Abstract: The main objective of this study was to prepare compost using local farm resources such as Date Palm Leaves (DPL) and compare it with the imported peatmoss on seed germination, rate of germination and growth of ornamental plants. The results showed that total number of seeds germinated, rate of seed germination, plant height, number of leaves per plant and the dry-biomass per plant was better in the Date Palm Leaves Compost (DPLC) relative to the peat moss. Based on the preliminary results, it is concluded that farming community and the various research organizations should be encouraged to develop technology for the preparation of composts using local farm wastes resources such as date palm leaves and Phragmites australis rather than importing more expansive peat moss.
INTRODUCTION
Saudi Arabia is one of the leading date producing countries in the Middle East where the number of date palm trees is estimated around 18.20 millions (Annon, 1999). Each date palm tree produces 10-20 leaves per year (Pahsa, 1998). The discarded date palm leaves are a source of many hazards such as fire, host for many insect-pests and diseases. The compost showed significant impact on tree growth and production. The main objective of this study is to make use of this hazardous agricultural waste to useful thing by utilizing Date Palm Leaves (DPL) for the preparation of compost and determine its effect on seed germination and growth of many ornamental plants for landscape development. The compost showed significant impact on plant growth and production (Wang et al., 1984; Hartz and Giannini, 1998; Klock, 1998).
MATERIALS AND METHODS
The study was carried out Agricultural Research Station, Dirab, King Saud University, Riyadh, Saudi Arabia during 2007.
Preparation of Date Palm Leaves Compost (DPLC)
Date palm leaves compost was prepared by following the method described
by Abu-Alfadhal (1970) with some modification. The Dried Date Palm Leaves
(DPL) were cut to 10 cm in length and buried in 2x1 m size concrete pit
with a 1.1 m depth. The compost layers were built in such a way that each
layer was about 25 cm deep. First a layer of 96 kg of dried date palm
leaves was placed in the bottom and then, the desired quantity of a mixture
of ammonium sulfate, trisuper phosphate, fine (100 μ) calcium carbonate
and clay in a ratio of 35:7:35: 100 kg, respectively per ton of dried
date palm leaves was distributed homogeneously. Each layer was sprayed
with 77 L of water having a total salinity of 640 mg L-1 Total
Dissolved Solids (TDS). In all, there were 4 identical layers of DPL,
making the total depth of DPL up to 1 m in height. The compaction of date
palm leaves was done manually at the time of making each compost layer
for proper decomposition. Initially, the compost layers were stirred after
six weeks followed by remixing the compost layers with an interval of
3-weeks. After 6-months, the compost pit was opened. The completely decomposed
date palm leaves (compost) were separated from the un-decomposed part
of date palm leaves which was mainly the hard mid-rib of the palm leaves.
The decomposed portion of the date palm leaves (compost) was used in the
experiments.
Chemical Composition of DPL Compost and Peatmoss
The two composts (date palm leaves compost and the imported peat moss)
were analyzed for carbon, nitrogen, carbon to nitrogen ratio, acidity,
total salt concentration, available nitrate, available ammonium, phosphorous,
potassium, iron, manganese, copper, zinc and ash. Also, the Water Holding
Capacity (WHC) of the composts was also measured. The mean chemical composition
of the DPL compost and peatmoss for the two seasons is given in Table
1.
Germination Experiment
Seeds of four ornamental plants namely Dahlia variabilis,
Tagetes erecta, Zinnia elegans and Cosmos bipinnatus
were placed in trays filled with DPL compost and the imported peatmoss
and then left in the laboratory at room temperature i.e., around 23°C.
The number of seeds germinated and the rate of seed germination were recorded
daily. The experimental treatments were replicated three times. A total
of 50 seeds of each plant were tested in each replication. The experiments
were laid out by following a Completely randomized statistical design.
Growth Experiment
Healthy seeds of four ornamental plants namely, Dahlia,
Tagetes, Zinnia and Cosmos were planted in trays filled with
a mixture of sand, clay and perlite in a ratio of 1:1:1 by volume during
the month of May and June, 2007. The trays were kept in a greenhouse with
inside temperature of 18°C plus or minus 2°C. The seed germination
was complete in a week. Later on, 8 healthy seedlings were transplanted
to 20 cm diameter pots filled with Date Palm Leaves Compost (DPLC) and
peatmoss. The pots were kept in the greenhouse. Later on, the seedlings
were thinned to 5 seedlings per pot after one week and replicated 3 times.
The pots were fertilized at the rate of 150 mg L-1 of compound
water soluble fertilizer with a composition of 20:20:20 with irrigation
water.
| Table 1: | Mean chemical composition of DPLC and peatmoss for two seasons |
Plant growth measurements such as plant height, true leaves number and dry weight of the vegetative growth were taken after 45 days of transplanting during the month of May and June. The plant height was taken from the soil surface to the top of the plant. The plants were dried in open paper bags for three weeks in the laboratory.
Statistical Analysis
The experiments were laid out as a complete randomize design, with
three replications and fifty seeds per replication for the germination
experiment and five plants per replication for the growth experiment.
All the data were analyzed using ANOVA (SAS, 2000) and means were compared
by the Least Significant Different (LSD0.05) according to Steal
and Torrie (1996).
RESULTS AND DISCUSSION
Germination Experiment
First Growing Season
There was no significant difference in the number of seeds germinated
in the DPLC and peatmoss except Dahlia where the germination was
significantly more in DPLC than imported peatmoss with an LSD0.05
value of 4.97 (Table 2). Although, there was an increasing
trend in the number of seeds germinated in the DPLC than peatmoss, but
the difference was not significant at 5% level of significance. This suggests
that DPLC proved better growing medium for seed germination of ornamental
plants than the peatmoss.
The rate of germination was identical in both the DPLC and the peatmoss for all the plants except Zinnia where the rate of seed germination was significantly more in DPLC than peatmoss (LSD0.05 = 0.05). However, for other plants, the trend in the rate of seed germination was higher in DPLC than peatmoss for Dahlia and Tagetes except Cosmos (Table 2).
Second Growing Season
The total number of seeds germinated were significantly higher in
DPLC than peatmoss for all the plants except Tagetes where the difference
was not significant (LSD0.05 = 1.43) (Table 3).
| Table 2: | Effect of DPLC and peatmoss on seed germination and the rate of seed germination during the first growing season |
Means in a column followed by the
same letter are not significantly different by LSD0.05 |
|
| Table 3: | Effect of DPLC and peatmoss on seed germination and the rate of seed germination during the second growing season |
Means in a column followed by the
same letter are not significantly different by LSD0.05 |
|
The rate of seed germination was not affected both by the DPLC and peatmoss except the Tagetes plant where the rate of seed germination was higher in DPLC relative to peatmoss (LSD0.05 = 0.20) (Table 3).
Growth Experiment
First Growing Season
Different types of composts (growing medium) did not affect significantly
the plant height of all the ornamental plants (Table 4).
There was a slight increasing trend in plant height in the DPLC than peatmoss,
but the difference was not significant at 5% level of significance.
Similarly, the number of leaves for all the plants did not respond positively to different types of composts (Table 4). This suggests that different types of composts did not affect the number of leaves of the ornamental plants.
Mean dry-weight per plant was not affected significantly by the different types of composts except Tagetes plant where the dry-weight was significantly higher in DPLC than Patmos`s at 5% level of significance during the first growing season (Table 4).
Second Growing Season
The trend for the effect of DPLC and peatmoss on plant height, number
of leaves and dry weight of vegetative growth was almost identical to
the first growing season except the dry weight of biomass of Tagetes
which was significantly more in DPLC than peatmoss during the second growing
season (LSD0.05 = 0.63) (Table 5).
| Table 4: | Effect of different DPLC and peatmoss on plant height, number of leaves and dry weight of vegetative growth during the first growing season |
Means in a column followed by the
same letter are not significantly different by LSD0.05 |
|
| Table 5: | Effect of DPLC and peatmoss on plant height, number of leaves and dry weight of vegetative growth during the second growing season |
Means in a column followed by the
same letter are not significantly different by LSD0.05 |
|
DISCUSSION
Generally composts are used to enhance seed germination and normal plant establishment especially for the ornamental plants which are sensitive to the growing media. The results indicated that preparation of DPLC using the local resources is economical and also a gate way to minimize environmental hazards due to the land disposal of dried DPL. In the present study, number of total seeds germinated and the rate of seed germination were equal or better in DPLC than the peatmoss (Table 2, 3). This could be attributed to moderate pH, available ammonium and Water Holding Capacity (WHC) and the higher nutrient value of the DPLC than the peatmoss (Table 1). The results agree with those of Burger et al. (1997), who stated that seed germination was better in green plants compost. Similarly, Roe et al. (1997), found that 89.2% germination of seeds was obtained when 16.1% of the sewage compost was mixed with solid waste gardens compost. The low germination in peat moss might due to high available ammonium (Ells et al., 1991). The higher seed germination rate (faster germination) in peat moss in some cases could be due to low ph (might caused scarification), high WHC and low salt concentration (Table 1). Roe et al. (1997) obtained faster germination with peatmoss as compared to compost.
The growth parameters of all four species were identical in both the composts (growing mediums) except for the dry-weight of biomass of Tagetes which was better in the DPLC than peatmoss. This may be due to the fact that both the composts (growing mediums) have some advantages and disadvantages which were stated earlier in results. The results agree with those of Chong et al. (1991), who grew eight species of ornamental plants in mushroom compost and bark mediums. They observed better growth in the mushroom compost than bark. Also, Hartz et al. (1996) obtained better growth for Tagetes in the garden waste compost than peatmoss. But, Aiello and Graves (1997) obtained different result when they used bark compost and peat moss 1:1 by volume.
The lower carbon, carbon to nitrogen ratio, high WHC and the higher ash contents of DPLC is due to high clay content of DPLC. Because clay was added on the basis of total weight of the DPL, but the un-decomposed part of DPL i.e., mainly the hard mid-rib of date palm leaves was excluded. Only the decomposed portion of DPL was used in the experiments.
In conclusion, DPLC is an excellent substitute for peatmoss. but, further studies are required to develop improved methods for the preparation of compost from farm waste materials such as Date Palm Leaves (DPL), Phragmites australis (commonly known as Reed Plant growing on the bank of drainage canals), wheat straw and rice straw on economical grounds.