2.1. LocationThe experiment was carried out in the farmers field of Tajeparavillage of Kalapara upazila, Patuakhali district, Barishal division, Bangladesh during winter season in two consecutive years at 2016and 2017. The experimental site was very closer to Kuakata seabeach. The experimental site located at about 21.9861°north latitude and 90.2422°east longitude having only 6 m altitude. The climate is tropical in Kalapara Upazila. The average annual temperature is 25.9°C. In a year, the average rainfall is 2647 mm. Generally, the monsoon starts on May and ends on October; more than 92% of rainfall occurs in these months. April–May is susceptible to storm surges. Winter starts on November and ends on February. The winter is short, excessively dry and rainfall less than75 mm which is lower than the evaporation. Plants enjoy severe drought in the dry season. In wet season (June-November) transplanted Aman is the only one crop and in dry season/Rabi season(December-May) most of the lands remain fallow due to salinity.
2.4. Treatment and design: The experiment was laid out in a randomized complete block design with three replications. There were five treatments: bare soil (no mulch control) (T1), rice straw mulch (T2), blue color plastic mulch (T3), black color plastic mulch (T4) and white (semitransparent) color plastic mulch (T5). The treatments were randomly distributed to the plots in each block. The size of the experimental plot was 4 m3 m. The plots were surrounded by 30cm wide and 10 cm high earthen bunds. One meter wide space was kept in between two blocks.
2.5. Experiment setup three ploughing and two ladderings were done to prepare the experimental field every year. In plastic mulch treatments, soils were covered with a respective color plastic sheet so that evaporation loss of water remains the minimum. Regarding straw mulch treatment rice straw @ around 6 t/ha was spread over the soil surface so that soil could not be visible. Seeds were sown following dibbling method on 12 January 2016 and 10 January 2017 within the 5 cm diameter round-cut hole of the plastic sheet. The hole on the plastic sheet was made by a sharp end wooden stick. The plant spacing was 25x60 cm. For nonplastic, mulch treatments seeds were also sown in rows maintaining above mentioned spacing. Granular insecticide (Furadan 5 g) was given in the field during final land preparation to control soil-borne insects.
2.6. Fertilizer application every plot received equal amount of N, P, K, S, B and Zn @ 200,70, 100, 45, 2 and 6 kg/ha, respectively. The source of N, P, K, S, Band Zn were urea, triple superphosphate (TSP), muriate of potash(MoP), gypsum, boric acid and zinc sulfate, respectively. In all the experimental plots triple superphosphate (TSP), muriate of potash(MoP), gypsum, boron and zinc were applied during final land preparation. Urea was applied in three equal splits at final land preparation, 25 and 50 days after sowing. Regarding plastic mulch treatments urea was applied in the root rhizosphere zone using round cut hole of the plastic sheet. Study locationKuakata sea beaching. Map of the study location.M.A. Haque et al. / International Soil and Water Conservation Research 6 (2018).
2.8. Data collectionCrops were harvested at maturity on 12 May 2016 in first year and 23 May 2017 in the second year. Growth and yield contributing data were recorded from randomly selected 5 plants of each plot. Yield data was recorded by harvesting central 20 plants from each plot. Soil temperature was measured using celcious thermometer from 2 to 4 cm soil depth on 10th March both years. Post-harvest soil was collected from root rhizosphere area and analyzed for determination of pH (Jackson, 1968), electrical conductivity(Petersen & Shireen, 2001) and sulfur (S) contents. 2.9. Data analysis: Data recorded on crop characters were subjected to statistical analysis through the computer-based statistical program STAR (Statistical Tool for Agricultural Research) following the basic principles, as outlined by Gomez and Gomez (1984).