抄録
Crop productivity and soil management are dependent on and also affect soil fertility. Farmers apply fertilizer to boost production, but over time this can also lead to chemical imbalances in the soil, such as the accumulation of toxic elements or soil acidification, that reduce crop yields and cause farmers to react by increasing fertilizer application rates. Having observed this phenomenon in Bangladesh, I undertook the study reported herein in two districts of Bangladesh, where the main crop grown was potatoes in one district and rice in the other. The objective of the study was to evaluate soil fertility, nutrients, and organic matter. Ten samples were collected, one at each depth of 15 cm and 85 cm from five sites, three in Munshiganj and two in Comilla. The main soil textures were described and a suite of chemical properties was analyzed in the laboratory. The soil textures were silt clay loam to clay loam. The topsoil samples were strongly acidic to slightly acidic, with pH values ranging from 4.37 to 5.64. The cation exchange capacity (CEC) of the soil samples were high, ranging from 25.4 to 34.8 cmolc kg-1. In general, hig-CEC soils do not need to be limed as frequently as low-CEC soils; however, the low pH values at these sites suggest that liming is required to achieve optimal pH values. Exchangeable sodium was high, ranging from 5.85 to 76.72 cmolc kg-1. Exchangeable calcium was low, ranging from 1.21 to 2.42. Exchangeable sodium percentage (ESP) levels were higher than 15%, indicating that the soils would be prone to dispersion, poor water infiltration, potential sodium toxicity to plants, and calcium deficiency. Soil organic carbon and total nitrogen content in topsoil samples ranged from 12.11 to 19.21 g kg-1 and 1.35 to 2.25 g kg-1, respectively. Overall, these results indicate that the soils have received excessive application of chemical fertilizer and that soil fertility had declined as a result through sodium toxicity and calcium deficiency. Regular soil sampling and communication of recommended application rates to farmers, as well as general awareness-raising activities on the subject of soil fertility, might help reduce the excessive application of fertilizer and lead to better soil fertility.
