The pressure to produce more crops from the same amount of land has caused two-fifths of the total arable land area of Bangladesh to become deficient in organic elements and other nutrients, experts have warned.
According to the Soil Resources Development Institute (SRDI), about 42% of the total arable land areas – which is around 43.4 lakh hectares – currently lacks the standard proportion of organic matter in the topsoil.
“The presence of organic nutrients determines the soil health,” Md Delowar Hossain Molla, director of SRDI, told the Dhaka Tribune.
“We roughly consider it healthy for the soil to have 5% organic matters, but the soil of around half of the country’s arable land areas lacks the standard level.”
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The SRDI director cited the excessive use of chemical fertilizers in farming as one of the major causes of the depletion of organic matters.
Records show that the use of such fertilizers in Bangladesh increased by 66% from 1999 to 2008, in tandem with a 340% rise in government subsidies on them over the same period.
“In addition to excessive use of chemical fertilizers, the rising trend of multiple cropping and a failure to maintain sustainable crop-rotation methods have eventually led to over-extraction of nutrients from the soil,” Delowar Hossain Molla said.
In recent years, the successive cropping of rice in a year has gradually replaced the traditional practice of rice cultivation in rotation with leguminous crops.
However, the cultivation of leguminous crops in the gaps between rice harvests minimises the intake of nitrogen by rice plants. Nitrogen rests in soil in both organic and inorganic forms, and over 90% of the soil nitrogen is associated with soil organic matter.
“Soil health condition in Bangladesh has drastically deteriorated in the last couple of decades, in inverse relation with the target of producing more crops from a small amount of land,” the former director general of the Department of Agricultural Extension, Hamidur Rahman, said.
“Now the farmers produce even more crops in a single piece of land annually, which gives more yield and money, but eventually damages the soil health.
“There is no denying the need of using chemical fertilizers and adopting multiple cropping to meet the growing demand of food, but the farmers should at the same time be encouraged to use more organic fertilizer along with the chemical ones to recover the soil health,” he suggested.
The SRDI records also show that around 3.7 million hectares of land is facing phosphorus deficiency, while 2.72 million hectares lack potassium, 3.31 million hectares lack sulphur, 275,000 hectares lack zinc, 2.49 million hectares lack boron, and 300,000 hectares lacking both calcium and magnesium.
Hamidur Rahman said: “The farmers should cultivate different types of crops in the land alternatively. Because different crops extract different types of soil nutrients.”