Effect of Water-hyacinth Compost on Physical, Physico-chemical Properties of Soil and on Rice Yield
A pot experiment was set to find the effect of compost prepared from water-hyacinth on the experimental soil properties and on rice (BR-11) yield. Two months were needed to stable C/N ratio to 8 of water-hyacinth by decomposing in gunny bags. The compost has a positive effect on the formation of microaggregate of the soil. Water holding capacity also increased significantly with increasing content of water-hyacinth in the soil. Tremendous changes in cation exchange capacity were found with increasing application of water-hyacinth compost and it found 23.75% higher than the control at highest content of water hyacinth compost treatment. On the other hand, non-significant changes in pH occur with the application of the compost. Grain yield of rice also increases with the application of water-hyacinth compost in the soil and the highest 8.13% yield increase was obtained.
Due to extensive and improper use of chemical fertilizers in the soil, our
soil is degrading to an alarming level, causing an imbalance in the ecosystem
and environmental pollution as well. To avoid these adverse effects and also
for sustainable agriculture, one should rely on ecological oriented resource
conserving technologies. On the other hand, organic matter contents of soil
play a major role in natural ecosystems and extensive agriculture (Paul, 1984).
In humid tropical region, high temperature and rainfall hasten the decomposition
of organic matter. As a result organic matter need to be added in the soil frequently
in tropical region. In Bangladesh huge amounts of water hyacinth are found in
the lakes, ponds and rivers causing problems in navigation, fisheries as well
as deep-water rice production but water-hyacinth could be use as an effective
source of soil organic matter. If the organic residues added to the soil without
being well decomposed it will adversely affect plant growth by producing phyto-toxic
compounds (Cocharam et al., 1977; Linch, 1976). In this experiment, compost
was prepared from water-hyacinth to find their effect on physical and phsico-chemical
properties on the experimental soil as well on rice yield.
Materials and Methods
A pot experiment was set up in a net house at Department of Soil Science, University
of Dhaka, during 1992-93 using rice (BR-11) on sandy loam soil. The soil was
dried in the air, ground and passed through a 2mm sieve. Water-hyacinth plants
were collected and cut into pieces and then put in gunny bags. The bags compactly
filled having their mouths tied up with ropes. Afterwards, the bags were put
together in a shady and upland area and allow them to decompose for a period
of 2 months. The gunny bags were used to ensure that the initial anaerobic fermentation
temperature was remained high enough to promote the activities of the thermophiles
(Stutzenberger et al., 1970) and to destroy the pathogens on the other
hand (Rashid, 1998). The bags were watered from time to time to keep them moist
and when the bags showed sign of rotting the contents were transferred into
new bags. After the stipulated time, sample were dried in the air and pulverized.
The carbon and nitrogen contents of the compost were determined. Organic carbon
was determined by the wet oxidation method of Walkley and Black as outlined
by Jackson (1973) and total nitrogen was determined by Kjeldahl method (Black
et al., 1965).
In the experiment, the treatment combinations were as follows:
||Soil +300g Water-Hyacinth Compost (W.H.C.)
||Soil +500g (W.H.C.)
||Soil +1000g (W.H.C.)
There are five replications of each treatment. Six kg soil was taken in the
plastic pots and required quantity of powdered compost was added to each pot.
After eight months of incubation the following physical and physico-chemical
properties were analyzed. The mechanical composition was determined by hydrometer
method (Bouyoucos, 1962). The pH was measured by a glass electrode pH meter
and water holding capacity by a pressure membrane apparatus at 0.3bar. Cation
exchange capacity was determined by the Walkley and Black's rapid titration
method (1934). Microaggregate analysis was carried out by the method described
by Day (1965). The method was same as particle size analysis without using any
dispersing agent and mechanical dispersion. Only 2 hours of mechanical shaking
was used. Index of aggregation was calculated from the data of microaggregate
analysis as suggested by Baver and Rhoades (1962).
After the determination of physical and physico-chemical properties of the experimental soil from each treatment, the pots of each treatment were prepared for rice (BR-11) production. Nitrogen, potassium, phosphorus and sulphur were applied at the rate of 45, 60, 40 and 10kg ha-1, respectively as basal doses. Next, five weeks of old rice seedlings were transplanted at the rate of two hills per pot. Rice was harvested at 110 days after transplantation and different agronomical parameters were determined.
Results and Discussion
In this experiment, the C/N ratio of water-hyacinth fell rapidly to 8 within
two three months and remains more or less stable. It was found (Table
1) that initially, the nitrogen content of water-hyacinth was rather higher
(1.94%). This could be due to plants used were young and more succulent, this
will cause higher nitrogen content in plant (Alexander, 1977) as well as in
|| Carbon and nitrogen content and C/N ratio of the compost
The state of aggregation of soil increases significantly with increasing water
hyacinth compost in the soil (Table 2). This was due to the
fact that the state of aggregation increases with increasing soil organic matter
(Martin et al., 1955).
The degree of aggregation significantly differs among the treatments (Table
2). It was 27% higher than the control where 1000g of water hyacinth was
used per pot. Rashid and Iftekhar (1992) also reported that the degree of aggregation
of soil increased due to water hyacinth compost. There was also positive correlation
between degree of aggregation and organic carbon content in the soil among treatment
means. Water holding capacity also increased due to addition of water hyacinth
(Table 2) and similar results were also obtained by Rashid
and Iftekhar (1992) and Kelling et al. (1977).
||Mean values of state of aggregation, degree of aggregation,
dispersion factor of the experimental soil with standard deviations (±)
as influenced by water-hyacinth compost.
||Mean values of water holding capacity, cation exchange capacity,
organic carbon and pH of rice (BR-11) with standard deviations (±)
as influenced by water-hyacinth compost.
||Mean values of fresh weight of grain and straw and number
of panicle initiation of rice (BR-11) with standard deviations (±)
as influenced by water-hyacinth compost
|Treatments not followed by the same letter(s) are statistically
significant at p=0.05 (Duncan test).
T1=Control, T2= Soil +300g W.H.C., T3=
Soil +500g W.H.C., T4= Soil +1000g W.H.C.
Water hyacinth compost may improve water holding capacity in two ways: firstly,
the particles of water hyacinth may have a direct effect as organic particles
themselves have a high water holding capacity; secondly, by influencing the
physical properties of soil such as bulk density, porosity etc.
Cation exchange capacity increases markedly with increasing the content of
water-hyacinth and it was found 12.30, 20.09 and 23.75% higher then control,
respectively. Very slight change in pH was obtained with increase in the content
of water hyacinth. Fresh weight of grain increases slightly with increasing
content of water-hyacinth compost in the treatments. It was 4.42, 6.45, 8.13%
higher than control at T2, T3, T4 treatments
respectively (Table 3). In case of fresh weight of straw,
highest weight was found 46.97g/pot at the treatment T4 and lowest
weight was found 45.83g/pot at T1 treatment. Therefore, the highest
yield increases was found 2.48% comparing the treatment T4 with T1.
It has been found (Sarwar et al., 1998, 2000) that biofertilizer has
positive impact on rice farming which also support the present experimental
From the experiment, it can be concluded that water-hyacinth compost improve the physical and physicochemical properties of soil. Rice yield also increases slightly with water hyacinth content in the soil. Therefore, water hyacinth can be a very good source of organic fertilizer for sustainable agriculture.
The authors are grateful to Prof. Dr. G.H. Rashid of the Department of Soil,
Water and Environment for his interest, encouragement and necessary help to
carry out the research successfully.
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