Around 7,000 soil-burning brick kilns use over 1.27 billion cubic feet of topsoil every year
Unplanned urbanization and growing number of brick kilns are rapidly depleting Chittagong's topsoil, wreaking havoc on farmland fertility.
According to the Bangladesh Brick Manufacturing Owners' Association, around 7,000 soil-burning brick kilns produce approximately 25 billion bricks every year, using over 1.27 billion cubic feet of topsoil.
According to the Department of Agricultural Extension (DAE), as many as 806 brick kilns are now operating in five districts in Chittagong division, with 410 in Chittagong city, 83 in Cox's Bazar, 113 in Noakhali, 107 in Feni, and 93 in Lakshmipur.
Topsoil depletion has reached such an alarming rate that it made the agenda at the Chittagong Divisional Development Coordination Committee meeting on January 23, held at Chittagong Circuit House.
In line with the meeting’s decision, the Divisional Commissioner's office wrote a letter to the DAE to submit a report citing ways and means to prevent further topsoil depletion.
Apart from coming up with a set of recommendations, the DAE explained the reasons for topsoil loss in the Chittagong and Comilla regions.
According to the report, fertile top layers of farmland are ruined by the removal of topsoil used to manufacture bricks.
Oblivious to the long-term detrimental impact, farmers sell topsoil to brick kilns to rapidly turn a profit.
The report suggested that agricultural land loss is due to unplanned human settlements, road construction, mill and factory construction, excavation of ponds and tanks, and brick kilns and poultry farms.
Furthermore, topsoil on agricultural lands are degraded during sand extraction by dredgers.
The top layer of soil is losing fertility due to its depletion in organic matter, while farmers apply chemical fertilizers and pesticides for high yields. Indiscriminate felling of trees and water washing down the hills are also causing the topsoil to erode and become infertile.
The DAE report recommends designating zones for procuring soil for brick kilns, and using soil dredged from ponds, rivers, and canals for this purpose.
Additionally, the report suggests allowing brick kilns to be to be set up on two-crop farmlands.
"High and medium-high farmland should not be used for any other purpose," the report adds.
Experts ring alarm bells
Expressing grave concern regarding rapid depletion of topsoil, soil scientists and environmentalists said that non-agricultural use of agricultural land is increasing alarmingly in Bangladesh.
Dr Md Golam Kibria, professor of Soil Science Department at Chittagong University, explained: "A piece of cultivable land should have at least 3% organic matter. Unfortunately, the soil of Bangladesh contains less than 1% organic matter.
"The topsoil, or plough layer, has the highest concentration of organic matter and micro-organisms. Land fertility will be under serious threat if this topsoil depletes further." Kibria added.
Topsoil loss adversely impacts soil aggregate stability.
Good aggregate stability is dependent on organic matter and biological activity in the soil, which helps root development in plants. Poorly-aggregated soil disintegrates easily.
"Topsoil is the most fertile portion of the soil. Plants require 17 essential elements for growth and those elements are found in abundance in the top layer," said Dr Md Al-Amin, professor of Institute of Forestry and Environmental Sciences at Chittagong University.
Farmers are lured into selling the topsoil, which will take 10 to 15 years to regain fertility. A farmer will have to use huge amounts of fertilizer over the years to make up for the loss of topsoil.
"Meanwhile, the sustained growth of cropland will decrease. Eventually the loss would far outweigh the instant monetary gain from selling topsoil," said Prof Amin, adding that sometimes farmers voluntarily sell farmlands adjacent to brick kiln.
This is because the fly-ash produced from a brick kiln spreads up to one kilometre. "The fly-ash deposited on plants reduces the rate of transpiration in a plant. Transpiration is the primary basis by which a plant sustains its life," added Dr Amin.
Dr Md Jahangir Alam, professor of Civil Engineering Department at CUET said that the Housing and Building Research Institute has developed concrete blocks that could substitute clay-rich topsoil bricks.
"We should shift to concrete blocks from burnt clay bricks. The structures made from concrete blocks will be strong, sustainable and cost-effective," said Alam.
Soil scientists also recommend farmers growing legumes along with their main crops, or between harvests.
A leguminous crop refers to those, which have symbiotic nitrogen fixing bacteria called root nodules. These bacteria fix atmosphere nitrogen into soil there by increasing the soil nitrogen content naturally.
They are important for crop rotation in order to avoid soil deterioration.