and one for growth with
SWC. Plants grew with light conditions of 12 h per day.
Seedling and root lengths were measured 10 days after
planting.
Plant production experiments
The SWC was sieved with a 1-
cm mesh and then
mixed with ABC previously grounded to pass through a
7.5-mm mesh (
Table I
) to represent 0%, 10%, 20%,
30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% of the
total mixture volume. Hybrid geranium HF2 red plants
germinated for twelve days in trays and were then trans-
ferred to pots. A completely randomized experiment was
used with four replicates in a glass greenhouse using
plastic pots 15 cm in diameter and 19 cm deep filled with
1.5 L of each mixture. Plants were watered daily with
demineralized water to “container capacity” while avoid-
ing leaching. During the experiment no additional fertili-
zation was performed. Plants were harvested 120 days
after planting. Leaves, stems, roots and flowers were
dried at 65
o
C
for 48 h and weighed. Leaves and flowers
were counted and stems lengths measured.
Potting mixture physical properties
Six different mixtures were prepared by volume and
examined (see
Table
IV)
: Mix 1 (50% sand, 25% bark,
and 25% peat), Mix 2 (50% sand and 50% peat), Mix 3
(50% sand, 25% bark and 25% SWC), Mix 4 (50% sand
and 50% SWC), Mix 5 (50% sand, 25% bark and 25%
ABC), and Mix 6 (50% sand and 50% ABC). These
mixtures were analyzed for bulk density, EAW, and WBC
with the same procedures used to evaluate the composts
alone.
Analytical methods
Mixture electrical conductivity and pH values were
measured in a saturated pasted extract and in a satu-
rated paste using a pH meter and a conductivity meter,
respectively. Ash was measured after ignition at 550 °C
for 2 h in a muffle furnace. Total nitrogen and total car-
bon were determined by analysis in a Carlo Erba
®
NA
1500 Carbon-Nitrogen elemental analyzer. Analysis of
extractable nitrate-N, and ammonium-N were based on
an extraction with a solution of 2% acetic acid and de-
termined according to the diffusion-conductivity method
as described by Carlson
et al
. (1990). Total P, S, K, Ca,
Mg, Na, Zn, Mn, Fe, Cu and Mo were measured using a
nitric acid/hydrogen peroxide microwave digestion analy-
sis by atomic absorption spectroscopy or inductively
coupled plasma atomic emission spectrometry. All ana-
lytical methods were obtained from ALSOPM (2001) and
results were subjected to one-way ANOVA analysis, fol-
lowed by the LSD test at p
<
0.05 (Montgomery 1991).
RESULTS AND DISCUSSION
Compost hydrologic and physiochemical character-
istics
SWC and ABC pH values were 7.0 and 7.2, respec-
tively (
Table I
), which are within the preferred range
for most agricultural crops (Rynk 1992). Fitzpatrick
et
al
. (1988) reported that values of commercially produced
composts typically range from 6.7 to 7.7. C/N ratios for
the SWC and ABC composts were 8.1 and 17.0, re-
spectively. Composts with C/N ratios less than 20 are
often considered best for plant production (Davidson
et
al
. 1994). Composts with C/N ratios higher than 30 may
result in nutrient immobilization (Zucconi
et al
. 1981).
The SWC had greater fertility values than the ABC in
terms of NH
4
+
-N, P, S, Mg, Zn, Mn, Fe, Cu and Mo (
p
>
0.05) and the addition of SWC to soil would raise its
overall nutrient content, particularly in regard to P. The
relatively elevated nitrate-N and total N concentration
in the ABC is possibly due to the fertilizer added during
its composting and does not, therefore, represent a re-
claimed nutrient. The ABC had a lower ash content than
SWC (
p
> 0.05), however SWC and ABC had conduc-
tivity values of 9.98 and 6.49 mmhos cm
-1
, respectively,
values statistically different (
p
> 0.05).
SWC
ABC
pH
7.00
7.20
Dry matter (%)
88.80
67.30
Ash (%)
a
62.20
31.90
Conductivity (mmhos cm
-1
)
9.98
6.49
Extractable NH
4
+
- N (mg kg
-1
)
a
473.00
15.00
Extractable NO
3
- N (mg kg
-1
)
a
1892.00
2481.00
Total N (%)
a
3.10
3.70
Total C (%)
a
25.30
63.00
C/N ratio
8.10
17.00
Total P (%)
a
1.24
0.113
Total K (%)
a
0.29
0.564
Total S (mg kg
-1
)
a
4797.00
1545.00
Total Ca (%)
a
4.15
6.55
Total Mg (%)
a
0.495
0.386
Total Na (mg kg
-1
)
a
1846.00
995.00
Total Zn (mg kg
-1
)
a
459.00
67.00
Total Mn (mg kg
-1
)
a
300.00
34.00
Total Fe (mg kg
-1
)
a
6766.00
543.00
Total Cu (mg kg
-1
)
a
214.00
14.00
Total Mo (mg kg
-1
)
a
1.60
0.60
TABLE I.
CHARACTERISTICS OF SLAUGHTERHOUSE
WASTE (SWC) AND AGAVE BAGASSE COMPOSTS
(ABC)
a
Dry basis
G. Íñiguez and D.M. Crohn
56
Germination test and seedling growth
Table II
shows the effect of SWC on germination
and on the stem and root length development of
Rhaphanus sativus
10 days after planting. There was
no statistical difference (
p
<
0.05) between the number
of seeds germinated in deionized water (control) and the
number germinated in SWC. Stem lengths and stem/root
ratios of
Rhaphanus sativus
were 11.7 and 12.3% higher
for seedlings grown on peat moss (control) than for seed-
lings grown on SWC, suggesting the possibility of limited
phytotoxicity. However, root lengths were similar for
seedlings grown on either peat moss or SWC.
Plant production
The plant production experiments were structured to
examine SWC phytotoxicity compared to ABC. Phytoto-
xicity was believed to depend on the amount of SWC em-
ployed. Experimental results suggest, however, that the rich
nutrient environment provided by the SWC compensates
any potential phytotoxic compounds given by the ABC.
Plant tissue production (
Table III
) increased mark-
edly when SWC
40% and were depressed when ABC
40%. Flower and leaves production was greatest when
SWC
70%. By contrast, flower production was effec-
tively curtailed when ABC
40% and overall tissue pro-
duction was severely depressed when ABC
80%. Shoot
dry weights (stems, leaves and flowers) were statisti-
cally significantly greater for SWC mixes than for either
ABC alone or 10% SWC (p
>
0.05). The amount of leaves
was approximately half (an average of 9.2 with 100%
ABC and 10.2 with 90% ABC) than that obtained when
S in comparison to the other ABC-SWC containing pots.
Media with high SWC volumes (70 to 100%) had no
apparent adverse effect on root growth, subsequent plant
growth and development, as well as on the flowering pro-
cess. Root dry weights ranged from 0.697 g to 1.016 per
plant as the SWC percentage rose from 30 to 100% of
the growth media. The shoot/root ratio was not affected
by the SWC increase in the growth media; it was consis-
tently between 6.01 and 8.30 in the 10 to 100% SWC
containing crops. Plant stem lengths were between 18.5
and 24.12 cm for the 40 to 100% SWC added plants. The
highest yield of leaves was for the media containing 70
and 100% SWC. Pots with 70, 90 and 100% SWC had an
average of 56.2, 41.5 and 40.2 flowers per plant, which
correspond to 675, 745, and 688 g of flowers dry weight.
SWC appeared to be a superior potting mixture com-
pared to ABC. ABC is deficient in many nutrients that
Treatment
Control
SWC
Germination (%)
95
a
87
a
Component
1
Stem length (cm)
3.38
a
2.75
b
Root length (cm)
5.73
a
5.53
a
Stem/root length ratio
0.65
a
0.57
b
TABLE II.
EFFECT OF SWC ON GERMINATION AND ON
THE STEM AND ROOT LENGTH OF
RAPHANUS
SATIVUS
10 DAYS AFTER PLANTING
1
Each value represents the mean value of ten replicates. Each replicate
represents the mean value of 10 seedlings
a, b
Values followed by the same letter in a given row do not differ
at
p
0.05
Shoot
1
Root
Stem
Flowers
SWC:ABC
Dry wt
dry wt
Shoot
2
:root
length
No. of leaves
No. of flowers
dry wt
(%)
(g)
(g)
ratio
(cm)
per plant
per plant
(g)
0:100
0.319
a
0.281
a
3.65
a
0.50
a
9.2
a
0
a
0
a
10:90
1.164
a
0.190
a
6.01
b
4.12
ab
10.2
a
0
a
0
a
20:80
3.347
b
0.503
ab
6.59
bc
11.12
bc
18.0
b
0
a
0
a
30:70
4.443
bc
0.697
bc
6.40
bc
13.62
cd
20.0
bcd
0
a
0
a
40:60
6.114
cde
1.016
c
6.13
b
18.50
cde
20.7
bcde
0
a
0
a
50:50
5.100
bcd
0.844
bc
6.17
b
18.62
de
21.0
bcde
6.7
ab
0.095
a
60:40
5.523
cd
0.862
bc
6.86
bc
19.75
de
18.2
bc
0
a
0
a
70:30
6.136
cde
0.945
c
6.98
bc
21.90
e
28.2
f
56.2
d
0.675
b
80:20
6.171
cde
0.967
c
6.57
bc
20.50
de
22.5
cde
28.5
bc
0.413
b
90:10
7.437
e
0.980
c
8.30
c
24.12
e
22.7
de
41.5
cd
0.745
b
100:0
6.860
de
0.971
c
7.35
bc
19.90
de
24.5
ef
40.2
cd
0.688
b
LSD
1.859
0.384
1.560
7.436
4.253
24.629
0.418
TABLE III.
EFFECT OF THE SWC ADDITION ON THE SHOOT DRY WT, ROOT DRY WT,
SHOOT:ROOT RATIO, STEM LENGTH, NUMBER OF LEAVES, NUMBER OF
FLOWER AND FLOWERS DRY WEIGHT PER PLANT
1
Stems with leaves and flowers
2
Stems and leaves
a, b, c, d, e, f
Values followed by the same letter in a given column do not differ at
p
0.05 by LSD test
SLAUGHTERHOUSE WASTE COMPOST
57
are contained in SWC, including Zn (34 vs. 300 mg kg
-1
),
Cu (14 vs. 214 mg kg
-1
), Mo (0.6 vs. 1.6 mg kg
-1
), and S
(1545 vs. 4797 mg kg
-1
), and most particularly P (0.113%
vs. 1.24%). Several factors may therefore be contribut-
ing to the differences observed in the germination ex-
periments. It is likely that the available phosphorus in the
SWC was high relative to the ABC and that much of the
difference in performance between the two materials
may be explained by the difference in availability of this
important macronutrient.
Potting mixture physical properties
Both SWC and ABC (
Table IV
) showed similar
physical properties to peat when mixed with sand and
bark in the potting soil mixtures. SWC contains signifi-
cant ash (0.51 g/cm
3
) and is heavier than ABC (0.35 g
cm
-3
). Bulk densities of SWC mixtures were therefore
slightly greater than those with ABC or peat. The EAW
and WBC of ABC (1.34 g/g and 1.26 g/g, respectively)
were significantly greater than those of SWC (0.93 g/g
and 0.90 g/g), but this differences were not apparent in
the mixtures. Mixtures without bark did not show dif-
ferences in either EAW or WBC. With bark, SWC mix-
ture EAW values were an average of 25% greater than
the ABC or peat mixtures. WBC values were 21%
greater, although the difference in WBC between the
peat and SWC mixtures with bark were not statisti-
cally significant.
CONCLUSIONS
According to these results, it seems that geranium
plants could be grown satisfactorily with no florescence
problems in SWC but that ABC alone would not be a
good growth medium. When SWC is mixed with ABC,
Mixtures
1
Measurement
1
2
2
3
3
4
4
5
5
6
6
7
SWC
8
ABC
9
Bulk density (g/cm
3
)
0.93
ab
0.95
bc
0.97
cd
0.98
d
0.92
a
0.91
a
0.51
e
0.35
f
Easily available water (EAW)
(g water/g sample)
0.20
a
0.32
b
0.25
c
0.33
b
0.20
a
0.33
b
0.93
d
1.34
e
Water buffering capacity (WBC)
(g water/g sample)
0.19
ab
0.26
cd
0.23
bc
0.31
d
0.19
a
0.28
d
0.90
e
1.26
f
TABLE IV.
PHYSICAL PROPERTIES OF LABORATORY PREPARED MIXTURES
1
Percentages by volume
2
50% sand, 25% bark and 25% peat. Standard University of California mix used as reference
3
50% sand and 50% peat. Standard University of California mix used as reference
4
50% sand, 25% bark and 25% SWC
5
50% sand and 50% SWC
6
50% sand, 25% bark and 25% ABC
7
50% sand and 50% ABC
8
Slaughterhouse waste compost
9
Agave bagasse compost
Values followed by the same letter in the same row do not differ at
p
0.05 by LSD test
70-100% SWC is required to produce acceptable plants.
In terms of physical properties, both ABC and SWC could
substitute for peat in potting soil mixtures. However, SWC
provides a more fertile growth environment than ABC.
ACKNOWLEDGEMENTS
This cooperative research was supported by the
Consejo Estatal de Ciencia y Tecnología de Jalisco
(COECyT). The authors are indebted to Ms. Sc. Arturo
Camacho for expert statistical assistance and to Donald
Merhaut for his consideration of the nutrient value of
the materials
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