Bangladesh y. fish. Res., 11(1), 2007: 75-92 ©BFRI
Year-round and rotational freshwater prawn, Macrobrachiailz rosenbergii and paddy farming: soil quality, production, and economics
M.J. Alam*, M.S. Islam, H.K. Pal and M. Karim' Bangladesh Fisheries Research Institute, Brackishwater Station, Paikgacha, Khulna 9280, Bangladesh 'Bangladesh Shrimp and Fish Foundation, House # 47, Road # 23, Block # B, Banani, Dhaka *Corresponding author
Abstract A study was carried out at five upazillas (Dumuria, Fakirhat, Pirojpur sadar, Gopalgonj sadar and Kalia) of five southern districts of Khulna, Bagerhat, Pirojpur, Gopalgonj and Narail to understand the comparative production performance and any effect on soil quality in case of year-round golda (Macrobrachium rosenbergii), alternate prawn-paddy and year-round paddy farming. A direct interview of 55 farmers was taken, using pre- tested questionnaire, and soil samples were taken from selected farms before and after each crop. Among the five upazillas, farmers in Gopalgonj sadar and Kalia are not practicing year-round golda. Rotational golda-paddy farming has been recorded to result in maximum profit, with the highest of Tk. 310,912/ha/year in 2003 at Dumuria. Only paddy farming is less profitable than other two cropping patterns, irrespective of study sites. The nutrient status of soil in rotational golda and paddy farming has been found improved, compared to that of only golda or paddy farming.
Key words: Golda-paddy farming, Economics, Soil quality
Introduction Increase in income from already shrunken agricultural land, particularly low-lying mono crop lands, is essential to reduce rural poverty. In recent years, many farmers in mono crop areas have changed a lot in farming pattern by introducing high priced golda (freshwater prawn, Macrobrachium rosenbergii) alternating with boro cultivation. Since late eighties, when there were possibly only a few thousand golda farms converting only a few hundred hectares, the golda farming has gained significant popularity. The area of golda farming has gradually extended from 6,000 ha in 1994 (Chanda and Kandker 1994) to some 30,000 ha in recent years (prs. comm., National Shrimp Cell, Department of Fisheries). Freshwater prawn farming in Bangladesh has a number of socio-economic advantages over marine prawn farming. Unlike the marine prawn farms, which are normally large (average size above 10 ha or 25 ha) and often operated by non-resident M.J. Alam et al. owners, the golda farms are mostly small (average size is less than an acre) and operated by the landowners themselves. Golda farming can be and in many cases actually is well- integrated with paddy production, horticulture and aquaculture of certain species of fish. In fact paddy production in golda ghers (farms) is usually higher than in open bills. The benefits of rice-fish culture, as a low investment entry level technology for resource-poor farmers, have been demonstrated in Bangladesh (Gupta et al. 1998). It has been observed frequently that total farm output increases through the inclusion of suitable fish and/or prawn in rice fields (Roy et al. 1991, Cai et al. 1995, Alam et al. 2006). The culture of golda prawn has apparently no conflict with agriculture. Located away from the sea, the golda farms are not usually vulnerable to cyclones or tidal bores, which almost every year cause damages to marine prawn farm infrastructures and the valuable prawn crops. Besides, golda is not susceptible to the prevailing white spot virus disease that causes huge economic losses to the marine prawn and the farmers. Although golda is a freshwater species, it can survive and grow normally in salinity up to 8 ppt salinity. The opportunity for horizontal and vertical expansion of golda farming is, therefore, enormous. For all these reasons, golda culture is socially more acceptable and technically and economically more viable and sustainable. In recent years, it has been generally observed in golda-boro paddy farming areas that (i) many Golda-Boro fields during the Boro season remain totally or partially fallow, (ii) During the Boro season, many farms are seen to have only scattered patches of boro paddy plants with no or very little care, (iii) many farmers linger prawn production even beyond March to allow the under grown prawn to grow bigger, neglecting or altogether skipping paddy cultivation, (iv) some farmers have intentionally switched over to year round prawn farming skipping paddy cultivation for higher economic gains. During the last two years or so, another situation has arisen. Some farmers have started farming golda prawn with over-wintered juveniles. They keep late season prawn fry in nurseries and use them for raising an early crop from February to May instead of paddy. In this system, the farmers get an opportunity to easily raise the usual traditional crop of prawn from July to December, significantly increasing income from their land. However, questions may arise whether keeping land inundated under water all the time or most of the time is creating any adverse effect on soil quality and productivity. Suspicions also may be there whether prawn production year after year without any crop rotation is all sustainable. With this prevailing background, the present study was conducted during 2004-05 in selected five golda farming districts of southern Bangladesh, aiming at understanding any changes in productivity in year-round golda farming, with those of prawn-paddy alternation, in terms of production, economics and soil quality.
Materials and methods Based on the concentration of golda/prawn farming activities, five study areas were selected, one from each of southern districts of Khulna, Bagerhat, Pirojpur, Gopalgonj and Narail. The study areas were Dumuria upazilla of Khulna, Fakirhat upazilla of
76 Year-round and rotational prawn & paddy farming
Bagerhat, Sadar upazilla of Pirojpur, Sadar upazilla of Gopalgonj and Kalia upazilla of Narail district. From the five selected upazillas, a total of 55 farms and farmers were selected, considering year round prawn, alternate prawn-rice and year round rice cropping pattern, to collect information on management, production and economics (Table 1). For each type of cropping pattern, three farms were selected to collect soil samples. The sampling scheme of soil is given in Table 2.
Table 1. Farming pattern and number of farmers contracted and interviewed in selected study sites
Number of farmers interviewed Farming pattern Pirojpur Gopalgonj Fakirhat Dumuria Kalia Sadar Sadar Year-round prawn 5 5 5 NA NA Crop rotation 5 5 5 5 5 (Paddy and prawn) Rice only 5 5 5 5 5 NA = cropping pattern not available
Table 2. Scheme of soil sampling for different cropping pattern at different study sites
Galda-paddy rotation Year-round golda Only Total soil paddy sample Upazila/Thana End 1st End paddy End galda End 2' crop End of crop (May- (Nov - Dec) paddy (May) (Dec) June) 3 farms x 2 3 farms x 2 3 farms x 2 3 farms x 2 2 farms x Fakirhat 28 samples samples samples samples 2 samples Dumuria do do do do do 28 Pirojpur sadar do do do do do 28 Kalia do do NA NA do 16 Gopalgonj sadar do do NA NA do 16 Total samples 30 30 18 18 20 116 NA = cropping pattern not available
A traditional survey method of direct interview from the selected farmers was followed, using pre-tested questionnaire. Attempts were made to collect data and information prawn-rice production and economics under different cropping pattern and management systems for 2002-2004. Soil samples were collected at a depth of 0-15 cm from the surface. The soil samples were collected in two installments. Initially, before the specific cropping pattern starts (December'04) and then finally after harvesting (May'05). Soil samples were collected from each selected farm of different sites and cropping patterns. Collected samples were dried in room condition, ground, and then passed through a 0.5 mm sieve to separated and discard any gravel, pieces of plant root, leaves, etc. Then adulterate free soil samples 77 M.J. Alam et al. were kept in air-tight plastic bags with proper labeling for subsequent laboratory analyses. Prepared and labeled samples were sent to Soil Resource Development Institute (SRDI, Khulna and Regional Laboratory, Dhaka) to analyse for the parameters of pH (reaction), salinity (EC @ milimose/cm), organic matter (%), potassium (miliequivalent/100 g soil), total nitrogen (%), phosphorus (ug/g soil), sulfur (ug/g soil) and zinc (ug/g soil).
Results and discussion
Management, production and economics of different cropping pattern More than 80% of farmers follow the extensive method and the rest follow improved extensive method of farming. The farmers in Khulna, Bagerhat and Pirojpur areas practice year round prawn, alternate prawn-rice and rice farming, respectively. But in Gopalgonj and Kalia sites, farmers practice only alternate prawn-rice and only rice types. Study site-wise production and economic returns, from year-round prawn, alternate prawn-paddy and only paddy farming, in terms of per hectare yield, total cost, gross profit and net profit are presented in Tables 3a - 3e.
Year-round prawn farming In this method, golda are cultured round the year. Farmers stock the galda post- larvae (PL) in their farms at a density of 22,000 - 29,000/ha. PL are fed at irregular basis. In most of the sites, farmers culture 'golda' (Macrobrachium rosenbergii) and 'bagda' (Penaeus monodon) concurrently whole the year, as bagda become marketable size within 3.0 - 3.5 months and golda is more disease resistant than bagda. The yield of golda per hectare ranged from 302.03-428.57 kg in Fakirhat, 100-163.54 kg in Pirojpur sadar and 755.5-879.18 kg in Dumuria (Table 3a-3c). The highest yield (879.18 kg/ha) has been recorded in Dumuria in 2003 and the lowest (100.00 kg/ha) in Pirojpur sadar in 2002. The total cost of the farming was Tk. 112,036-129,423 in Fakirhat, Tk. 23,958-95,989 in Pirojpur sadar and Tk. 179,947-211,543 in Dumuria (Table 3a-3c). The net profit of prawn farming of the same sites was Tk. 135,185-151,426, 19,792-25,909 and 149,759-208,827, respectively (Table 3a-3c). The highest profit (Tk. 208,827/ha) from year round golda was obtained in Dumuria in 2003 and the lowest (Tk. 19,792/ha) was in Pirojpur sadar in 2002. During the production period, farmers followed partial harvest and partial stocking. Accordingly, golda farmers had a flow of income from golda culture round the year. This farming system has been practiced in Fakirhat, Pirojpur sadar and Dumuria upazilas. The yield of golda were dependent on various factors such as stocking density, feed, fry quality, availability of PL in time, technical knowledge, fund, disease, water quality management, training, high price of snail meat and golda PL, security, etc. Some particular issues in golda farming sites were poaching, prawn poisoning and diseases. Number of livestock was varied from site to site and year to year. No. of livestock of the year round prawn farmers were 1-6 hens with some chicken and 1-10 cows, respectively.
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