Rice paddy fields are a major source of methane (CH 4 ) emissions, a potent greenhouse gas. We assessed CH 4 emissions from five existing paddy fields farmed in a snowy temperate region in central Hokkaido, Japan. All fields had continuous flooding and a paddy-fallow-paddy (rice) crop rotation system, but with different amounts of rice straw application. The rice straw application rate in the fields ranged from 0 to 219 g dry matter m −2 . CH 4 emission increased with increasing amounts of rice straw. A peak in CH 4 emission at the end of the reproductive stage was observed in all fields receiving rice straw. When continuous flooding was interrupted by drainage for harvesting, emissions from all fields also dropped quickly. Total CH 4 emissions ranged from 4.04 to 40.8 g CH 4 -C m −2 per growing season. We found that CH 4 emissions (g CH 4 -C m −2 per g dry matter) as per unit (dry matter) of rice straw applied in this study were significantly (P < 0.05) higher than those of calculated reported values, presumably because of the retardation of straw decomposition rates during the winter fallow. There was a significant correlation between rice straw carbon application (SCA) rate and total CH 4 emission in continuously flooded fields (CH 4 emission [g C m −2 per growing period] = 0.486 × SCA [g C m −2 ] − 1.644, r 2 = 0.884, P < 0.05), and emissions were 2-10-fold greater than from fields with no rice straw. The results indicate that the presence of rice straw has a significant influence on CH 4 emissions from paddy fields.

Field experiment was conducted to compare and investigate the concentration levels of heavy metals in leafy vegetables with growth stage and plant species variations on an experimental field near the net house of Soil Science Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh during November 2008 to January 2009. Seeds of spinach (Spinacia oleracea), red amaranth (Amaranthus tricolor) and amaranth (Amaranthus oleraseus) were sown on 14 November 2008. Plant and soil samples were collected at different growth stages, such as at 20, 30, 40, and 50 days after sowing (DAS). The concentrations of lead (Pb), cadmium (Cd), nickel (Ni), cobalt (Co), and chromium (Cr) in plant increased with the age of the plant, but the increase was not linear. The rate of increase of concentration of these metals at 20 to 30 DAS was found lower than that at 30 to 40 DAS, except Cr. Heavy metal content gradually increased at the early growing stage and fall during later stages of growth. The significant differences (P < 0.01) were observed between the mean metal concentrations in the three vegetables species. The Pb and Co concentrations in amaranth were found higher compared to those found in spinach and red amaranth. Spinach exhibited higher levels of Cd and Cr than those of other vegetables. However, the three vegetables did not differ significantly in its Ni concentration. The order of heavy metal level in different vegetables was Cd

Levels of lead, cadmium, and nickel in roadside soils and vegetables along a major highway in Gazipur, Bangladesh were investigated. Soil samples were collected at distances of 0, 50, 100, and 1000 m (meter) from the road. The concentrations of lead (Pb) and nickel (Ni) in soil and vegetables (bottle gourd and pumpkin) decreased with distance from the road, indicating their relation to traffic and automotive emissions. The concentration of cadmium (Cd) was found to be independent of distance from road. There were significant differences in the concentrations of lead, cadmium, and nickel for different plant species and soils at various distances. The heavy metals contents both in the soils and vegetables for every distance from the road was found in the order nickel>lead>cadmium.

The levels of lead (Pb), cadmium (Cd), and nickel (Ni) in spinach (Spinacia oleracea), tomato (Lycopersicon esculentum) and cauliflower (Brassica oleracea) and in the rizosphere soils of the industrially polluted (Konabari, Gazipur; Keranigonj, Dhaka), and non-polluted (Bangladesh Agricultural Research Institute-BARI, Gazipur) areas were studied. Four samples from each area were collected during February 2008. Their concentrations varied with the metals and locations, showing the trend: Ni>Pb>Cd and directly polluted> indirectly polluted>non-polluted soils. The order of the elements in spinach, tomato, and cauliflower and their concentration ranges in µg/g of dry weight were Ni (1.506-0.782), respectively. Similarly, the order of the elements in rizosphere soils of spinach, tomato, and cauliflower and their concentration ranges in µg/g of dry weight were Ni (12.respectively. Lead concentration was higher in tomato, followed by spinach and the least in cauliflower irrespective of the location. Cadmium and Ni concentration were found in the order of spinach>tomato>cauliflower, especially in the industrially polluted areas. Concentrations of metals in vegetable samples were related to their concentration in the corresponding soils. Lead, Cd, and Ni concentrations in the studied vegetables were higher than those found in vegetables from other countries, but they were lower than the maximum level allowed in India. Metal transfer factors from soil to vegetables are found to be significant for Cd, Pb and Ni.

An experiment was carried out in Calcareous Low Ganges River Floodplain Soil (AEZ 12) at Pulses Research Sub-Station (PRSS), Madaripur during Kharif I of 2008 and 2009.The objectives were to evaluate the effect of zinc (Zn) and boron (B) on the yield and yield contributing characters of mungbean (Vigna radiata L. Wilczek) and to find out the optimum dose of Zn and B for yield maximization. There were four levels of zinc (0, 0.75, 1.5, and 3.0 kg/ha and boron (0, 0.5, 1.0, and 2 kg/ha) along with a blanket dose of N20 P25 K35 S20 kg/ha. The experiment was laid out in RCBD with three replications. Results showed that the combination of Zn1.5B1.0 produced significantly higher yield (3058 kg/ha) and (2631 kg/ha, in the year 2008 and 2009, respectively. The lowest yield (2173 kg/ha) and (1573 kg/ha, were found in control (Zn0B0) combination. The combined application of zinc and boron were observed superior to their single application in both the years. Therefore, the combination of Zn1.5B1.0 might be considered as suitable dose for mungbean cultivation in Bangladesh. But from regression analysis, the optimum treatment combination was Zn1.87 B1.24 kg/ha for Madaripur.   Keywords: Zinc; boron; mungbean; yield; yield contributing characters. DOI: http://dx.doi.org/10.3329/bjar.v36i1.9231 BJAR 2011; 36(1): 75-85

A study was conducted in Calcareous Low Ganges River Floodplain Soil (AEZ 12) at Regional Pulses Research (RPRS), Madaripur during the Rabi season of 2010-12.The objectives were to evaluate the effect of Zinc (Zn) and Boron (B) on the yield and yield contributing characters of lentil (Lens culinaris Medic) and to estimate the optimum dose of Zn and B for yield maximization. There were 16 treatment combinations comprising four levels each of Zinc (0, 1.0, 2.0 and 3.0 kg/ha) and Boron (0, 0.5, 1.0 and 1.5 kg/ha) along with a blanket dose of N 20 P 16 K 30 S 10 kg/ha were used. The treatments were arranged viz. The experiment was laid out in RCBD with three replications. Results showed that the combination of Zn 3.0 B 1.5 produced significantly higher seed yield (1156 kg/ha). The lowest seed yield (844 kg/ha) was found in control (Zn 0 B 0 ) combination. The combined application of zinc and boron were superior to their single application. Therefore, the combination of Zn 3.0 B 1.5 may be considered as suitable dose for lentil cultivation in Bangladesh. But from regression analysis, the optimum treatment combination was Zn 2.85 B 1.44 for Madaripur, Bangladesh.

A field experiment was carried out at micronutrient experimental field of Soil Science Division, BARI, Joydebpur, Gazipur to study the effect of foliar application of zinc on yield of wheat (BARI gom-25) grown by skipping irrigation at different growth stages of the crop. The experiment was designed in a split plot design on sixteen treatments comprising four irrigation treatments (regular irrigation, skipped irrigation at crown root initiation, skipped irrigation at booting stage and skipped irrigation at grain filling stages of wheat growth) and four foliar application of zinc (0.0%, 0.02%, 0.04% and 0.06% of zinc). Zinc Sulphate Monohydrate (ZnSO 4 . H 2 O) was used as a source of Zn. The interaction effect of irrigation and foliar application of zinc significantly influenced the yield and yield components of wheat. The highest yield (5.59 t ha -1 ) was recorded in normal irrigation which was identical with skipping irrigation at flowering and heading stage with 0.06% foliar application of zinc. Skipping irrigation at crown root initiation stage had the most negative effect on growth and yield. Skipping irrigation at flowering and heading stage of wheat with 0.04% foliar application of zinc gave the identical yield in regular irrigation with 0.04% and 0.06% foliar application of zinc. Thus, foliar application of zinc played a major role on yield and yield components of wheat at later stages of growth. The response of foliar application of Zn was positive and quadrate in nature. The optimum dose was appeared as 0.04% foliar application of zinc for grain yield of wheat in the study area of Joydebpur, Gazipur (AEZ-28).

Field survey based laboratory studies were carried out to investigate trace elements contents in soils and vegetables collected from industrially polluted and non-polluted areas. The content of four trace elements, such as manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) in four popular vegetables, namely spinach (Spinacia oleracea), red amaranth (Amaranthus tricolor), bottle gourd (Lagenaria vulgaris), and pumpkin (Cucurbita moschata) and the rizosphere soils of the respective crops were collected from three locations viz. i) directly polluted (Kaliakoir, Konabari, Gazipur), ii) indirectly polluted (Zorun, Konabari, Gazipur), and iii) non-polluted (BARI, Gazipur) areas. In all four vegetables, a similar trend in metal contents was observed i.e. directly polluted>indirectly polluted>non-polluted. The Mn and Fe concentrations were found in the order of spinach>red amaranth>bottle gourd>pumpkin, whereas it was little bit irregular pattern for Zn. The Cu concentration was higher in spinach followed by red amaranth and the least in bottle gourd irrespective of the location. Mean concentration of Mn, Fe, and Cu in vegetables from investigated areas were below the recommended level except Zn. However, the higher concentrations of Mn, Fe, Cu, and Zn in the polluted (either directly or indirectly) area indicates that industrial activities, such as discharge their wastes and effluents into the natural ecosystems in most cases without any treatment, thus causing health hazard as well as environmental pollution, especially with heavy metals and organic toxic. Bangladesh J. Agril. Res. 37(3): 515-527, September 2012 DOI: http://dx.doi.org/10.3329/bjar.v37i3.12128