A recent study in Bangladesh has revealed alarming statistics regarding the decline of Soil Organic Matter (SOM) in the country’s agricultural land. This decline, which affects approximately 80 percent of the agricultural land, has far-reaching consequences for crop production, soil health and food quality.
➡ What is SOM
SOM refers to the decomposed material that is absorbed by plants. It contains various components, including microorganisms and plays a crucial role in soil modification. In Bangladesh, where the climate accelerates the decomposition of organic matter, it is essential for soil fertility, texture, structure and overall quality.
➡ Present Status of SOM in Bangladesh Soil
SOM in Bangladesh Soil (area 8,586,864 ha and percentage of arable lands) under different fertility classes-
- Very Low to Low Fertility Class: This class covers 34.83% of the total area. It represents a significant portion, being the second-largest category in the distribution.
- Medium Fertility Class: This is the largest category, encompassing 59.19% of the total area. It indicates that the majority of the area falls under the ‘Medium’ fertility classification.
- High Fertility Class: A smaller portion of the area, 4.58%, is classified as having ‘High’ fertility. This represents a re
- latively minor segment compared to the ‘Medium’ and ‘Very Low to Low’ classes.
- Very High Fertility Class: The smallest category, covering only 1.40% of the total area, is the ‘Very High’ fertility class. This indicates that such highly fertile areas are quite rare in the total distribution.
➡ The main causes of SOM depletion for soil degradation in Bangladesh
- Intensive cropping practices: Bangladesh has a very high cropping intensity, with many farmers growing two or more crops per year on the same land. These intensive cropping practices can deplete SOM levels over time.
- Monocropping: Many farmers in Bangladesh practice monocropping, which is the cultivation of the same crop year after year on the same land. Monocropping can lead to a decline in SOM levels, as it does not allow for the return of organic matter to the soil from a variety of crop residues.
- Excessive use of chemical fertilizers and pesticides: The use of chemical fertilizers and pesticides has increased significantly in Bangladesh in recent decades. While these inputs can help to increase crop yields, they can also lead to a decline in SOM levels.
- Tillage: Traditional tillage practices in Bangladesh often involve deep ploughing, which can damage soil structure and accelerate SOM decomposition.
- Removal of crop residues: Crop residues are a major source of organic matter for soils. However, many farmers in Bangladesh remove crop residues from their fields to use as fuel or fodder for livestock. This removal of crop residues can contribute to SOM depletion.
- Flooding and erosion: Bangladesh is a flood-prone country and flooding can lead to the loss of SOM through erosion. Additionally, soil erosion can occur in hilly areas of Bangladesh.
➡ The impact of the depletion of SOM in Bangladesh
The impact of soil degradation by the depletion of SOM in Bangladesh is severe and far-reaching.
🅐 Impacts on Soil Health
- Soil Fertility: According to the study, organic matter has fallen below two percent in most of the country’s agricultural lands, where 5 percent organic matter is required for crop land. Organic matter enhances soil fertility by providing essential nutrients and creating a conducive environment for beneficial microorganisms. The decrease in organic matter directly affects soil fertility, leading to reduced crop yields.
- Soil Quality: As per the Bangladesh Soil Resources Development Research Institute, approximately 80 percent of agricultural lands in Bangladesh are deficient in organic matter. This deficiency contributes to soil quality deterioration, making it harder to cultivate and less suitable for crop growth.
- Water Retention: Organic matter helps the soil retain water, crucial in a country like Bangladesh, which often faces water scarcity. Decreased organic matter results in reduced water retention capacity, making crops more vulnerable to drought.
🅑 Impact on Socio-Economy
- Crop yields: SOM plays a vital role in crop production. It improves soil fertility, water retention capacity and structure. When SOM is depleted, crop yields decline. A study by the Soil Resource Development Institute (SRDI) of Bangladesh found that a 1% decrease in SOM content can lead to a 2-3% decrease in crop yields.
- Food security: Bangladesh is a densely populated country with limited agricultural land. Any decline in crop yields can lead to food insecurity for millions of people. A study by the World Bank found that a 10% reduction in crop yields could lead to a 12% increase in poverty and a 15% increase in malnutrition in Bangladesh.
- Poverty levels: Agriculture is the main source of income for millions of Bangladeshis. If soil degradation leads to reduced crop yields, it could lead to increased poverty and rural-urban migration. A study by the International Food Policy Research Institute (IFPRI) found that a 10% reduction in crop yields could lead to a 5% increase in poverty in Bangladesh.
- Environmental quality: SOM plays an important role in carbon sequestration and greenhouse gas mitigation. When SOM is depleted, more carbon is released into the atmosphere, which contributes to climate change. Soil degradation also makes soils more susceptible to erosion and salinization.
🅒 Other impacts
In addition to the above impacts, soil degradation by depletion of SOM can also lead to the following problems in Bangladesh:
- Increased susceptibility to pests and diseases: Depleted soil is less able to support a healthy microbial community, which can lead to an increase in pests and diseases. This is because the microbes that compete with pests and diseases for nutrients and resources are less abundant in degraded soil. Additionally, depleted soil is more likely to be compacted and have poor drainage, which can create favorable conditions for pests and diseases.
- Reduced biodiversity: Soil biodiversity is essential for soil health. A diverse range of soil organisms, including bacteria, fungi and invertebrates, play important roles in nutrient cycling, decomposition and water infiltration. When soil is degraded, the diversity of soil organisms declines. This can lead to a number of problems, including reduced soil fertility, increased susceptibility to pests and diseases and decreased water retention capacity.
- Decreased water quality: Soil plays an important role in filtering and cleaning water. Depleted soil is less able to perform this function, which can lead to decreased water quality. This is because depleted soil is more likely to erode and transport sediment and pollutants into waterways. Additionally, depleted soil is less able to retain water, which can lead to increased runoff and flooding.
- Increased siltation of rivers and canals: Siltation is the accumulation of sediment in rivers and canals. Depleted soil is more likely to erode and transport sediment into waterways. This can lead to increased siltation, which can have a number of negative impacts, including:
- Reduced water quality
- Increased flooding risk
- Damage to infrastructure
- Decreased aquatic biodiversity
- Increased risk of flooding and drought
Depleted soil is less able to retain water. This can lead to increased flooding during periods of heavy rainfall and decreased water availability during periods of drought.
➡ There are a number of ways to correct the depletion of SOM in Bangladesh to protect soil degradation. Some of the most effective methods include:
- Sustainable agricultural practices: This includes reducing tillage, crop rotation, cover cropping and using manure and compost to fertilize the soil. These practices help to improve soil structure, increase microbial activity and reduce SOM decomposition.
- Agroforestry: Agroforestry is a system of land use that combines agriculture with forestry. Agroforestry practices can help to improve SOM levels and soil health by providing a continuous supply of organic matter to the soil.
- Residue management: Crop residues are a major source of organic matter for soils. Farmers should avoid removing crop residues from their fields and instead use them as mulch or incorporate them into the soil. This will help to increase SOM levels and improve soil health.
- Biochar application: Biochar is a charcoal-like substance that is produced by the pyrolysis of organic matter. Biochar can be applied to soils to improve SOM levels, soil fertility and water holding capacity.
- Reducing the use of chemical fertilizers and pesticides: Chemical fertilizers and pesticides can deplete SOM levels over time. Farmers should reduce their reliance on chemical inputs and instead use organic fertilizers and pesticides whenever possible.
- Improved irrigation practices: Over-irrigation can lead to salinization and SOM depletion. Farmers should use efficient irrigation practices such as drip irrigation and sprinkler irrigation to reduce water consumption and improve SOM levels.
In addition to these individual practices, it is also important to adopt a holistic approach to soil management. This means considering the interactions between different soil processes and management practices. For example, reducing tillage can improve soil structure, but it can also lead to increased soil erosion. To mitigate this risk, farmers can plant cover crops or use other soil conservation measures.
By adopting sustainable land management practices and addressing the root causes of SOM depletion, Bangladesh can protect its soils and ensure their long-term health and productivity.
➡ Here are some specific examples of how sustainable agricultural practices are being used to correct SOM depletion in Bangladesh:
A number of farmers in Bangladesh are using cover crops such as dhaincha and mungbean to improve SOM levels and soil health. These cover crops are grown in between main crops and help to reduce soil erosion, increase microbial activity and fix nitrogen in the soil.
Another sustainable agricultural practice that is being used in Bangladesh is crop rotation. Crop rotation involves growing different crops in the same field over time. This helps to prevent soil nutrient depletion and improve SOM levels.
Some farmers in Bangladesh are also using manure and compost to fertilize their crops instead of chemical fertilizers. Manure and compost are rich in organic matter and help to improve SOM levels and soil health.
Agroforestry is another system that is being used to correct SOM depletion in Bangladesh. Agroforestry practices involve growing trees and shrubs alongside crops. This helps to improve SOM levels, increase soil fertility and reduce soil erosion.
One example of an agroforestry practice that is being used in Bangladesh is alley cropping. Alley cropping involves planting rows of trees or shrubs between rows of crops. The trees and shrubs help to improve soil fertility and reduce soil erosion. The leaves and branches of the trees and shrubs can also be used as mulch or incorporated into the soil to improve SOM levels.
By adopting sustainable agricultural practices and agroforestry systems, Bangladesh can protect its soils and ensure their long-term health and productivity.