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This study analyzed water and soil quality and environmental impacts of shrimp farming in the southwestern coastal region of Bangladesh. Shrimp farming in the region is very traditional in nature where two culture systems viz. shrimp-rice and shrimponly are being practiced, which are characterized by lower production, repeated stocking, irregular feeding, and fertilizing. Water quality in both farming systems was found suitable for optimum growth and survival of shrimp (Penaeus spp.). The level of 5-day biological oxygen demand (BOD 5 ) in both systems even in canal water was within the recommended level provided by the Government of Bangladesh which is less than 5 mg/l. Therefore, effluents of shrimp farms in the study area did not show any nutrient pollution on the surrounding environment. However, saltwater intrusion has caused many problems like loss of agricultural production, reduced availability of fodder for livestock, and fresh water for domestic uses in the coastal region. The findings of this study confirmed that shrimp farming using saline water have long-term effect of soil salinization. As a result, it poses a real threat toward sustainability of coastal shrimp farming as well as coastal development in Bangladesh.

The study was conducted at the vegetable research farm of the Horticulture Research Centre, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur during the period 2006-2007 to investigate the effects of boron and zinc in presence of different levels of NPK fertilizers on quality of tomato. There were twelve treatment combinations which comprised four levels of boron and zinc viz., i) B0Zn0= 0 kg B + 0 kg Zn/ha, ii) B1.5Zn2.0= 1.5 kg B + 2.0 kg Zn/ha, iii) B2.0Zn4.0 = 2.0 kg B + 4.0 kg Zn/ha, iv) B2.5Zn6.0, 2.5 kg B + 6.0 kg Zn/ha and three levels of NPK fertilizers viz., i) 50% less than the recommended NPK fertilizer dose (50% <RD), ii) Recommended NPK fertilizer dose (RD), iii) 50% more than the recommended NPK fertilizer dose (50% >RD). The highest pulp weight (88.14%), dry matter content (5.34%), TSS (4.50%), acidity (0.47%), ascorbic acid (10.95 mg/100g), lycopene content (112.00 μg/100g), chlorophyll-a (41.00μg/100g), chlorophyll-b (56.00 μg/100g), marketable fruits at 30 days after storage (67.48%) and shelf life (16 days) were recorded with the combination of 2.5 kg B+ 6 kg Zn/ha and recommended dose of NPK fertilizers (N= 253, P= 90, and K= 125 kg/ha). Keywords: Quality of tomato; boron and zinc; NPK fertilizer. DOI: 10.3329/bjar.v35i3.6454Bangladesh J. Agril. Res. 35(3) : 475-488

Buprofezin is an insect growth regulator and widely used insecticide in Malaysia. The present study evaluated the toxic effects of buprofezin on the embryo and larvae of African catfish (Clarias gariepinus) as a model organism. The embryos and larvae were exposed to 7 different concentrations (0, 0.05, 0.5, 5, 25, 50 and 100 mg/L) of buprofezin. Each concentration was assessed in five replicates. Eggs were artificially fertilized and 200 eggs and larvae were subjected to a static bath treatment for all the concentrations. The mortality of embryos was significantly increased with increasing buprofezin concentrations from 5 to 100 mg/L (p< 0.05). However, the mortality was not significantly different (p<0.05) among the following concentrations: 0 (control), 0.05, 0.5 and 5 mg/L. Data obtained from the buprofezin acute toxicity tests were evaluated using probit analysis. The 24 h LC50 value (with 95% confidence limits) of buprofezin for embryos was estimated to be 6.725 (3.167-15.017) mg/L. The hatching of fish embryos was recorded as 68.8, 68.9, 66.9, 66.4, 26.9, 25.1 and 0.12% in response to 7 different concentrations of buprofezin, respectively. The mortality rate of larvae significantly (p<0.05) increased with increasing buprofezin concentrations exposed to 24-48 h. The 24 and 48 h LC50 values (with 95% confidence limits) of buprofezin for the larvae was estimated to be 5.702 (3.198-8.898) and 4.642 (3.264-6.287) mg/L respectively. There were no significant differences (p>0.05) in the LC50 values obtained at 24 and 48 h exposure times. Malformations were observed when the embryos and larvae exposed to more than 5 mg/L. The results emerged from the study suggest that even the low concentration (5 mg/L) of buprofezin in the aquatic environment may have adverse effect on the early embryonic and larval development of African catfish.

In a quantitative assessment of water collected from the midstream of Karatoa river in Bangladesh, 31 water samples were analyzed to assess heavy metals, major ionic constituents and suitability parameters for irrigation usage. The electrical conductivity of all collected samples were within the range of 450 to 1653 µS cm -1 indicating medium to high salinity. Total dissolved solids ranged from 247 to 789 mg L -1 and the samples were rated as fresh water (<1000 mg L -1 ). The anion chemistry in the Karatoa river water was dominated by HCO 3 -and Cl -, which contributed 66 and 31%, respectively of the total anionic mass balance. On the other hand, the cation chemistry indicated that 8 samples showed dominance sequence as Ca > Mg > Na > K, 8 samples as Ca > K > Na > Mg, 7 samples as Ca > Mg > K > Na, 6 samples as Ca > Na > K > Mg and only 2 samples as Ca > K > Mg > Na. Among the studied heavy metals (Fe, Mn, Cu, Zn, Pb, Cr and Ni), the most dominant metal was Fe and Mn. The concentration of Mn in 13 water samples exceeded the surface water quality standard (0.10 mg L -1 ) indicating Mn toxicity. Considering hardness, 6 water samples were graded as moderately hard while the rest 25 samples were graded as hard. As regards to permeability index, 65% of the water samples collected from the midstream of Karatoa river belongs to the unsuitable category.