Non-natural soil erosion: Are we shooting ourselves in the foot?

Non-natural factors are causing the soil to deplete fast due to a continuous, indiscriminate and unscientific use of the resource. Experts apprehend this will endanger Bangladesh's food safety and livelihood.

Aggressive farming apart, mindless digging, unplanned habitation, industrialisation, brick kilns and urbanisation have been accelerating the pace of soil erosion.

Because of erosion, coupled with excessive use of insecticides, less use of organic fertilisers, and repeated farming of the same crop, soil health in the country is depleting.

According to research findings, the present rate of loss of cultivable lands is 35 percent more than the formation of new soil.

The eco-system, as a result, will face an adverse effect if the erosion cannot be checked in time. This is because the lower layers of the soil do not contain the same amount of nutritional ingredients as the topsoil does, said experts.

Balanced soil has 45 percent mineral, five percent organic and 25 percent water and air components. Among them, the 5-percent organic component supplies all necessary nutrients for plants.

Research undertaken by the Bangladesh Soil Resource Development Institute in 2017 shows that 61.6 percent of the country's cultivable land is hugely deficient in organic matters. The total area of Bangladesh's arable land is 85.77 lakh hectares, according to the Bangladesh Bureau of Statistics.

Photo: Saikat Bhadra

Research findings by Md Delwar Hossain Mollah, former director of Bangladesh Soil Resource Development Institute, reveal that the presence of organic components in 44.5 percent of cultivable land is less than one percent.

In 17.1 percent of land, the rate is between one percent and 1.74 percent. Considering the soil health, the organic component is 1.74 percent to 3.5 percent in 21.3 decimals of medium quality land, according to the research.

Researchers believe that climate change, intensifying global warming, farming of the same crop for decades, allowing no respite for the land, and imbalanced use of chemical fertilisers have been causing a depletion of the organic components of the soil.

Alongside the farming of new types of crops, the use of chemical fertilisers in the land has been on the rise in a bid to get more yields.

Research shows that where farmers used only two to three types of fertilisers two decades ago, now they go for as many as 17 types of fertilisers in cultivation. In some cases, farmers stagger the use of eight to nine kinds of fertilisers for a single crop.

Experts say soil erosion not only reduces crop yields but also causes various direct and indirect losses.

Bidhan Kumar Bhandar, director at the Soil Resources Development Institute, said dust storms caused by soil loss affect public health and pollute the environment, while continuous soil erosion results in siltation of lowlands and rivers.

Siltation is an obstacle to the free flow of water. As a result, rivers overflow their banks and damage agriculture, he added.

Dr Md Abdul Bari, who is engaged in the Strengthening of Soil Research and Research Facilities project, said, "A balanced use of insecticides, along with preventing soil erosion, is urgently needed in the country. This is because it plays a significant role in increasing crop production.

"We conducted research where we found that production increases by 15 to 20 percent if fertilisers and insecticides are used in a balanced way."

Officials at the Soil Resource Development Institute said farmers can get their soil tested by field level officials of the Department of Agricultural Extension (DAE). If they follow the advice in applying fertilisers, they can maintain the health of the soil.

Applying the right method of farming on hills, shutting down brick kilns and not doing anything else on farmlands can prevent soil erosion, thus saving the health of the soil, according to experts.

Jalaluddin Md Shoaib, secretary of the Soil Science Society, said, "We have research, technology and manpower. Even then, we fail to prevent soil erosion. Prevention of soil erosion will become a major concern if all parties are not sincere in this regard."

Photo: Saikat Bhadra

The global scenario of soil loss

Natural and artificial loss of soil is a matter of concern throughout the world. The main theme of World Soil Day 2019 is "Our Future, Prevention of Soil Erosion". The day will be observed throughout the world on December 5.

In his study conducted on land under maize and wheat cultivation in different states of the United States, scientist Leon Lesis found that yield decreased by six percent when one inch of topsoil was lost from the land.

Hugh Hammond Bennett, another American soil scientist, showed that 60 million tonnes of plant food were washed away every year from the top layer of farmland and grazing fields in the US.

But poor countries face worse conditions due to problems resulting from soil erosion. Soil erosion removes food components 10 times faster than the amount absorbed by crops annually.

In the plains, topsoil is lost through some geological processes such as wind, storm, rainfall, river course, flood and change in the tide of rivers and seas. Soil erosion occurs with the water flowing down from the hills and mountains.

It was in 1968 that the US geologist Sheldon Judson for the first time introduced the world to the reality of a crisis engendered by soil erosion. His research that year revealed that 24,000 million tonnes of earth are being carried by the rivers to the seabed every year.

Photo: Rehman Asad

China's Huang He tops the list of rivers carrying earth the most to the sea, 1,600 million tonnes annually.

Among other rivers, India's Ganges carries 1,455 million tonnes, Brazil's Amazon 363 million tonnes, Egypt's Nile 111 million tonnes and the Mississippi in the US 300 million tonnes of earth to the sea.

Around 23 million tonnes of more soil have been lost to erosion than the silt being deposited on agricultural land around the world, as revealed through various studies, notes the research.

Only a few decades ago, traditional methods were applied in agriculture, which were really helpful in maintaining the environmental balance, according to the research.