Sanzidur Rahman *
School of Geography, University of Plymouth, 7 Kirkby Place, Drake Circus, Plymouth PL4 8AA, UK
R.J. Parkinson
School of Biological Sciences, University of Plymouth, Plymouth PL4 8AA, UK
Soil fertility; Rice production; Profit function analysis; Bangladesh
Jamalpur, Jessore and Comilla
Crop-Soil-Water Management
Fertilizer, Rice
Location and cropping in the study regions Three of the intensive rice producing areas of Bangladesh, Jamalpur, Jessore and Comilla, were selected for this study. Jamalpur is located within Jamalpur Sadar Thana (central administrative sub-district), in the south-eastern part of Jamalpur district. The study area is 180 km northwest from Dhaka. Jessore is located in Manirampur Thana in the southern part of Jessore district, 290 km southwest from Dhaka. Comilla is located in Matlab Thana in the south-eastern part of Chandpur district, 120 km southeast from Dhaka. An estimated 75% of the gross cropped area was under modern varieties of rice and wheat and 62% was under irrigation in the study regions during the crop year 1996. The cropping intensity (defined as the ratio of gross cropped area to net sown area multiplied by 100) of the sample farms is estimated at 172.8 (183.3 in Jamalpur, 178.2 in Jessore and 148.2 in Comilla region), which is very close to the national estimate of 173.2 for the year 1995/1996 (BBS, 2001). Data and variables The study is based on farm-level data for crop year 1996 collected from three agro-ecological regions of Bangladesh. The survey was conducted from February to April 1997. The specific selected regions were Jamalpur (representing wet agroecology), Jessore (representing dry agroecology), and Comilla (representing both wet agroecology and an agriculturally developed area). A multistage random sampling technique was employed to locate the districts, then the Thana (sub-districts), and then the villages in each of the three sub-districts and finally the sample households. A total of 380 households from 21 villages (174 households from eight villages of Jamalpur Sadar Thana, 100 households from six villages of Manirampur Thana and 106 households from seven villages of Matlab Thana) form the sample for the study. Detailed input–output data were collected for modern varieties of rice produced in a crop year. The dataset also includes information on level of soil fertility determined from soil samples collected from representative locations in the study villages. 2.3. Soil sampling and analysis Data on physical and chemical properties of soils from the selected farmers’ fields were collected to evaluate the fertility status of the soil and to examine inter-regional differences between the study areas. Soils were mapped in the three study areas at series level. Soil series were distinguished following a process of detailed chemical and physical characterization using standard procedures (SRDI, 1991), based on assessment of inherent variability. SRDI (1991) employed ranges and thresholds for key soil parameters (texture, colour, structure, pH, organic carbon, available phosphorus, potassium and iron) to define and map separate soil series. Therefore soil series as mapped were used to select five distinct sampling locations in each region, giving a total of 15 composite soil samples, representing 15 different soil series. Soils were collected from random locations within rice plots within the survey households. Soil sub-samples were collected from the 0–200 mm cultivated horizon at each of 3–5 random locations within a selected plot, and were then thoroughly mixed to give a composite sample. Samples were air dried prior to analysis. As a part of a wider project (Rahman, 1998), soil samples were analyzed for (1) soil organic carbon content, (2) available potassium, (3) available phosphorus, (4) available nitrogen, (5) available sulphur, (6) available zinc, (7) soil texture, and (8) soil pH. In this paper, data are presented for the key soil chemical parameters that are directly modified by routine fertilizer practice and are less subject to inter-season and spatial variability, viz. soil organic carbon content, available phosphorus, available potassium, and available nitrogen. Soil organic carbon (SOC) content was measured using the Walkley–Black rapid titration method. Available phosphorus (P) was extracted using Truog’s extraction method and determined colorimetrically by spectrophotometer. Available potassium (K) was extracted by neutral normal ammonium acetate solution and determined by Gallenkamp flame photometer. Available (mineral) nitrogen (N) was determined using the micro-Kjeldahl method. Full methodological details of all soil analyses are given in PCARRD (1980). Soil organic carbon, available N, P and K concentrations were converted into topsoil mass per unit area (kg ha1 ) assuming a soil bulk density of 1.0 mg m3 for the cultivated soil horizon (0.00–0.20 m).
Agricultural Systems 92 (2007) 318–333
Journal