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Changes in the physical properties of two Acacia compost-based growing media and their effects on carob (Ceratonia siliqua L.) seedling development


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In arid zones, the use of compost for plant production in forest nurseries is hindered by a lack of water. The main objectives of this study were (1) to evaluate the physical stability of composts produced from shredded branches of Acacia cyanophylla and A. cyclops subjected to a repeated drying and wetting cycles, similar to those used at the operational scale in nurseries in arid regions and to compare these composts with a standard peat-vermiculite (PV) substrate; (2) to identify the relevant substrate physical variables that correlate with seedling growth. Carob (Ceratonia siliqua L.) was cultivated during a production cycle of 27 weeks in a completely randomized block experiment. Substrate physical variables were measured at the beginning, middle and end of the experiment. Seedling growth variables were evaluated over the course of the production cycle, while gas exchange and water-relation variables were measured during a wetting and drying cycle at the end of the experiment. All three substrates produced vigorous seedlings with well-developed root systems that colonized the entire root plug. The growth of seedlings produced in the PV substrate was better than those grown in the compost-based substrates. No significant differences in gas exchange capacities and water relation variables were observed among the three substrates at the end of experiment with the exception of net photosynthesis, which was higher for the PV substrate at high substrate matric potential. Excessive drainage was negatively correlated with growth variables while water availability in the early growth phase and air porosity towards the end of experiment were positively correlated. Performance of the two composts could be increased by improving their initial structure and stability and by adjusting the irrigation regime.
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New Forests
International Journal on the Biology,
Biotechnology, and Management of
Afforestation and Reforestation
ISSN 0169-4286
Volume 43
Number 3
New Forests (2012) 43:267-286
DOI 10.1007/s11056-011-9280-x
Are composts from shredded leafy branches
of fast-growing forest species suitable as
nursery growing media in arid regions?
Mustapha Bakry, Mohammed
S.Lamhamedi, Jean Caron, Hank
Margolis, Abdenbi Zine El Abidine,
M’Hammed Bellaka & Debra C.Stowe
1 23
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Are composts from shredded leafy branches
of fast-growing forest species suitable as nursery growing
media in arid regions?
Mustapha Bakry Mohammed S. Lamhamedi Jean Caron
Hank Margolis Abdenbi Zine El Abidine M’Hammed Bellaka
Debra C. Stowe
Received: 30 November 2010 / Accepted: 5 August 2011 / Published online: 21 August 2011
ÓSpringer Science+Business Media B.V. 2011
Abstract The morpho-physiological quality of seedlings is negatively affected by the
wide scale use of forest soils as substrates in developing countries. With the objective of
finding long-term sustainable supply of growing media, compost was produced from
shredded branches of three fast growing species (Acacia cyanophylla (AA), Acacia cyclops
(AS) and Eucalyptus gomphocephala (EG). The composting process covered three different
periods over the course of a year. Pile temperatures were monitored daily and the composts
were routinely sampled and analyzed for 19 chemical variables. Although composting is
feasible year-round in arid climates, compost produced in the humid cool conditions of
autumn, winter and early spring reaches the maturation phase more quickly than compost
produced under hot, dry summer conditions. It also requires less turning and water. The
evolution of the composting process and quality of the final product can be assessed using
three chemical variables (C/N, pH, EC). Seed germination rates in the three types of
compost were similar to that in a peat:vermiculite substrate and vigorous high quality
seedlings were produced in the two acacia composts. However, compost-grown seedlings
M. Bakry (&)H. Margolis D. C. Stowe
´partement des Sciences du bois et de la fore
ˆt, Faculte
´de Foresterie,
de Ge
´ographie et de Ge
´omatique, Pavillon Abitibi-Price, Universite
´Laval, 2405 rue de la Terrasse,
´bec, QC G1V 0A6, Canada
M. S. Lamhamedi
Direction de la Recherche Forestie
`re, Ministe
`re des Ressources Naturelles et de la Faune du Que
2700 rue Einstein, Que
´bec, QC G1P 3W8, Canada
J. Caron
´partement des sols et de ge
´nie agro-alimentaire, Faculte
´des Sciences de l’Agriculture et de
l’Alimentation, Pavillon Comtois, Universite
´Laval, 2425 rue de l’Agriculture, Que
QC G1V 0A6, Canada
A. Zine El Abidine
´cole Nationale Forestie
`re d’inge
´nieurs BP 511, Tabriquet, Sale
´, Morocco
M. Bellaka
Centre Re
´gional de la Recherche Forestie
`re de Marrakech, Circuit de la Palmeraie,
Km 2.5, B.P 13360, Poste Annakhil, Ain Itti, Marrakech, Morocco
New Forests (2012) 43:267–286
DOI 10.1007/s11056-011-9280-x
Author's personal copy
had significantly smaller shoots and root systems than those produced in peat substrate.
Principal components analyses showed that the quality of a compost-based substrate is
reproducible and that its final chemical composition can be predicted from its raw organic
materials. The EG composts had higher pH than the acacia composts, whereas the AA and
EG composts were higher in mineral salts than the AS.
Keywords Nursery substrates Compost Forest biomass Arid zones
Among the key factors which have a significant effect on the germination, growth and
physiology of nursery-grown tree seedlings are the composition and physicochemical
properties of the substrate in which the plants are grown (Lazcano et al. 2010; Bernier and
Gonzalez 1995). These factors can be optimised to significantly improve seedling growth,
root plug cohesion, substrate water holding capacity, gas diffusion and nutrient uptake,
while reducing leaching of the substrate solution.
In several developing countries, substrates are generally composed of mineral soils,
forest humus, sand and manure (Miller and Jones 1995). The physico-chemical properties
vary from year to year and among nurseries, depending on the source of the components
and their availability. In addition to being a potential source of weeds and diseases
(Lamhamedi et al. 2000), this practice does not facilitate the standardization and continual
improvement of cultural techniques for seedling production in forest nurseries. The use of
such substrates in North Africa hinders the improvement of seedling growth and survival
rates in reforestation programs. This necessitates repeated fill planting because the planted
seedlings lack the morpho-physiological qualities for successful establishment under
conditions of severe temperature and water stresses. The increase in the price of peat
(Ribeiro et al. 2007), as well as its environmental importance in maintaining biodiversity
(Fenner et al. 2007; Warner and Asada 2006), have increased the social pressure against
peat exploitation for substrate use. This has forced nursery managers to search for peat
substitutes that are socially, economically and ecologically acceptable.
In an effort to find long term alternatives to peat substrates, several recent studies have
focused on aerobic composting of various locally-available organic materials (Abad et al.
2001). The most frequently used materials are solid municipal waste, (Dimambro et al.
2007), forest residue (Veijalainen et al. 2007b), agricultural waste (Manios 2004), garden
waste (Brewer and Sullivan 2003), sewage and papermill sludge (Man
˜as et al. 2009) and
livestock manure (Desalegn et al. 2008). These composts contribute to improving the
fertility of agricultural soils (Roe 2001), soils destined for the production of bare root forest
seedlings (Davis et al. 2006), horticultural plants (Fitzpatrick 2001) and the control of
pathogens (Noble and Coventry 2005).
The major disadvantages of these types of composts are the variability in composition
and the presence of pollutants that have the potential to negatively affect human health and
contaminate the water table (De
´portes et al. 1995). Developing countries are not neces-
sarily equipped with centers for treating and composting solid waste. Moreover, the fre-
quent use of certain very heterogeneous organic materials, notably municipal waste, makes
it difficult to attain the reproducibility and quality standards which meet the requirements
for forest nursery substrates. Particular attention must be paid to the use of simple, envi-
ronmentally acceptable composting techniques which are easily accessible to nursery
growers. Little work has focused on the valorization and composting of forest biomass,
268 New Forests (2012) 43:267–286
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particularly branches of fast growing broadleaved species adapted to arid and semi-arid
Recently, pure tree branch-based compost was successfully used for the first time on an
operational scale for the production of forest seedlings and ornamental plants (Lamhamedi
et al. 2006; Ammari et al. 2003). The global use of fast growing genera such as Eucalyptus
and Acacia in reforestation programs for wood production and dune stabilization prompted
us to evaluate the possibility of composting this biomass. There are three principal reasons
why this kind of compost might be useful: (1) to valorize early silvicultural operations
(thinning, pruning), which are generally not profitable given that the harvested biomass has
no marketable value; (2) to decrease the negative impact of eucalyptus leaves on bio-
geochemical cycles and herbaceous layer development; and (3) to find an alternative to the
importation of peat and improve forest nursery cultural techniques for the production of
consistent-quality organic substrates, while creating employment in arid and semi-arid
The objectives of the study consist of (1) studying the feasibility of producing different
composts and substrates from fresh shredded branches of fast growing broadleaved species
(Acacia cyanophylla Lindl, Acacia cyclops A. Cunn. ex G. Don (leguminous trees) and
Eucalyptus gomphocephala DC) (Myrtaceae) which are widely used in reforestation
programs in arid and semi-arid zones; (2) characterising the chemical properties of the
composts at different phases during a complete composting cycle and identifying the
properties that are integral to managing the composting process; (3) comparing the com-
posting process at different times of the year; (4) evaluating the possibility of using the
composts as growing media for seedling production; and (5) classifying composts into
homogeneous groups using principal components analysis.
Materials and methods
Raw organic material
Leafy branches of Acacia cyclops A. Cunn. Ex G. Don (AS) and Eucalyptus gompho-
cephala DC (EG) were collected in Sidi Jaber, an arid bioclimatic zone approximately
80 km northeast of the city of Marrakech, in a forest research arboretum and in a young
coppice forest, respectively. Leafy branches of Acacia cyanophylla Lindl. (AA) were
collected from le circuit de la palmeraie within the urban perimeter of Marrakech. Other
AS branches were collected from trees that had been planted to stabilize the coastal dunes
in Essaouira, 100 km west of Marrakech. These trees were directly exposed to ocean spray.
The foliage:woody biomass ratio, measured using a balance on the shredding platform,
represented, on average, 59, 56 and 47% of the total fresh branch mass for EG, AA and AS,
Creation of the compost piles
Composting was done in unsheltered piles on a concrete surface. Ambient temperature and
precipitation were recorded using a meteorological station installed near the experimental
area. The total composting experiment lasted 11 months. Three different composting
periods of approximately 4 months in length were compared (Table 1). Each period was
characterized by the bioclimatic conditions of one of three seasons (winter, spring and
summer) during the thermophilic stage (T°[45°C). Winter-trend composting extended
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from November 1, 2004 to March 15, 2005, a period when temperatures are generally mild
and cool and atmospheric humidity is high. The spring- (March 30 to August 6, 2005) and
summer- (May 15 to September 20, 2005) trend composting periods were hot and dry. For
each composting period, one pile was prepared for each type of organic material (AA, AS
and EG). The dimensions of the piles were: 1.5 m in width at the base, 3 m in length and
1.5 m in height. The volumes of raw organic material and final compost product were
determined using a cubic-meter frame. Nitrogen, in the form of ammonium nitrate, was
added when each pile was created and when the piles were turned for the first time as
described by Lamhamedi et al. (2006) so that the C/N remained close to 30/1. The piles were
turned when it was necessary to aerate the piles, to adjust gravimetric water content to the
target level of 60% or to adjust pile temperature to the desired range (45–55°C). Optimal
aeration, moisture and temperature levels provide favorable conditions for aerobic degra-
dation of organic matter. Mid-day temperatures were measured at nine locations in each pile
with 90 cm-long thermometers (model 0.79, Pacific Transducers, Los Angeles, CA).
Chemical properties of the composts
The raw organic material was first sampled immediately after shredding. Subsequent
samples were taken 8 days after the start of composting, during the first days of the
thermophilic phase, and on a monthly basis thereafter for the duration of each composting
period. On each sampling date, four composite samples were randomly selected over the
length of the four sections constituting each pile. Each composite sample was a mix of six
samples (2L/sample). The samples were dried at 65°C to a constant weight, finely ground
(100 lm) and shipped to the Laboratoire de chimie organique et inorganique (ISO 17025)
at the Direction de la recherche forestie
`re (Que
´bec) for analysis.
The electric conductivity (EC
) of the composts was determined from filtered extracts
of substrate-water suspensions (1:20) measured with a conductivity meter (model CDM83,
Radiometer, Copenhagen, Denmark), whereas the pH was measured in the supernatant of a
1:4 compost:demineralised water suspension. Effective cation exchange capacity (CEC
was calculated as the sum of the exchangeable bases and the effective acidity (Hendershot
et al. 2008). The exchangeable bases were determined by extraction with 1 M ammonium
chloride. After filtering the sample, the metals were measured using induced coupled
plasma spectrometry (ICAP 9000, Thermo Jarrell-Ash, Franklin, MA). The effective
acidity was calculated from the pH measurement and the aluminum concentration in the
ammonium chloride extract (Espiau and Peyronel 1976).
Table 1 Mean values of the environmental variables, measured during the three composting periods
Composting period Winter-trend
(Nov. 1, 2004 to
March 15, 2005)
(March 30, 2005 to
August 6, 2005)
(May 15, 2005 to
Sept. 20, 2005)
Average temperature (°C)
13.5 26.4 26.6
Average of minima (°C)
5.0 17.0 17.8
Average of maxima (°C)
22.1 35.7 35.4
Precipitation (mm)
73.8 9.6 44.4
Mean value for the period
Cumulative value for the period
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Using the Kjeldahl method, samples were mineralized with sulphuric acid in the
presence of selenium and hydrogen peroxide at 370°C for an hour. Nitrogen content, in the
form of ammonia, was then determined using flow injection colorimetry (Quickchem 8000,
Lachat Instruments, Milwaukee, Wis.). P, Na, Ca, Mg, K, Al, Fe, Mn, Zn, Cu, and Mo were
directly measured in the diluted sulphuric acid solution by inductively coupled plasma
atomic emission spectrometry (model ICAP 9000, Thermo Instruments, Franklin, Mass.)
(Walinga et al. 1995). Total nitrogen (TN) was determined by the Kjeldahl method, dosing
the nitrite and nitrate extracts with a 2 M KCL solution for 30 min and using flow injection
colorimetry (model Quickchem 8000, Lachat Instruments, Milwaukee, Wis.). Total
organic carbon (TOC) was measured by combustion at approximately 1,350°C. The
resulting carbon dioxide was measured by an infrared detector (Analyseur LECO CR-412).
Forest seedling production and measurement of the composts’ physical properties
The two types of Acacia compost were used to produce tree seedlings. EG composts were
excluded because of their high pH values (8.2). Pure AA and AS composts were supple-
mented with 20% peat moss, by volume, to improve their initial pH values. The control
substrate was composed of peat:vermiculite (3:1; vol/vol). Four samples of each substrate
were analyzed for pH and electrical conductivity at saturation (EC
).Carob seeds
(Ceratonia siliqua L., provenance: El Hoceima, Maroc) were scarified in sulphuric acid for
45 min before sowing one seed/cavity into IPL 15-320 containers. The experiment was
composed of three randomized complete blocks. Each substrate was represented by five
randomly distributed containers/block. The experimental design was installed in two
growth chambers (Conviron model PGW-36, Winnipeg, MB, Canada) at 24/18 ±0.5°C,
65/60 ±3% relative humidity (day/night), with a light intensity of 250 lmol m
a photoperiod of 16 h light/8 h darkness. The seedlings were watered twice daily during
the first 3 weeks, then once a day for the rest of the experiment. Seedlings were fertilized
on a weekly basis, with 4 mg nitrogen (N), 0.52 mg phosphate (P) and 2.6 mg potassium
(K), for a total of 104 mg N, 13.5 mg P et 67.6 mg K over the 6month growing season.
The fertilizer solution also contained calcium (Ca), magnesium (Mg) and micro-nutrients.
After 26 weeks, the height and root collar diameter of five randomly selected seedlings/
block were measured. Three of these five seedlings were then delicately extracted from
their respective cavities for destructive sampling. Root length was measured using
WinRHIZO software (Version 2002a, Regent Instrument INC., Que
´bec, QC). Dry root and
shoot mass were determined after oven-drying the tissue for 48 h at 65°C. Final substrate
and pH values were determined for four composite samples. Each composite sample
was a mixture of the substrate in the root plugs of the five seedlings randomly selected
from three blocks.
The physical properties of AA,AS and PV substrates were assessed at the beginning and
end of this experiment. Two containers were selected and randomly filled with the three
substrates (five cavities per substrate). The initial physical properties were directly mea-
sured on the first unseeded container. Carob seeds were sown into the second container and
seedlings were cultivated as previously described. After 26 weeks of growth, the seedlings
were cut at the root collar and the physical properties of the root plugs were measured. The
containers were saturated from below for 24 h prior to measuring the saturated hydraulic
conductivity (K
) with a constant head infiltrometer (head of 5 cm). The water desorption
characteristic curve of each substrate was obtained by equilibrating the container on ten-
sion tables at -6, -15, -30, -50, and -100 cm of water potential (Allaire et al. 2005).
Air-filled porosity (h
) was calculated as the difference between total porosity
New Forests (2012) 43:267–286 271
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) and bag capacity (BC,cm
) corresponding to a tension equal to
-6 cm, which represents half of the cavity height. Total porosity was estimated from the
volumetric water content of the substrate measured at saturation. Easily-available water
content (EAW, cm
) corresponded to the difference between BC and the volumetric
water content at a water potential of -50 cm.
Experimental design and statistical analyses
To study the impact of organic matter (OM) and composting period on the temperature and
chemical composition of the composts at different times during the composting process, a
Principal Component Analysis (PCA) was first performed on the data. The objective of the
PCA was to reduce the number of dependent variables studied. Of the 19 chemical
components measured, 17 (TOC, C/N, TN, pH, EC
, Na, S, P, K, Ca,
Mg, Mn, Al, Fe) were considered in the PCA. Cu and Zn content showed very little
variation. Factors with eigenvalues higher than 1 were retained and a varimax rotation was
performed on the retained factors to simplify interpretation of the axes.
A repeated measures analysis of variance was then performed considering temperature
and each of the retained factors as dependant variables. OM, composting period (CP),
sampling date (D) and their interactions were considered as fixed factors, while pile
(CP 9OM) was considered as a random factor. The correlations among piles (CP 9OM)
over time were modeled with a first order autoregressive matrix (AR(1)). Since there was
no repetition of CP 9OM, only the main effect of D and interactions involving D could be
studied. Effects were considered significant at a threshold of 0.1%. Since all interactions
include D, an analysis by date was performed both to characterize the interaction and
evaluate the composting process with respect to the five dependent variables; temperature
and four first factors of the PCA. Analysis was performed using the MIXED procedure of
SAS software (V9.2, SAS Institute, Cary, North Carolina).
Morphological variables of the carob seedlings were subjected to an analysis of variance
(ANOVA) using the GLM procedure (SAS Institute, Cary, North Carolina). A least sig-
nificant difference (LSD) test at a significance level of 5% was used to compare the means
of each variable. To understand the effects of organic matter and composting period on
chemical composition of the final product, the data means corresponding to the compost
quality on day 128 (3 types of compost 93 periods) were subjected to multivariate
analyses using principal component analysis (PCA). All 19 measured chemical variables
had been previously centred and standardized and were included in the analysis. This PCA
permitted establishment of the typology of the composts by identifying the homogeneous
groups and the factors that describe them. The information about the composts was
summarized using a reduced number of principal components which are implicated in the
majority of the variability (Sena et al. 2002).
Compost yield
Over the three composting periods, yield (final compost volume/initial volume of shredded
raw material) varied between 39.5 and 41.5%, averaging 40.5%. However, in the spring
and summer when it was hot and dry, compost piles needed to be turned more frequently
272 New Forests (2012) 43:267–286
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(eight times vs four times during the winter). Additional water was also required to
maintain pile moisture content during the spring and summer composting periods.
Composting dynamics
During winter-trend composting (Table 1), the three piles reached the thermophilic stage
(T°[45°C) less than 24 h after their creation (Fig. 1a). This stage lasted 75, 60 and
82 days for the AA,AS and EG composts, respectively. Cold temperatures (minimum of
-5°C) in the composting area, in conjunction with aeration of the developing compost
during the fourth turning, contributed to cooling of the piles and a slowdown in biological
activity for approximately 28 days. With an improvement in meteorological conditions, the
stabilization stage resumed. As the piles entered the thermophilic stage, the temperature of
the EG pile remained lower than the two acacia piles for several days. However, the
temperature of the EG pile eventually surpassed that of the acacia piles, and remained that
way for the rest of the composting cycle.
The thermophilic stage during spring-trend composting was achieved within 30 h
after pile creation (Fig. 1b). This stage was maintained for 83, 77 and 110 days for AA,
AS and EG composts, respectively. During summer-trend composting, the themophilic
stage lasted 88, 78 and 130 days for AA,AS and EG composts, respectively (Fig. 1c).
Transition to the cooling stage was progressive, reflecting the maximum daily tem-
peratures registered at mid-day. Peaks of 60°C were reached and maintained over a
period of several weeks for the three compost types during the spring and summer.
Similar to the winter composting period, the temperature in the EG piles during spring
and summer composting remained inferior to that of the acacia piles for several days at
the beginning of the thermophilic stage. Afterwards, higher thermophilic temperatures
were maintained in the EG pile than in the AA and AS piles for the remainder of the
composting process.
Principal Component Analysis of the 17 chemical variables permitted retention of
four factors which explained 85.5% of the total variation in chemical variable dynamics
over the three composting periods. The first factor explained 30% of the total variation
with a strong contribution (0.70–0.95) of TOC, Ca, Mg, Mn, Al, and Fe. This axis
shows that TOC decreased continuously over composting process, while the cations Ca,
Mg, Mn, Al, and Fe increased. Furthermore, with the exception of Mn, these cations
were strongly correlated with the TOC, permitting the evolution of the composting
process to be assessed by measuring the decrease in TOC. The second factor explained
27% of the total variation with a strong contribution (0.61–0.91) of C/N, S, CEC
and P. These variables increased continuously as composting progressed, while C/N
decreased. Except for sulphur, all of these variables were strongly correlated. This axis
reflects the stability of the composts throughout the entire composting process and
indicates that compost stability can be gauged by monitoring the C/N ratio. The third
factor explained 19% of the variation with a strong contribution (0.78–0.85) of pH, Na
and NH
. The fourth factor explained 9.4% of the variation with a strong contribution
(0.88) of EC
The repeated measures analysis of variance performed on these four factors, as well as
the temperature profile of the piles, revealed that organic matter and composting period had
a significant effect on the chemical composition of the compost and pile temperature for all
sampling dates. The interactions (CP 9D; OM 9D and CP 9OM 9D) were highly
significant (P\0.0001) for all dependant variables that were analyzed.
New Forests (2012) 43:267–286 273
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1 102030405060708090100110120130
Temperature (°C)
Time (Days)
1 102030405060708090100110120130
Temperature (°C)
A. cyanophylla
A. cyclops
E. Gomphoc ephal a
November MarchFebruaryJanuaryDecember
Temperature (°C)
1 10 20 30 40 50 60 70 80 90 100 110 120 130
Fig. 1 Temperature profile
during, awinter composting
(November 1, 2004 to March15,
2005), bspring composting
(March 30 to August 6, 2005) and
csummer composting (May 15 to
September 20, 2005). Each point
represents the average of nine
temperature measurements. The
dotted lines represent the
minimum (T
) and maximum
) daily temperature
recorded during the experiment.
Simple arrows indicate turnings
and the double arrows indicate
sampling dates
274 New Forests (2012) 43:267–286
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Chemical properties of the composts
At the start of the composting process, the acidic pH of the organic matter increased to an
average of 7.0 for AA, 7.7 for AS and 8.2 for EG (Fig. 2a). These increases took place
during the first 2 months of composting, eventually reaching a stable plateau near the end
of the composting process. On the last sampling dates (day 128), a slight decrease in pH
was observed.
The shredded AA branches exhibited a mean initial electrical conductivity (EC
2.98 dS m
(mean for the three composting periods), which was high in comparison with
those of AS (1.60 dS m
) and EG (1.31 dS m
). The salinity of the three compost types
evolved similarly over time: a significant decrease of about 50% of the initial value
occurred during the first 8 days of composting, followed by a progressive increase until the
last sampling date (Fig. 2b). The average final EC
values on day 128, for the three
composting periods, were 1.50, 0.76 and 1.40 dS m
for AA,AS and EG, respectively.
The effective cation exchange capacity (CEC
) evolved similarly for all three compost
types, a marked decrease during the first 8 days, followed by a continual increase for the
duration of the composting process (Fig. 2c). Although the average initial CEC
varied among the composts (86, 66 and 54 meq/100 g, for AA,AS and EG, respectively),
the average values at the end of the process were similar for the AA and EG composts
(110 meq/100 g). These values were high in comparaison to that of AS compost with an
average of 90 meq/100 g.
Total organic carbon (TOC) decreased continuously, but remained low during the entire
composting process (Fig. 2d). The average loss of TOC over the three composting periods
was evaluated to be 7.28% for AA, 7.18% for AS and 9.38% for EG composts.
The initial C/N ratio decreased continually during the thermophilic stage (Fig. 2e), the
largest decrease occurred during the first month of composting. Average final C/N ratios
were 14, 18 and 16 for AA,AS and EG composts respectively.
Macro and micro-nutrients
Component analysis of the chemical variables for all sampling dates over the three
composting periods showed that the three compost types were enriched in total nitrogen,
sodium, calcium, magnesium, phosphorus, aluminum, iron, manganese, potassium, sulphur
and nitrate, but were impoverished in carbon and ammonium. For example, TN increased
to about 1.7, 2.2 and 3.3 times its initial concentration in AA, AS and EG compost
respectively. A marked decrease in the ammonium concentration was noted during the first
days of the thermophilic stage. Nitrate concentration varied very little during the active
composting stages. However, a slight increase in nitrate concentration was noted at the end
of the process. The copper concentration remained unchanged at levels below 0.02 g/kg
throughout all of the composting cycles while the zinc level changed little.
Forest seedling production and physicochemical properties of the composts
The addition of 20% peat (v/v) to the AA and AS composts resulted in an appreciable
reduction in pH: from 7.0 to 6.1 for AA and from 7.7 to 7.1 for AS. Their respective EC
fluctuated little at the start of culture, but decreased with irrigation to a value of 0.95 dS
, which is not statistically different from the optimal value of the peat:vermiculite
substrate. Physical analyses showed a high initial porosity and saturated hydraulic con-
ductivity (K
) values, particularly for AS. Furthermore, a drastic decrease in the air filled
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porosity of both acacia composts occurred after 26 weeks of culture, reaching an average
value of 0.15 cm
(Tables 2and 3).
To evaluate the quality and maturity of the composts, seeds of two leguminous species
(Lens culinaris and Cicer arietinum) were sown into containers filled with AA,AS and EG
composts and PV substrate. Germination rates (98 and 87% for L. culinaris and C. ari-
etinum respectively) were very similar among the three types of compost and the
peat:vermiculite control substrate (results not shown).
After 26 weeks of culture, high quality Ceratonia siliqua seedlings were produced in
both the AA and AS composts. The morphological variables (diameter, shoot and root dry
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0 163248648096112128
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0 163248648096112128
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0 163248648096112128
0 163248648096112128
0 163248648096112128
0 163248648096112128
EC1/20 (dS m-1)
CECe(meg/100g)TOC (g/kg)C/N
Fig. 2 Evolution of apH, belectrical conductivity (EC), ceffective exchange capacity (CECeff), dtotal
carbon (TOC) and ecarbon/nitrogen ratio, during (1) winter composting (2) spring composting, and (3)
summer composting. N =4; mean ±SD
276 New Forests (2012) 43:267–286
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mass, shoot and root lengths) of the seedlings produced in AA compost were significantly
superior to those grown on the AS compost (Table 3). However, the shoot and root dry
mass and shoot and root lengths of seedlings grown in AA and AS were significantly
inferior to those produced in the PV substrate. The reduction in growth was estimated to be
39, 28, 29 and 51% in AA and 72, 54, 50 and 56% in AS for shoot mass, root mass, shoot
length and root length, respectively.
Using multivariate analysis to determine the typology of the composts
According to the principal components analysis (PCA) the first three factors explained 90%
of the total variation in the chemical composition of the end product. The first factor alone
explained 42% of the variation with a strong contribution (0.63–0.88) of C/N, EC
, CEC,
, TN, P, K, Mg, Al, Fe, P and Zn. The second factor explained 28% of the variation
with a strong contribution (0.74–0.95) of pH, NH
, S, Mn and Ca. The third factor was
characterized by a strong contribution (0.63–0.81) of TOC, Na and Al and explained
19% of the total variation.
Table 2 Comparison of substrate physical properties (means ±SD) at the beginning and end of 26 week
growing season of containerized Ceratonia siliqua seedlings (air-filled porosity, h
:n=5; easily available
water, EAW: n =5 and saturated hydraulic conductivity, K
(cm cm
) EAW (cm
(cm s
Beginning End Beginning End Beginning End
PV 0.31 ±0.03b 0.25 ±0.01a 0.30 ±0.03a 0.27 ±0.04a 0.11 ±0.02c 0.17 ±0.06ab
AA 0.32 ±0.05b 0.15 ±0.01b 0.31 ±0.01a 0.32 ±0.05a 0.26 ±0.01b 0.12 ±0.03b
AS 0.39 ±0.06a 0.15 ±0.03b 0.25 ±0.04b 0.32 ±0.05a 0.78 ±0.04a 0.23 ±0.02a
In each column, means followed by the same letter are not significantly different at PB0.05 according to
LSD test
AA, Acacia cyanophylla compost; AS, Acacia cyclops compost; PV, peat-vermiculite
Table 3 Comparison of means of morphological variables (±SE) of containerized Ceratonia siliqua
seedlings grown in the two composts and the control substrate, peat-vermiculite at the end of the 26 week
growing season
Root collar Shoot length SHOOT dry Roots dry Roots length
Diameter (mm) (cm) Mass (g) Mass (g) (cm)
PV 4.24 ±0.25a* 19.14 ±1.18a 4.88 ±0.45a 1.34 ±0.13a 95.23 ±11.3a
AA 3.87 ±0.23b* 13.51 ±1.14b 2.97 ±0.38b 0.97 ±0.13b 47.04 ±11.4b
AS 3.28 ±0.28c* 09.48 ±1.17c 1.37 ±0.48c 0.61 ±0.15c 42.04 ±11.3b
In each column, means followed by the same letter are not significantly different at PB0.05 according to a
LSD test
Root collar diameter and shoot length are presented with the average value for the 3 blocks 95 seedlings =
15 seedlings ±SE. Shoot and root dry mass and length are presented with the average value of
3 blocks 93 seedlings =9 seedlings ±SE. The evaluation was made after 26 weeks of growth
AA, Acacia cyanophylla compost; AS, Acacia cyclops compost; PV, peat-vermiculite
* Significant at PB0.1
New Forests (2012) 43:267–286 277
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Figure 3a presents the treatment projections of the first principal component plot,
defined by Factor1 and Factor2, which explain 70% of the total variation. This projection
reveals the presence of three distinct compost groupings (AA,AS and EG), each composed
of three composting periods. On the first axis of this plane salts (cations and anions), EC
and CEC
are plotted against C/N. This axis illustrates that the compost richest in salts
also has the highest EC
and CEC
and the lowest C/N. Thus, Factor1 separated the
composts into two groups. The EG and AA composts rich in salts and the second, the
AS composts with lower salt contents. The correlation matrix illustrates the strong positive
correlation between EC
and Na, K, P and Mg salts. However, the strong negative
Factor2: (28.4 % of total variation)
Factor1: (41.8 % of total variation)
High EC
and pH
High EC and
Low EC
neutral pH
Factor3: (19.3 % of total variation)
Factor2: (28.4 % of total variation)
Fig. 3 Principal component
plots related to the final chemical
characteristics of composts:
afirst plot (F1 vs F2); bsecond
plot (F2 vs F3). EG =
E. gomphocephala,AA=
A. cyanophylla and AS =
A. cyclops.1,2and
3=respectively winter, spring
and summer composting.
(EG3) =E. gomphocephala
compost of the summer
composting sampled at 128 days.
The stars (*) in the plot indicate
the position of the treatments
278 New Forests (2012) 43:267–286
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correlation between Factor1 and C/N ratio led to the conclusion that the AS1, AS2 and
AS3 composts, which all had low salt contents, possessed elevated C/N ratios. This first
factor therefore summarizes the information about the degree of compost stability and
salinity and consequently, fertility.
For Factor2, the correlation matrix showed that pH exhibited a strong positive corre-
lation with Ca (0.80), Mg (0.62), Na (0.68) and Mn (0.84). On this axis, an elevated pH
translates to high concentrations of Ca, Mg and Na, while a low pH reflects high con-
centrations of NH
, S and P. Factor2, defined as the basicity axis, distinguished the
composts with high pH values (three composting periods of EG) from those with low (three
composting periods of AA), or intermediate (AS composts) pH values.
The second principal component plot (Fig. 3b), defined by the Factor2 and Factor3,
which together explained 47.8% of the total variation, clearly separated the winter com-
posts from those of the spring and summer. In addition, the composts from the spring
composting were intermediate, between summer and winter composts. Meanwhile, the AS
spring compost (AS2) was projected close to the origin (centre of gravity of the principal
component plot), indicating its impoverishment in mineral nutrients, relative to the other
composts. The Factor3 revealed the richness of AS summer compost (AS3) in sodium (Na).
This richness is in line with the pH of the compost and the fact that its EC
is higher than
those of AS2 and AS1.
Shredding and composting of leafy branches from forest tree species (AA, AS and EG),
produced composts of satisfactory quality which contributed to high seed germination
rates, were free of toxins and supported the growth of quality seedlings. The volume loss
during the thermophilic phase was slightly higher during the hot and dry conditions of
summer than in the cooler and humid composting periods of winter and early spring. This
result was predictable given the importance of water loss during hot weather and high
frequency of turning (Larney et al. 2000, Larney and Hao 2007). The relatively small
reduction in TOC during the composting process (Fig. 2d) was associated with the com-
position and abundance in lingo-cellulose components whose recalcitrant fraction, con-
sisting of condensed tannins and lignins, retard the decomposition process (Said-Pullicino
and Gigliotti 2007; D’Imporzano and Adani 2007). Condensed tannins (soluble and
insoluble) are known to inhibit microbial activity and fungal growth (Schultz et al. 1992).
Despite the short duration of the stabilization phase, the highest C/N values remained
between 15/1 and 20/1, values considered to be favorable in composts that are ready for
use (Rosen et al. 1993). Figure 2e1, e2 and e3 show that C/N ratio curves are approaching
their asymptotes, suggesting that the compost curing processes are nearing completion. In
the present study, the stability of the compost yield and chemical composition over the
three composting periods assured compost quality and enabled us to envision the possi-
bility of a reliable supply of substrate for forest nurseries. By securing the profitability of
the biomass removed for composting during early silvicultural operations such as thinning
and pruning, more intensive sylvicultural programs can be instituted.
The composting process: evolution of temperature and chemical variables
In our trials, the thermophilic phases lasted 90 days or less, with the exception of the EG
pile during spring and summer composting, which lasted 110 and 130 days, respectively.
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This is comparable to other studies. Sale
`tes et al. (2004) reported a thermophilic stage of
63 days for oil palm (Elaeis guineensis Jacq.) compost. The thermophilic phase lasted
approximately 106 days in the composting of a mixture of nursery waste (rejected seed-
lings, growing media, weeds, grass clippings and dead leaves) and horse manure (Veija-
lainen et al. 2007a), 112 days for a mixture of paper sludge and poultry manure (Charest
and Beauchamp 2002) and 183 days during the composting of olive oil mill sludge
(Manios et al. 2006).
The longer thermophilic phases for the EG piles, compared to those of the acacia
species, may be caused by the higher initial ratio of foliar to woody biomass of the EG raw
material (59%) relative to those of either AA (56%) or AS (47%). Shredded green biomass
is a readily available source of energy whose structure promotes the conservation of heat
within the pile for a longer period (Manios 2004; Manios et al. 2003). However, it is
important to note that the low initial nitrogen concentration of the EG leaves (0.8%),
compared to that of the acacia leaves (AA: 1.6%, AS: 1.1%) probably contributed to
prolonging the thermophilic phase (Wedderburn and Carter 1999; Aggangan et al. 1999).
The addition of nitrogen at the beginning of the process was not effective due to the
important lost of ammonium and nitrate with only a slight increase in total nitrogen in the
first 8 days. This was also reported by Sale
`tes et al. (2004). The low temperature profile of
the EG piles, compared to those of the two acacia species, at the beginning of the ther-
mophilic phase may have been due to the relatively strong acidity of the EG tissue (4.9)
versus those of AA (5.3) and AS (5.5) (Sundberg et al. 2004). This level of acidity is
unfavourable to microbial activity (Rosso et al. 1995), especially in the case of EG. The
abundance of monoterpenes in eucalyptus leaves also contributes to the inhibition of
autotrophic aerobic bacterial activity (Ward et al. 1997). Decomposition of eucalyptus
leaves requires more time than for species such as poplar due to the toxicity of the
allelochemical components to the microorganisms that decompose the litter (Chander et al.
1995). The anatomy of eucalyptus leaves may have also contributed to this result. Their
thick, waxy cuticles constitute a physical barrier to breakdown by microorganisms
(Canhoto and Grac¸a 1999). Osawa and Namiki (1981) showed that the leaf wax of several
eucalyptus species contains powerful antioxydants capable of inhibiting or slowing
microbial activity. It is therefore important to shred the vegetative material as small as
possible. This operation will initiate the rapid breakdown of organic matter by putting the
parenchyma, collenchyma and mesophyll tissues, which are rich in soluble carbons and
nutrients, in direct contact with the decomposing organisms. It is also necessary to
acknowledge the importance of low temperatures in the autumn and winter (Fig. 1a) which
permit a reduction in the length of the thermophilic phase during winter composting as well
as a quicker initiation of the maturation phase.
The four first axes of the first PCA performed on all data for the three composting
periods, in the basis of the Eigen values (Tables 2and 3) and correlation matrix (not
presented), illustrates that the composting process and its dynamics can be reasonably
monitored by three of the 19 variables analyzed, C/N, pH and EC
. These variables are
inexpensive and simple to analyze accurately and in real time in the composting area. By
combining a simple composting process and a simplified and efficient method of moni-
toring, this result would be important for developing countries with limited resources.
Unlike the pattern that is normally observed in compost production (Mustin 1987), little
or no decrease in pH was observed in the first few days following the launch of the
composting process. This was most likely due to the high initial NH
ratio. The low
accumulation of organic acids, given the sluggish deterioration during the transitional
phase, may have contributed to this result. Consequently, the pH of the three composts
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increased continuously over the first 2 months of composting. Although the pH values
obtained by the volume method were slightly overestimated with respect to those measured
by the saturated extract method (Sullivan and Miller 2001), the pH of the AA and AS
composts were close to neutrality, the range deemed satisfactory for nursery growing
media. However, given the elevated pH of the EG compost (pH
=8.2), this compost
should either be mixed with other, more acidic, substrates before being suitable for forest
nursery use (Lamhamedi et al. 2009) or be used for the production of broadleaved species,
which are more tolerant basic conditions.
Both AA and AS are nitrogen-fixing species. The high initial EC
values of their
composts reflected the high mineral salt content (high fertility) of the raw organic materials
(Landis and Khadduri 2008). During the first 8 days of composting, the EC
of the three
types of compost decreased sharply, probably due to the leaching of mineral salts (Dewes
1992). The continual increase in EC
after this period was due to the liberation of salts
associated with the deterioration of organic matter. The final EC
values on day 128
were comparable to EC
values of composted yard waste analyzed in a study by Corti
et al. (1998). These values are in the acceptable range for growing media used for con-
tainerized horticultural and forest seedling production (Bunt 1988). The salinity of the
three types of composts (AA, AS and EG) is therefore not a limiting factor for the pro-
duction of the principal Mediterranean ornamental and forest species (Lamhamedi et al.
Given that the pH values obtained for the three compost types at the end of composting
cycle (day 128) were neutral to basic, the associated CEC
values are comparable to CEC.
The CEC values for AA and EG were within the range for peat moss (100–180 meq/100 g)
(Bunt 1988, Landis 1990). Whereas, the average value for AS compost was lower
(90.11 meq/100 g). These values are interesting given that Harada and Inoko (1980)
proposed a CEC [60 meq/100 g as an index of maturity for city refuse compost. Compost
CEC increases with composting time, therefore providing a greater buffering capacity
against changes in pH (Sullivan and Miller 2001). In the present study, CEC and C/N ratio
were the main variables used to assess compost stability (Muhammad Khalid et al. 2010).
Similar to evolution of the C/N ratio, the CEC curves (Fig. 2c) are also approaching
asymptotic conditions, suggesting that the compost curing processes are nearing comple-
tion (Aparna et al. 2008).
In general, all three composts types possessed a good level of fertility and were char-
acterized by elevated organic matter and total nitrogen contents as well as by high levels of
micro- and macro-elements. The marked drop in NH
([50%) during the first eight days of
composting was probably due to leaching and, to a lesser extent, immobilization in its
organic form in the tissues of rapidly reproducing microorganisms (Bernal et al. 1996, Pare
et al. 1998). Losses by NH
volatilization were very low due to the acidity of the organic
matter at this stage (Sanchez-Monedero et al. 2001). However, nitrate levels increased
slightly during the thermophilic phase due to the inhibition of nitrifying bacteria by high
temperatures (Ko et al. 2008).
Forest seedling production and composts’ physicochemical properties
The suboptimal pH values obtained when the composts were augmented with 20% peat
were still slightly higher than the values recommended for the uptake of the most readily
available microelements (Brady 1974; Lamhamedi et al. 2009). It is unlikely that the high
initial air filled porosity of the A. cyclops compost affected plant performance. Compacting
the acacia composts after 26 weeks of culture resulted in a drastic decrease in air filled
New Forests (2012) 43:267–286 281
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porosity, bringing it below the optimal value of 0.20 cm
(Agnew and Leonard 2003;
Heiskanen 1993). This may have negatively affected root growth and dry mass (Table 3).
However, the final air filled porosity of both acacia composts (15%), was between 11.3 and
20%, a range considered by Bugbee and Frink (1986) to be optimal for the growth of potted
plants. On the other hand, the initial K
values, which were initially very high, particularly
for AS and to lesser extent for AA, are far above the commonly attained values of
0.08–0.12 cm s
. This may have resulted in excessive drainage and some nutrient
leaching. Under our experimental conditions, the seedlings produced in the AA and AS
composts were as vigorous as those grown in the PV substrate. The significant inferiority of
the morphological variables of the seedlings grown in the two composts, relative to those
grown in PV, may be due to their initial high saturated hydraulic conductivities and the
significant reduction in their air-filled porosities (Table 2). It is therefore important to be
familiar with a substrate’s physical properties so that irrigation schedules can be optimized
(Caron and Nkongolo 2004). This is particularly important in the case of composted
substrates, which require a more intensive irrigation schedule at the beginning of the
production cycle (Lemaire et al. 2003).
Compost typology
The projection of the three distinct groups of composts (AA, AS and EG) on the first
principal component plot of the PCA revealed the relationship between the quality of the
end product and the initial chemical properties of its raw materials. This relationship is
very important because it signifies that compost fertility at the end of the composting
process can be predicted from the chemical characteristics of the vegetative matter from
which was formed, which is something that can easily be controlled. The abundance of
salts in the EG and AA composts, as revealed by Factor1 (Fig. 3a), was due to the relatively
high ratio of leafy biomass to woody biomass of their raw materials (EG: 59% and AA:
56%, vs. 47% for AS). Leafy biomass constitutes an important source of nitrogen and
mineral nutrients. Because mineralization in the AA and EG composts was more advanced,
these composts were richer in mineral elements than the AS composts which had relatively
higher C/N ratios. The elevated pH of the EG composts revealed by Factor2 is due to the
chemical composition of their raw materials. The biomass of this forest species, which
used exclusively for reforestation of calcareous soils in North Africa, is very rich in Mg, Ca
and Na (Lapeyrie and Chilvers 1985). Whereas, the homogeneous group comprised of the
AA composts reflects the high tissue nitrogen content of Acacia cyanophylla, a nitrogen-
fixing species (Wedderburn and Carter 1999;Pe
´rez-Corona et al. 2006).
The distinct separation between the composts from the winter composting (AA1,AS1,
EG1) and those from the spring and summer composting, as defined by Factor3, followed
the rate of TOC decrease. The rate of decrease in TOC is a good indication of how well
the composting process is progressing. The projection of the treatments on Factor3
(Fig. 3b) followed the gradient of seasonal temperature increase from the cool temper-
atures of autumn/winter (winter composting with lowest carbon ratio, bottom of the plan),
through the milder temperatures of spring (spring composting, middle of the plan) to the
heat of summer (summer composting, top of the plan). The cool winter temperatures
probably contributed to shortening of the thermophilic phase in favor of more rapid
transition to the maturation phase. However, the high EC
of the AS3 compost, as
revealed by Factor3, is probably due to its Na-rich biomass, which was harvested from
trees directly in the path of the ocean spray on the Atlantic coast.
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This research shows that composting of shredded leafy branches of Acacia cyanophylla,
A. cyclops and Eucalyptus gomphocephala on an operational scale is possible throughout
the year in arid zones. The composts produced were of reproducible quality and suitable
for use as growing media for the nursery production of forest seedlings. In comparison to
substrates from other sources, our approach for producing standardized nursery substrates
constitutes a simplified, integrated and long term viable alternative. Compost dynamics,
stability and quality can be monitored on an operational scale using variables that are
easily measured (C/N, pH and EC), which is very important in countries with limited
resources. Germination of seeds sown in the three composts was uniform and rapid.
Although the two acacia composts assured the production of high quality forest seedlings,
the dry mass, height and root length of the plants produced in these composts were inferior
to seedlings grown in a peat-vermiculite substrate. To improve seedling quality, the
physical and hydrodynamic properties of the composts must be evaluated over a complete
seedling production cycle to determine their degree of stability and to optimize irrigation
and fertilization regimes.
Acknowledgments To the team of employees and research assistants at the Centre re
´gional de la
recherche forestie
`re de Marrakech, Dr. Mohamed Abourouh of la Division de Recherche et d’Expe
tations Forestie
`res a
`Rabat as well as Mario Renaud, Linda Veilleux and Denis Langlois of la Direction de la
recherche forestie
`re de Que
´bec. We are also grateful to Dr. Papaniokhor Diouf for his assistance with the
chemical tests and to Arthur Goussanou and Denis Talbot for their contribution to the statistical analyses.
Financial support for this project was provided to Dr. Mohammed S. Lamhamedi by the ministe
`re des
Ressources naturelles et de la Faune du Que
´bec (project: 112310094) and to Dr. Hank Margolis by the
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... L'approche méthodologique du diagnostic et de la typologie des pépinières, ainsi que les infrastructures indispensables à la modernisation complète des pépinières forestières en Afrique du Nord sont décrites de façon détaillée par Lamhamedi et al. (2000aLamhamedi et al. ( , 2006. Les modalités d' optimisation du compostage des branches et des écorces des essences forestières à croissance rapide en Afrique du Nord pour la confection de substrats et la production de plants d'arganier et de différentes essences forestières dans le cadre de la modernisation des pépinières forestières sont décrites dans nos travaux (Ammari et al. 2007, Bakry et al. 2011, 2013Guedira et al. 2011, Lamhamedi et al. 2000a, 2006. ...
... La fertilisation en pépinière forestière a été optimisée selon les besoins et les stades de croissance des essences méditerranéennes en pépinière y compris celle de la production de plants d'arganier en conteneurs (Bakry 2015, Lamhamedi et al. 2006. Les propriétés physicochimiques des substrats et les teneurs en eau du substrat lors des irrigations ont été également déterminées selon la composition des substrats à base de compost (Bakry et al. 2011(Bakry et al. , 2013Lamhamedi et al. 2000aLamhamedi et al. , 2006. ...
... Résultats & Discussion :Les innovations techniques, technologiques et biotechnologiques développées et mises en application avec succès, tout au long des 20 dernières années dans le cadre de projets de développement de grande envergure, aussi bien pour les différentes essences forestières de l' Afrique du Nord que pour l'arganier sont forts encourageants quant à l'amélioration tangible de la qualité morpho-physiologique et de la croissance des plants d'arganier(Bakry 2015, Bakry et al. 2009, 2012, 2013, Lamhamedi et Gagnon 2003, Lamhamedi et al. 2000, 2006, Mezghenni et al. 2014, Sbay et Lamhamedi 2015a.En effet, les objectifs de la restauration, la domestication et la modernisation de la filière arganier c.a.d. de la semence à la plantation ne peuvent être atteints que par l'amélioration et l' optimisation des différentes composantes clefs de cette filière(Figure 3), notamment l'utilisation des graines et des plants de haute qualité morpho-physiologique, le compostage et la production de substrats(Figure 4) à base de matériaux locaux (branches des essences forestières à croissance rapide, essences secondaires du maquis, écorces des pins, granules issues des déchets des bouchons du liège, etc.) et la modernisation complète des pépinières dédiées à la production de plants d'arganier (infrastructures modernes : ombrières rétractables résistantes aux vents violents, conteneurs, système automatisé d'irrigation et de fertilisation, outils de gestion informatique, standards de croissance, gestion selon les besoins et stades de croissance des plants, etc.).Dans la filière de semences d'arganier, il serait important de se doter de techniques rapides et modernes permettant d'abord de capter la diversité génétique de l' espèce et d' évaluer la qualité des lots et le choix du calibre de semences à utiliser en pépinière, notamment le recours aux rayons X et à la qualification de l'architecture des semences à l'aide du logiciel Win SEED (Figure 5). ...
... Currently, peat moss still the most common substrate used by forest seedlings growers. However, in recent years, due to the increased cost of peat moss, research is being directed toward the reuse of local materials to meet the rising cost of commercial peat (Marfa et al. 2002;Yu and Zinati 2006;Owen et al. 2008;Mañas et al. 2009;Bakry et al. 2012;Ge et al. 2012;Bakry et al. 2013;Heiskanen 2013;Manh and Wang 2014). ...
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Tetraclinis articulata (Vahl.) Master or thuya is facing several constraints to its successful natural regeneration in Morocco. Containerized seedlings plantation is the only method adopted in thuya forest restoration programs and post-transplant water stress produces high seedling mortality after the first summer following outplanting. There is thus a real need to improve nursery seedlings quality, especially enhancing the growth of the root system by improving the water holding capacity of the root plug. Our aim was to assess the effects of clay on the water holding capacity of the growing media and on various morphological and physiological traits of T. articulata seedlings in the nursery. T.articula seedlings were raised in nursery using nine composite substrates; seedlings quality was evaluated according to their morpho-physiological and performance attributes. This investigation determined that a clay content of 20–25% constitutes an optimum for obtaining seedlings with a good root growth potential and high root viability. Excessive clay content in the growing media resulted in water-logged root plug decreasing root growth potential. This investigation found that morphological attribute as Root Collar Diameter and Root/Shoot ratio could be considered good predictors of Root Growth Potential.
... This result is consistent with those obtained in our study (47%) for the seedlings produced in compost-based substrate. Bakry et al. (2013) reported that during the first 5 months of growth, root collar diameters of seedlings grown in compost-based substrate were greater than those of seedlings grown in a peat-vermiculite substrate. When combined with results from the present study, it appears that compost-based substrate can increase diameter growth rates. ...
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In developing countries, or in those countries that do not produce peat, forest soil has traditionally been used as a substrate for cultivation of seedlings in forest nurseries. However, forest soil as a substrate has not been found to produce seedlings of high quality. Additionally, the harvesting of forest soil within forested stands has negative environmental connotations. The objective of this study was to evaluate the use of Acacia cyanophylla–based compost as an alternative growing media to forest soil for the production of cork oak (Quercus suber L.) seedlings in forest nurseries. The experiment was a Randomized Complete Block (RCB) design consisting of four blocks. Each block consisted of fifteen randomly distributed containers for each of the two treatment substrates (forest soil– and Acacia cyanophylla–based compost). Therefore, in total, 120 acorns were examined. Variables related to seed germination, plant growth, and survival were measured. Germination was high, exceeding 90% in both substrates. However, the compost-based substrate had significantly shorter germination times and an increase in the uniformity of the timing of germination. Seedling growth was significantly affected by the type of substrate, while seedling survival was not. As substrates, compost statistically significantly increased the height (39.2 vs. 33.3 cm), diameter (4.5 vs. 3.5 mm), and total biomass (14.7 vs. 10.4 g) of seedlings relative to forest soil. Based on our findings, the use of compost was found to be an attractive alternative to the use of forest soil in forest nurseries, due not only to the environmental benefits, but also due to improvement in seedling quality.
... This result is consistent with those obtained in our study (47%) for the seedlings produced in compost-based substrate. Bakry et al. (2013) reported that during the first 5 months of growth, root collar diameters of seedlings grown in compost-based substrate were greater than those of seedlings grown in a peat-vermiculite substrate. When combined with results from the present study, it appears that compost-based substrate can increase diameter growth rates. ...
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In developing countries, or in those countries that do not produce peat, forest soil has traditionally been used as a substrate for cultivation of seedlings in forest nurseries. However, forest soil as a substrate has not been found to produce seedlings of high quality. Additionally, the harvesting of forest soil within forested stands has negative environmental connotations. The objective of this study was to evaluate the use of Acacia cyanophylla-based compost as an alternative growing media to forest soil for the production of cork oak (Quercus suber L.) seedlings in forest nurseries. The experiment was a Randomized Complete Block (RCB) design consisting of four blocks. Each block consisted of fifteen randomly distributed containers for each of the two treatment substrates (forest soil-and Acacia cyanophylla-based compost). Therefore, in total, 120 acorns were examined. Variables related to seed germination, plant growth, and survival were measured. Germination was high, exceeding 90% in both substrates. However, the compost-based substrate had significantly shorter germination times and an increase in the uniformity of the timing of germination. Seedling growth was significantly affected by the type of substrate, while seedling survival was not. As substrates, compost statistically significantly increased the height (39.2 vs. 33.3 cm), diameter (4.5 vs. 3.5 mm), and total biomass (14.7 vs. 10.4 g) of seedlings relative to forest soil. Based on our findings, the use of compost was found to be an attractive alternative to the use of forest soil in forest nurseries, due not only to the environmental benefits, but also due to improvement in seedling quality.
... Cultivation of seedlings in container nurseries is influenced by several factors, some of which are independent or partially independent of the nurseryman while others can be modified. Among them, the environmental conditions in which the seedlings grow cannot be modified to a large extent (Lea-Cox et al. 2009;Durło et al. 2018), whereas the quality of seeds (Landis et al. 2010;Kaliniewicz and Tylek 2018), organization of procedures and the methods of production (Wesoły and Hauke 2009), selection of trays (Landis 1990;Ruter and vad de Werken 1991;Tian et al. 2017;Sun et al. 2018) and substrates for the cultivation of a given species (Nkongolo and Caron 1999;Abad et al. 2005;Heiskanen and Rikola 1998;Buck and Evans 2010;Bakry et al. 2013;Fornes and Belda 2019) can be modified to obtain better results while carrying out proper irrigation and fertilization (Mathers et al. 2005;Beeson 2006;Dumroese et al. 2015;Stowe et al. 2010). A specifically composed substrate is one of the important elements of tray cultivation in the nursery; in particular, its physical and mechanical properties influence the growth and quality of the produced seedlings (Argo 1998;Bilderback et al. 2005;Banach et al. 2013). ...
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Cultivation of seedlings in trays requires the use of specifically developed substrates. This study presents the results of the analyses of selected physical and mechanical parameters of a peat–perlite substrate, in which seedlings of the Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst), European beech (Fagus sylvatica L.), and pedunculate oak (Quercus robur L.) were grown during a production season. For each species, the substrate parameters changed throughout the production season, substrate dry weight decreased, whereas its compactness increased with time. Independent of the species, the bulk density and total porosity of the substrate changed or deviated from the optimum range, although the values of porosity were close to maximum and those of density were close to the minimum. In certain periods in the V265 trays with beech and oak seedlings, the substrate was characterized by very low water capacity and excessive air capacity. Compactness measured with a cone penetrometer showed, that this parameter might be used for monitoring the substrate properties.
... In addition to possible allelopathic effects, WWB has much smaller particles than those of BM, up to 5 cm, with less water capacity retention; so that its physical structure can contribute to the toxic effect observed in L. sativa. Bakry et al. (2013) observed that plants growing in composts made with wattle residues developed poorly not due to toxic compounds, but due to excessive porosity, gas diffusivity, high water drainage and apparent density of the wattle composts. ...
The main goal of this article is to study the vermicomposting and composting process of black wattle bark bagasse with bovine manure mixed in different proportions and to evaluate if the composts generated have physicochemical and toxicological aspects suitable for its use as fertilizers. The physicochemical tests of the studied residues and their composts demonstrated that bovine manure and black wattle bark bagasse are sources of macro and micronutrient, but none of the composts showed relevant differences between nutrient concentrations. The final pH of the composts remained acidic, varying between 4.6 and 5.80. During composting the maximum temperature reached by the composts was 29.5 °C, reached by the 20% black wattle bark bagasse compost. The germination test and root elongation performed with Lactuca sativa showed that the black wattle bark bagasse and bovine manure presented toxic effects, but the composting process was capable to reduce their toxicity to safe levels in the composts V5 and C5. Chronical and acute toxicity tests revealed no toxic effect of the composts on Eisenia fetida; the same happened with the avoidance test, which indicated negative avoidance of earthworms. Thus, it is concluded that the biotransformation of black wattle bark bagasse in organic fertilizer is viable through composting process and that composts V5 and C5 have adequate physical, chemical and toxicological characteristics for use as agricultural fertilizer. However, application to Cu-sensitive crops should be avoided due to the high concentration of this element on the composts.
Introduction Monitoring the changes in physical and hydraulic properties and stability of growth media due to root growth effects and wetting and drying cycles is important. Wetting and drying cycles can probably change physical characteristics, availability of water, air and nutrients for the plant and, as a result, might affect the growth and yield of the greenhouse plants. The growth period greatly affects the physical characteristics of the growth substrates; therefore, the watering of growth substrates should be managed according to these changes to avoid improper irrigation. Materials and Methods In this study, 14 growth media were prepared from individual substrates with different volumetric ratios. In order to evaluate the changes of growth media over the time (i.e., during consecutive irrigation events) in the greenhouse, 10 wetting and drying cycles were applied on the growth media in the lab. Several physical indicators including easily available water (EAW), air after irrigation (AIR), water buffering capacity (WBC) and water holding capacity (WHC) of the growth media were determined before and after the wetting and drying cycles. Besides, the subsidence, decrease of mass and decomposition of the growth media were determined over the time. Total porosity (TP), bulk density (BD), particle density (PD), pH and electrical conductivity of the mixtures were measured as well. Results and Discussion The pH values in the growth media varied from 5.72 to 6.94. The maximum pH value was related to sawdust- sugarcane bagasse biochar produced at 300◦C vermiculite-zeolite, and wheat straw-vermiculite substrates, and the minimum value was related to the cocopeat-perlite substrate. The values of EC in the growth media varied from 0.21 to 1.43 dS m-1. The highest and lowest EC values among the growth substrates were related to date palm bunches-vermiculite-rockwool and rockwool (0.2)-perlite substrates, respectively. The bulk density (BD) values of the growth media varied in the range of 0.1630.401 Mg m-3. The values of total porosity (TP) of the growth media varied in the range of 64.882.8%v/v. The highest TP was related to the cocopeat-perlite substrate. The TP values of most of the substrates were greater than 70%v/v. The average values of EAW in the growth substrates ranged from 0.123 to 0.272 cm3 cm-3. The highest EAW was related to the sawdust-sawdust biochar produced at 500 ◦C vermiculite-zeolite substrate. The application of wetting and drying cycles increased EAW in most of the growth media. Therefore, it can be stated that the time had a positive effect on the EAW in most of the growth media. The average values of AIR before and after the application of wetting and drying cycles for the growth media varied in the range of 0.0630.240 cm-3 cm3. The highest value of this indicator was observed in the sawdust-date palm bunches biochar produced at 300◦C vermiculite substrate. In all substrates (with the exception of the sawdust-sawdust biochar produced at 500◦C vermiculite-zeolite), the AIR increased after wetting and drying cycles. The range of WHC values before and after applying wetting and drying cycles was 0.4530.699 cm3 cm-3. The highest WHC belonged to the wheat straw-vermiculite substrate. The WHC values of five growth media, including cocopeat-perlite, decreased due to the application of wetting and drying cycles, and the WHC values of nine growth media decreased. The most stable substrate after the wetting and drying cycles was rockwool-sawdust-vermiculite. The effect of time on the quantity of WBC was positive, so that with the application of wetting and drying cycles, the WBC values of most of the substrates increased. In all substrates, subsidence and dry weight reduction were observed after the wetting and drying cycles. These changes were low for the substrates with a high volumetric ratio of inorganic materials. The least change among the growth substrates in terms of decomposition (dry weight reduction) was related to the completely inorganic substrate rockwool (0.1)-perlite (%0.17). The most stable substrate in terms of subsidence after wetting and drying cycles was the rockwool-sawdust-vermiculite, which has a large volumetric ratio of individual inorganic substrates. The highest subsidence was observed in the substrates containing wheat straw (wheat straw-vermiculite and date palm bunches biochar produced at 300◦C wheat straw-vermiculite). The organic matter content in all the growth substrates decreased over time (after wetting and drying cycles). The decrease of organic matter in the substrates can be related to the decomposition of organic materials as a result of wetting and drying cycles. Conclusion The BD, TP, EAW and WHC of the majority of growth media were in the optimal ranges and for some mixtures even better than cocopeat-perlite. Wetting and drying cycles could affect the growth media through several processes such as decomposition of organic compounds, displacement and rearrangement of particles, fragmentation of particles, shrinkage, hardening and subsidence. The growth media with a high percent of organic substrates were unstable as compared with those containing a high proportion of inorganic substrates. In general, the wetting and drying cycles increased the frequency of micropores in the growth media. The wetting and drying cycles positively affected EAW, WHC, AIR and WBC of most growth media. These findings imply that wetting and drying cycles may improve the growth media according to the studied extensive variables. However, it is necessary to study the intensive variables such as hydraulic conductivity, oxygen diffusion and pore tortuosity in the growth media for better evaluation of the impact of wetting and drying cycles as well. Keywords: Air after irrigation, Easily available water, Growth medium, Water retention, Wetting and drying cycles
Green waste compost (GWC) is a value-added product generated by the composting of urban green waste. Although GWC could potentially be used as a growth medium for soilless culture of plants, GWC alone has high salinity, high pH, and other undesirable physicochemical properties. In the current study, we therefore assessed how addition of vermiculite (VMT: 0, 3.5, and 7%) and humic acid (HA: 0, 0.5, and 1 g/100 g) affected the physicochemical properties of GWC and its use as a growth medium for cornflower (Centaurea cyanus L.). GWC modified by the combination of 3.5% VMT and 0.5 g/100 g HA had the best physicochemical properties (bulk density, porosity, water holding capacity, electrical conductivity, pH, and nutrient content) and resulted in the best growth of cornflower in terms of plant height, maximum root length, flower number, and biomass. The results therefore indicate that GWC modified by 3.5% VMT and 0.5 g/100 g HA powder is an excellent soilless growth medium.
Carob (Ceratonia siliqua L.) tree is considered among the most important forest-fruit species native to the Mediterranean region. It has various uses and great valorization potential, all parts of this plant could be exploited as a source of income, as human food or livestock fodder as well as source of raw materials for pharmaceutical, cosmetic, or food industries. Moreover, due to its particular agroecological features, carob tree offers the advantage of growing in poor and unfertile soils in the Mediterranean and Mediterranean-like regions of the world. Thus, carob trees are suitable for the rehabilitation of marginal and sub-marginal areas, helping to compensate for the expanding land desertification in these regions where it can play the role of pioneer and productive species. Carob has been intermittently explored over the last 20 years as a potential tree crop industry in low rainfall areas. The importance of developing the industrial agroforestry potential of the carob tree is hurdled by the lack of options for agroforestry, especially in Mediterranean regions with low rainfall (below 500 mm), and by the need to develop suitable practices for the sustainable management of natural resources. Viable commercial carob cultivation will require mastering efficient farming practices with detailed attention to water requirements and soil fertility. It would improve agricultural productivity in low rainfall areas, help manage water and land degradation, diversify farmers’ incomes, and contribute to the development of export industries contributing to balance the economy of the country. This chapter will provide current knowledge regarding the use of mycorrhizal symbiosis for the improvement of carob culture and productivity in the context of Mediterranean ecosystems. An overview on the multipurpose potential of the carob tree and how spreading its cultivation will benefit people and the environment in marginal areas is highlighted.
Organic amendments added to growing media are claimed to improve plant growth by mechanisms such as providing nutrients, stimulating growth, enhancing flowering and fruiting, increasing beneficial microbes and controlling diseases and pests. However, the claims have received relatively little scientific scrutiny, particularly in containerized plant production. The aim of this review was to evaluate the efficacy of compost-based organic amendments in containerized production horticulture, including composts and vermicomposts produced from plant residues, animal manures, and municipal and industrial wastes; compost teas; and vermicompost teas. Their features and drawbacks, suitability and typical application rates in specific production systems, and knowledge gaps are identified. The variability within and among compost-based organic amendments makes it difficult to generalize about their utility to containerized plant production, however grape marc compost and green waste compost have the widest application in vegetable and ornamental species, respectively.
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Increased environmental pressure is forcing the horticultural industry to look for new growing media in replacement of rockwool and high-quality peat substrates. The objectives of this study were to determine: (1) the effect of different substrates on greenhouse tomato (Lycopersicon esculentum Mill.) yield and root rot caused by Pythium, and (2) the threshold values of some substrate physico-chemical properties for tomato yield and Pythium root rot. Two experiments (fall, spring) were conducted using five substrates. In the fall experiment, yield was related to water availability, as long as aeration was sufficient. In the spring experiment, yield depended on air storage and gas concentrations (O2, CO2) in the substrate because of their low aeration levels. The effect of substrate types and their physico-chemical properties on Pythium root rot varied according to the cultural conditions. Under fall cropping conditions, substrates showing wet and anaerobic conditions favoured Pythium root rot. In these experiments, adequate aeration properties for tomato plant productivity were obtained with a maximum of 30% low-quality peat added to a mixture of sawdust and compost.
The physical quality of peat mixes is in part related to the capacity of the substrate to store and supply air and water to plant roots. During manufacturing, the mixing of various substrate components modifies the substrate characteristics. The objective of this study was to assess the changes in air storage and supply properties caused by varying the particle size of the substrate components. The substrate was composed of 40% wood bark (WB), 50% peat, and 10% coarse gravel (volume basis). Wood bark particle size was varied in a first (0–2, 2–4, 4–8 and 8–25 mm) and a second (1–2, 2–4, 4–8 and 8–16 mm) experiment. When increasing bark particle sizes to 8–25 mm or 8–16 mm, air supply characteristics, as assessed with gas diffusivity measurements, decreased to 0.78 or 0.45 its value for the 2–4 or 1–2 mm average bark particle size. This occurred despite no significant changes in air storage, as assessed from air-filled porosity measurements. Key words: Gas diffusivity, pore tortuosity, air-filled porosity, peat lite mixes, peat substrates
The production of vigorous forest saplings having the required biological and physiological characteristics for insuring survival, growth, and establishment after transplantation constitutes an essential condition for successful forestation programs. For the purpose of improving the quality of saplings produced, the Tunisian forest nurseries were modernized with the introduction of new cultural techniques and the improvement of traditional culture substrates made up of forest litters. These ones present unsatisfactory physical and chemical properties in addition to problems of availability. That justifies the substitution with a compost of woody biomasses locally accessible. For choosing a standard compost substrate that could be used in the various modern nurseries recently installed, five different mixtures of Acacia Cyanophylla Lindl. compost with sand, heat cured clay, and cork granules were evaluated in presence of a control substrate made up of peat (75%), and vermiculite (25%). Seedlings of Aleppo Pine (Pinus halepensis L.) were cultivated in these different substrates during 223 days for the purpose of comparing their nutritional status and their root growth capability, which are considered as indicators of vigor and potential of survival after transplantation. Results obtained showed that the nutritional status of young saplings remained dependent on the composition of the mixture constituting the culture substrate used and its physical and chemical characteristics, especially the density and the pH. Saplings issued from Acacia compost based substrates were inferior to those cultivated on peat-vermiculite only by a lower content of Mn and Zn. For the evaluation of root growth capability, a supplementary 30-day period allowed to observe that saplings raised on Acacia compost substrates (50%) mixed with sand (15 to 35%), heat cured clay (0 to 15%), and cork granules (0 to 30%) offered the best performance in regard to newly initiated roots, their biomass, and their elongation. Acacia composts mixed with either a high sand proportion (50%), or with heat cured clay and cork granules, but without sand, offered a substantially lower performance for all abovementioned growth parameters. The lowest measurements were recorded on seedlings grown on traditional forest litter. In conclusion, a substrate made up of 50% acacia compost, 15 to 35% sand, and 15 to 35% fine particles of heat cured clay and/or cork granules seems to offer the best conditions for producing quality saplings in forest nurseries of Tunisia and neighboring countries.
The article discusses sewage sludge composting on the island of Crete. Pilot tests indicate optimum sludge to bulking agent ratios, effects of replacing green materials with wood chips and variations in compost product quality. The different experimental trials in Crete have been conducted using a variety of local waste derived organic materials for bulking agents, producing satisfactory and promising results for both the composting process of sewage sludge and the quality of compost.