Influence of Organic and Inorganic Fertilizers on Floating Bed Cultivation of Okra and Cucumber during Summer Season in Southern Part of Bangladesh

Some trails were carried out with a view to evaluate the performances of organic and inorganic fertilizers on growth and yield of okra (Abelmoschus esculentus L.) and cucumber (Cucumis sativus L.) in floating bed cultivation applying water hyacinth in 2014 and 2015 at Gopalpur union under Tungipara upazila of Gopalganj district in Bangladesh. The single factor experiment was conducted following Randomized Complete Block Design (RCBD) in-volving four treatments with three replications viz. T 1 : control (without organic and inorganic fertilizer), T 2 : cow dung, T 3 : recommended dose of NPK and T 4 : 50% cow dung + 50% recommended dose of NPK. Different growth parameters in respect of okra grown in 2014 and 2015, the longest plant height (171.73 cm and 164.03 cm), maximum number of branches (5.67 and 5.67) and leaves (60.33 and 69.67) were found in the treatment T 3 . Regarding yield parameters, significantly higher number of fruits plant −1 , fruit length (cm), fruit diameter (cm), individual fruit weight (g), fruits weight plant −1 (g) and T 4 , where as the production cost was subjected to lower in T 4 compare to T 3 . However, from the economic point of view, the treatment T 4 i.e. application of 50% cow dung + 50% recommended dose of NPK fertilizers in floating bed cultivation was exposed to be more feasible and suitable as cost effec-tive for the growth and yield of okra and cucumber in the experimental area.


Introduction
Bangladesh today faces the multidimensional effects of climate change in the forms of flood, cyclone, rising sea levels, drainage congestion, salinity in freshwater systems etc. Climate variability makes agriculture in Bangladesh highly vulnerable. It is inferred in the available literatures that crop production would be extremely vulnerable under climate change scenarios, and as a result, food security of the country will be at risk [1] [2] [3] [4] [5].
Floating bed cultivation of vegetable could be one of such measures and an alternate production technology that avoids saltwater intrusion, because it offers new opportunities using indigenous knowledge and techniques that are well adapted to local environmental conditions [6]. But lack of proper knowledge in building technique of floating bed, materials required for bed preparation, thickness of the bed, method of cultivation, dose of organic and inorganic fertilizers and method of application, intercultural operations done that impact on yield of floating bed vegetable production.
Floating beds can be prepared in places where water remains more than six months per year and an abundance of water hyacinth exist. Floating farms in costal districts of Barisal, Goplaganj and Pirojpur in the southern part of Bangladesh, most affected by floods, farmers don't have enough cropping space in terms of access to land, so people have learnt to make the most use of flood water. In this context, a floating agricultural practice was developed to rear plants and crops in floating bed, made of water hyacinth, algae or other plant residues.
The system is traditionally called "dhap" in Bangladesh and "kaing" in Burma, where a floating platform is made of decomposing heaps of water hyacinth, keeping the upper surface stuffed with mud or soil [7]. A scientific method similar to hydroponic or soilless agriculture practice was adopted. With the easily available, locally abundant materials, as water hyacinth (Eichhornia crassipes) and other aquatic weeds, local communities construct reasonably sized floating platforms or rafts on which vegetables and other crops can be cultivated.
The application of cow dung manure and vermicompost increases soil organic matter content, and this leads to improved water infiltration and water holding capacity as well as an increased cation exchange capacity. As per Mandal et al. According to Adegunloye et al. [9] C:N ratio in cow dung manure is an indication that it could be a good source of protein for the microbes which involved in decomposition of organic matter. Manure and urine raise the pH level and accelerate the decomposition of organic matter and termite activity [10] [11]. If inorganic fertilizer, especially nitrogen, is combined with manure, the manure reduces soil acidification and improves the nutrient buffering capacity and the release of nutrients [12]. It is thus important to find out the most potential manure and fertilizer combination that will increase our production and meet our food demand. Inorganic fertilizer supplies sufficient nutrients for growth and development of plant. But increased use of inorganic fertilizers in crop production causes health hazards, create problem to the environment including the pollution of air, water, soil etc. Use of organic manures is essential for proper growth and development of crops. In addition to being a good source of plant nutrients, organic manure improves texture, structure, humus, aeration, water holding capacity and microbial activity of growing media and soil and thus helps to increase the productivity. Organic manure contains all plant nutrients in a relatively small amount. On the other hand, inorganic fertilizers contain large amount of specific plant nutrient in a readily available form. Therefore, inorganic fertilizers in combination with organic manure may lead to better performance regarding growth and yield of the crops.
To increase the vegetables production in dhap, integrated use of organic and inorganic fertilizers has been introduced. So, it is necessary to find out an appropriate dose of organic and inorganic fertilizers to obtain economic yield from floating bed vegetables production. Considering the points in view, the present study was conducted to develop a suitable model for floating bed vegetables production by identifying the combined impact of organic/cow dung and inorganic/NPK fertilizers on the performance of okra and cucumber cultivation during summer season in southern part of Bangladesh.

Floating Bed (dhap) Preparation and Treatments
Matured water hyacinths were collected from the nearby river and canal where it grows profusely. After collecting water hyacinths, a first layer was made with 1.7 m thickness, 1.0 m width and 5 m length. Water hyacinths were again dump on the first layer after 10 days later from the first dumping with 0.8 m thickness . So that required thickness was completed and then the bed was left for decomposition before planting of seedlings.
Bamboos were used as anchorage of floating beds to keep them fixed in a place. The decomposed parts of floating bed, roots of water hyacinth were cutting and put them underneath the seedlings or put the chopped materials on the floating bed 30 cm away from the edge of the bed. Four treatments viz. T 1 : control (without organic and inorganic fertilizer); T 2 : cow dung; T 3 : recommended dose of NPK and T 4 : 50% cow dung + 50% recommended dose of NPK were applied to cultivate okra (Abelmoschus esculentus L.) and cucumber (Cucumis sativus L.) in this study.

Raising of Seedlings and Transplanting on Floating Bed
A small ball like structure was made with decomposed water hyacinth that locally called as "Tema". Treated seeds of okra and cucumber at the age of two day after sprouting were put inside the Tema. Two sprouted seeds were sown in each Tema then put the Tema on seedbed. A hole or pit was made on floating bed before transplanting of seedlings. A plant spacing of 50 cm × 50 cm for okra and plant to plant spacing 80 cm for cucumber were maintained. The seedlings at 14 day old were transplanted in a hole placing in the middle portion of the floating bed in one row. Four treatments were then distributed randomly among each block so as to all treatments were placed once in each block.

Application of Manure and Fertilizers and Other Intercultural Operations
Manure and fertilizers were applied according to the treatments considering the recommended fertilizer dose on the basis of decomposed water hyacinth test value for respective crops [13]. and plant protection measures were done as and when needed especially at the primary stage of seedlings established. Fungicide "Thiovit" and insecticide "Diazinon" were used to control powdery mildew in cucumber and shoot and fruit borers in okra respectively.

Cost Return Analysis
The cost and return analysis of a crop grown in a particular year may not year to year. However, economic analysis was done to find out the most economic treatment applying the combination of cow dung and recommended dose of NPK fertilizers on floating bed condition. All input i.e. seed, bamboo, net, cow dung, fertilizers, boat rent and labor cost were considered for calculating cost of production. But the cost of water hyacinth was not considered. The cost and return analysis was done in details according to the procedure of Iqbal et al. [14].
Net return Gross return Total cost of production = − ( ) Benefit cost ratio BCR Gross return Total cost of production = ÷

Effects on Growth Parameters of Okra
Growth parameters of okra varied significantly (P ≤ 0.05) due to application of organic manure and inorganic fertilizers (Table 1) were found in receiving the recommended dose of NPK denoted as T 3 followed by T 4 treatment i.e. 50% cow dung + 50% recommended dose of NPK. These results were significantly greater than those of the treatments T 1 and T 2 . However, the obtaining results exposed that there were no identical differences among all the parameters in between the treatments T 3 and T 4 . The lowest output in all cases was recorded from the control in all treatments in both the years.
This result might be (found in) due to the combined impact of recommended dose of fertilizers, cow dung and decomposed water hyacinth as organic matter.
Usually, the decomposed water hyacinth and cow dung release the nutrients slowly and steadily into the system and enables the plant to absorb nutrients.
A. B. Mondal et al. Chatto et al. [16] found similar output in their experiment with plant height where they reported that combination of individual organic sources with inorganic fertilizer in equal proportion (50:50), exhibited a beneficial response in plant height. There was an agreement with these results in getting the highest number of branches worked out by Malik et al. [17] adapting the integrated application of organic and inorganic fertilizers. Same trend of findings regarding more number of leaf in fluted pumpkin were reported by Idem et al. [18] under similar condition.

Effects on Yield Components of Okra
The cultivation results of 2014 and 2015 exposed in Table 2 [19] indicated similar findings where they found the maximum fruit length and diameter in combined application of organic and inorganic fertilizer. Ferreira et al. [20] reported that the use of organic and mineral fertilizer significantly increased the yield of okra with the increasing rate of manure and mineral fertilizers.

Economic Analysis
The details of economic analysis of okra production over two years have been shown in Table 3. The total variable cost of production in two years ranged from Tk. 267,000.00 to 429,080.00 among the treatments. The highest cost of production (Tk. 429,080.00) was found in T 3 : recommended dose of NPK fertilizers followed by

Effects on Growth Parameters of Cucumber
Results of vine length, number of branches and leaves of cucumber showed a significant variation (P ≤ 0.05) among different treatments ( Table 4). ceiving the treatment T 4 (50% cow dung + 50% recommended dose of NPK) and the lowest number of branches (6.33 and 5.67) and leaves (48.67 and 57.00) per plant were from the control in the same growing years respectively. No significant differences among growth parameters were found in between the treatments T 1 and T 2 and in between T 3 and T 4 . These results were supported by the work done by Ahmed et al. [21] and Abdel-Mawgoud et al. [22] who reported an increase in cucumber vine length with an increase in nitrogen application.

Effects on Yield Components of Cucumber
Yield and yield components viz. fruit number, length and diameter of fruit, individual fruit weight, fruit weight per plant −1 and yield of cucumber varied significantly with the addition of organic and inorganic fertilizers (Table 5)

Economic Analysis
The economic analysis over two years considering material, non-material and over head costs including harvesting of cucumber were recorded for all treatments on unit bed basis and converted to per hectare have been shown in Table   6. The total cost of production ranged from Tk. 326,660.00 to 388,060.00 among the treatments. The variation was due to different input costs along with the variable cost of organic and inorganic fertilizers. The highest cost of production Level of significance * * * * * *= Significant at 5% level. Means followed by common letter(s) in a column do not differ significantly by DMRT. Here, T 1 = Control, T 2 = Cow dung, T 3 = Recommended dose of NPK, T 4 = 50% cow dung + 50% Recommended dose of NPK, Sales price of marketable cucumber @ Tk. 25,000 per ton. American Journal of Plant Sciences exposed that the treatment T 4 combined with organic and inorganic fertilizers i.e. 50% cow dung + 50% recommended dose of NPK was found to be suitable for greater economic return in cultivating cucumber with the climatic conditions of Gopalganj.

Conclusion
Both of NPK assigned as the treatment T 3 were identically similar with those in receiving the treatment T 4 i.e. 50% cow dung + 50% recommended dose of NPK.
In the economic context, the treatment T 4 was exposed to be more feasible and suitable as cost-effective for the growth and yield of okra and cucumber in floating bed cultivation of that experimental region.