Md. H.R. Khan
Department of Soil, Water & Environment, Faculty of Biological Sciences University of Dhaka, Dhaka 1000, Bangladesh
Acid sulfate soils, Aggregate size, Basic slag, Groundwater, Mustard, pH
Department of Soil, Water & Environment, Faculty of Biological Sciences University of Dhaka
Crop-Soil-Water Management
Soil Collection - Badarkhali and Cheringa acid sulfate soils occur in the coastal old mangrove floodplain areas of Cox’ Baza. For the simulation studies using concrete tanks, bulk soils from the 1st layer (0-20 cm), 2nd layer (20-40 cm) and 3rd layer (40-60 cm) of fallow land (crop production was impossible due to severe acidity and salinity) of Badarkhali and Cheringa series were collected, respectively from Purbapukuria (Badarkhali) and Ringbong Sarishaghata (Cheringa) in the Cox’ Bazar district in Bangladesh. Both the soil series had a silty clay texture and contained yellow mottles of jarosite throughout the studied layers. The second layer was more acidic than the first layer, followed by the third layer. Selected physical and chemical properties of these soil layers were analyzed. Based on the field and laboratory investigations, both soil series were classified into the Inceptisol order, Aquept suborder and Salidic Sulfaquept (Badarkhali series) and Typic Sulfic Halaquept (Cheringa series) Great group, according to the USDA Soil Taxonomy. Preparation of Simulation Tanks The soil samples from 1st, 2nd and 3rd layers were air-dried and crushed into different aggregate sizes to prepare a 60 cm soil bed by arranging the soil layers in the same order as that under the fields in Badarkhali and Cheringa soils. Effects of the basic slag application rate (BS10 and BS20: basic slag 10 and 20 t ha-1), aggregate size (A20 and A30: aggregate sizes of soils, less than 20 and 20-30 mm, respectively) and groundwater level (Gw0: no groundwater and Gw50: with groundwater at 50 cm beneath the soil surface) treatments on mustard (Brassica campestris L.) grown in the two preleached (explained in the next paragraph) ASSs were evaluated in a simulation experiment. The size of the concrete tank used for the study was 0.6 m length × 0.6 m breadth × height 0.8 m, i.e. the inside area of each tank was about 0.4 m2.The absolute control (A0Gw0BS0) treatment of the experiment has been excluded due to having no data on agronomic parameters of mustard which was attributed to the severe acidity and salinity problems of the soil. It is also mentioned earlier that the soil was collected from the fallow land, where crop production was nil. Moreover, the author who had conducted several preliminary experiments on BS and recommended its economic use at the rates of 10 to 20 t ha-1 for the ASSs of Bangladesh. Furthermore, the maintenance of A0 sizes (no till) was not an effective measure for this soil. Therefore, the A20Gw0BS10 (T1) treatment was used as experimental control for the present simulation study. The experiment was conducted in the polyethylene house at the premises of the Department of Soil, Water and Environment, University of Dhaka during October to February, 2003. The experiment was set up in a completely randomized design with three replications. The temperatures during experiment were 25±4°C. About 10 kg of air-dried coarse sand, which was previously treated with tap water followed by 1M HCl, and distilled water was put at the bottom of each of the concrete tanks. Thereafter, the soil layers were placed in the concrete tanks according to the following field arrangement: 1st layer at the top of the concrete tank, followed by the 2nd and 3rd layers. The soils amounting to about 70, 30 and 30 kg from the 1st, 2nd and 3rd layers, respectively, i.e., a total of 130 kg soils with aggregate sizes of <20 and 20-30 mm, were placed in the concrete tanks for the treatments. Some of the concrete tanks were designed with facilities aimed at analyzing the effect of groundwater at a depth of 50 cm beneath the soil surface. All the concrete tanks were heavily coated with cement in order to prevent any release of materials. Prior to the seeding operation, the soil in each tank was leached with tap water of about 10 L m-2 each time and this practice was done for 10 times within a week to remove excess salts, i.e. to increase the initial pH(dry 1:2.5) of the 1st layer from 3.9 and 3.6 to more than 4.5 and to decrease their initial EC values from 1.6 and 1.9 to less than 0.2 dS m-1 for the Badarkhali and Cheringa soils, respectively, during seed sowing. Then to the topsoil in each tank, fertilizer containing N, P and K at the rates of 60, 40 and 40 kg ha-1 as urea, triple super phosphate (TSP) and muriate of potash (MP), respectively, was applied. The full dose of TSP and MP, and half of the urea dose were mixed with soil during tank preparation. The remaining half of urea was applied at 40 days after sowing (DAS) at flower bud initiation stage. The topsoils in the concrete tanks were also subjected to the application of basic slag at the rates of 10 and 20 t ha-1 during soil preparation. Mustard seeds were collected from the Bangladesh agriculture research institute and were sown on the 20th of October’03. At the 10 DAS, the mustard plants were thinned and finally 20 plants were allowed to grow in each tank. The soils in the tanks were irrigated till moistening three times with tap water during rosette, 50% flowering and pod filling stage of mustard. The Gw level was also maintained regularly by using tap water (pH 6.8, EC 0.05 S m-1) when required. The tanks received no rain during experiment.
Thai Journal of Agricultural Science 2007, 40(3-4): 107-117
Journal