Soil acidity ails post-mangrove lands

Mashiur Rahaman

back from Chokoria

Level of soil acidity (low pH-level) in almost entire Chokoria sub-district and vast tracts of Sathkhira district has increased dramatically during the last couple of years, turning the regions as 'barren lands', experts have revealed.

Soil Research Development Institute (SRDI), in its soil reaction report, has marked the 21,000 acres of land of southeastern Chokoria and four large pockets of land in the southwest district of Sathkhira as '1a' category soil, saying top soil and subsoil of the two regions has become "extremely acidic."

In the past, both the coastal regions were covered with lush-mangrove forest but human intervention--either in the name of shrimp-cultivation or expansion of agriculture land-has devastated the land, principal scientific officer of Salinity Management and Research Centre (SMRC) Md Anwar Hossain said.

According to soil pH level chart, soil below 'pH-5.0 level' is extremely acidic, making the soil completely out of any use, either for agriculture or fish farming. Standard soil pH level remains between pH 6.6- pH 7.3.

Soil pH level of these marked areas was found to be below that level, Mr Anwar said adding that a vast area surrounding these pockets are a little above the level (between pH 5.1-pH 6.0).

Soil experts say this increasing acidity in the post-mangrove forest areas is the after-effect of deforestation.

As the barren land dries out in summer, the acidic-molecules get concentrated, killing everything above and below the soil surface, experts add.

A recent field study in Chokoria, conducted under a media fellowship by Centre for Science and Environment (CSE) has revealed that crops as well as shrimp production have witnessed a sharp fall in last few years.

"Particularly in the dry season, a thick layer of yellowish chemical surfaces over the shrimp-ghers, causing disease and production loss," a shrimp-gher owner of the once-Chokoria mangrove forest area Abdul Matlub told the FE.

Every year the situation is getting worse, he said, noting: "We've to pump-in additional water to keep the water neutral".

"This is the ultimate fate of all the lands that we have acquired for shrimp or agriculture," soil scientist Anwar Hossain said.

He said that once the soil turned acidic, it is almost impossible to grow crops or farm fish there as acid gets more concentrated.

"This is an eye-opener for all those who advocate expanding agriculture lands or shrimp farming," he told this correspondent.

He suggested the deforested lands should be covered with greenery by planting mangrove forest plants only as an effort to keep the soil from being ruined.

The Chokoria Sundarbans has completely been destroyed in recent years as a result of shrimp farming.

Out of the country's 1,689,831 hactre cultivable coastal area, total 1,056,260 hactre have been affected by saline water, an expanded 35,510 hactre further from 2000 and over 222,810 hactre from 1973, according to a report by SRDI.