M.A. Razzak
Department of Fisheries Management, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
A. Nahar
Department of Fisheries Management, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
M. Mirhaj
Department of Aquaculture Systems and Animal Nutrition, Institute for Animal Production in the Tropics and Subtropics, UniversitiH Hohenheim (480), D-70593 Stuttgart, Germany
K. Becker
Department of Aquaculture Systems and Animal Nutrition, Institute for Animal Production in the Tropics and Subtropics, UniversitiH Hohenheim (480), D-70593 Stuttgart, Germany
S. Dewan
Department of Fisheries Management, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
Rice-fish culture, Rice-prawn culture, Water quality parameters
Agronomy Field Laboratory, Bangladesh Agricultural University
Farming System
Experimental Site: The experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University (BAU), Mymensingh during rainy season from July to November, 2007. The experimental site is under the old Brahmaputra Flood Plain Agroecological Zone having non-calcareous dark grey soils of silt loam texture and was situated in a relatively low land area near the deep tube-well of the field laboratory having 0.2 ha in size. The experimental area was divided into 15 plots, each comprising an area of 142 m2 having rectangular in shape. Small water channels (70 em width and 30 em depth) were made between the plots to supply water in the experimental plots. Rainwater and irrigation water from the farm deep tube-well were the sources of water supply to the experimental plots. Each plot had common inlet and outlet in the dikes (height 60 cm, base width 50 cm and top width 40 cm) for regulation of water depth. Nylon nets were fixed around each plot with the help of bamboo poles to prevent the entry of unwanted animals in the plot and escapement of stocked fish. Experimental design: The experiment was conducted in a randomized complete block design (RCBD) with five treatments and three replications for each treatment. The treatments were: rice combined with fish having regular urea fertilization treatment I (T1), rice combined with prawn having regular urea fertilization treatment II (T2), rice combined with fish having supplementary feeding treatment III (T3), rice combined with prawn having supplementary feeding treatment IV (T4) and Treatment V (T5) was kept as control i.e., without fish and prawn. Field management: The experimental plots were ploughed two times using a power tiller. The weeds were removed and the land was then leveled by laddering. A small refuge pond was excavated in the middle of each plot, covering an area of 3m2 with 0.5m depth to provide shelter for fish during low water level and high temperature. A basal dose of fertilizer was applied one day before transplanting according to the recommended dose BRRI, i.e. 150 kg/ha triple super phosphate (TSP) and 75 kg/ha muriate of potash (MP). Urea was applied according to the BRRI, i.e. 220 kg/ha in the Tp T2 and T5 in three installments at 15, 30 and 55 days after transplanting (DAT) of rice seedlings with one-third of the total dose during each application. The seedling of BR 11 were transplanted into the experimental plots at 48 days after seeding (DAS) in alternate row spacing of 35 cm and 15 cm The plant to plant distance in the rows was 20 cm. The alternate row spacing provides enough space for easy movement of fish and to penetrate sunlight in the water between the rows which improves the growth of plankton for fish feed. Stocking and management of fish and prawn: The fingerlings of monosex tilapia (Oreochromis niloticus), common carp (Cyprinus carpio) and juvenile of prawn (Macrobrachium rosenbergii) were released in the experimental plots at 28 DAT and stocked at a density of 1 fish/m2 and 2 prawns/m2 respectively. Fish species were stocked at a ratio of 1:1. The fingerlings and juveniles were kept in a bucket in the experimental plots for about 15 minutes to adjust with the new environment. The healthy and strong fingerlings and juveniles vvere then gradually released into the central ditches. The average initial weight of fish and prawn were recorded at the time of stocking and they were 10.49 g and 1.5 g respectively. Management of fish and prawn Feeding was started five days after stocking. The feed ingredient were thoroughly mixed and made into 4 mm pellets. The feed composition was 50% fish meal, 44% wheat flour, 4% soybean oil and 2% mineral and vitamin premix. The proximate composition of feed on a dry matter (DM) basis was 34.9% crude protein, 12.7% crude lipid, crude ash 13.4% and gross energy 19.5 kJ/g. Feed was provided to the fish @ 6.4 g of feed per kg metabolic body mass per day (g kg-0·8/day) at 2 x maintenance feeding. Feed was provided manually daily at 9 am. Feeding level was adjusted fortnightly based on the prospective fish biomass assuming a metabolic growth rate of 8 g kg-0·8 /day (Frei and Becker 2005). The total amount of feed supplied was 6.5 kg (DM) in each plot. Water was supplied to the plots from the deep tube well and water level was raised gradually ranging from 15-25 cm with the growth of rice and fish. For prawn feed was made into 3 mm pellets. The feed composition was 20% fish meal, 20% wheat flour, 10% meat and bone meal, 20% rice bran, 10% mustard oilcake,15% soybean meal, 4% molasses and 1% mineral and vitamin premix (Bright Fish Premix, Anivet Agro Products Ltd.). The proximate composition of feed on a dry atter (DM) basis was 23.5 % crude protein, 9.4 % crude lipid, crude ash 12.3% and gross energy17.4 kJ/g. Feed was provided daily at 5 pm. Feeding level was adjusted fortnightly based on the sampling. Water quality parameters: Water temperature, pH and dissolved oxygen levels were recorded weekly at 8 am and 3 pm using electronic probes and a portable multi-parameters instrument (Multi 340i, WTW, Weilheim; Germany). In addition, chlorophyll-a level was analyzed using the acetone extraction method (90% concentration) with cellulose nitrate filters (Whatman GF/C). Further water samples were taken fortnightly and analyzed for nitrate, ammonia and phosphate contents by using spectrophotometer (HACK-USA, DR 2010) and reagent of mineral stabilizer, polyvinyl alcohol, nessler for ammonia and pillow NitraVer 6, NitriVer 3 for nitrate and phosVer 3 for phosphate. These analyses were also done in duplicate. Harvesting of rice, fish and prawn: Rice was harvested plot-wise at 125 DAT by cutting the plants at the water level with sickle. For determining rice yields, five samples were taken from each plot randomly placing a 1 m2 frame and cutting the rice plants inside the frames at soil level. The rice sampled was threshed out manually. The grains were then cleaned and sun dried and weighed. Representative samples were taken for determination of the dry matter by drying overnight in a laboratory oven at 105 °C. The straw was also sun dried and the moisture content was determined. The yield data of grain and straw were then adjusted into mt/ha at 14% moisture level. Fish and prawn including weed fish were harvested immediately after rice harvesting, i.e. 98 days after stocking fish fingerlings and prawn juveniles. The fish and prawn were collected from each experimental plot manually after draining out the water from the plots. They were then counted and weighed plot and species wise. Data Analysis: Data are presented as mean values ± standard deviations. Mean values were compared by performing one way analysis of variance (ANOVA), followed by LSD test to detect statistically significant differences between the treatments at p<0.05. The software used for statistical analyses was SPSS, Version 11.5 forMS Windows (Chicago USA).
Bangladesh J. Fish. Res., 13(2), 2009: 121-130
Journal