Potential ways of recovering sulfur deficiency in soil

At least 17 basic elements are required for crop production. Of these, 9 major nutrients are absorbed by plants in large quantities. Of which three main elements namely carbon, hydrogen and oxygen are obtained by plants from air and water. The three primary nutrients such as nitrogen, phosphorus and potassium are available from the soil. The remaining three major nutrients such as sulphur, calcium and magnesium are obtained from the soil. Apart from this there are 8 other nutrients such as iron, molybdenum, boron, copper, aluminium, manganese, zinc and chlorine which are required in the soil. In the absence of any one of these nutrients, the growth and development of plants cannot take place properly. As a result, the crop yield is severely reduced.

Since the introduction of modern agricultural systems, the soil has been deficient in basic elements. Nitrogen deficiency occurred in the soil of Bangladesh in 1951. Then, from 1957, phosphorus was added to the deficiency list along with nitrogen. Potassium was added to this list around 1960. Since 1980, sulfur has also been added to the deficit list. Since 1982, zinc has been added to the deficiency list. Since 1995 there has been a shortage of boron. The list of deficits has grown longer since 2000. Agricultural production in Bangladesh is now deficient in eight essential nutrients such as nitrogen, phosphorus, potassium, sulphur, zinc, boron, magnesium and molybdenum. Scientists fear that if agricultural production based on artificial fertilizers is conducted as it is now, in the near future at least 17 basic nutrients and fertilizers will have to be used to produce crops in this country.

Sulfur is one of the 17 essential nutrients for plants. It is essential for the growth and development of almost all crops. Like any essential nutrient, sulfur (S) has some fundamental functions for plant growth and development. Sulfur mainly plays a role in the formation of chlorophyll, which makes plant starches, sugars, oils, fats, vitamins and other compounds through photosynthesis. Sulfur is a component of three S-containing amino acids (cystin, cysteine, and methionine), which are the building blocks of proteins. These amino acids are present in about 90% of plant S. This is why adequate sulfur is crucial for oil synthesis in plant seeds. Sulfur activates enzymes that help in biochemical reactions in plants. Increases crop yield and improves product quality. Sulfur determines the quality and market value of a farmer's produce. Sulfur promotes protein synthesis in plant seeds, determines the percentage of oil in seeds, improves the quality of cereals for milling and baking, and is directly related to the special metabolism of plants and the structural characteristics of protoplasm. Moreover, sulfur helps in the growth and development of plants. If there is a deficiency of this element, the crop as time to maturity increases, value also decreases.
A study by the Soil Resources Development Institute shows that, in 2000, the amount of land with fertility deficiency in the country was 11.1 million hectares. About one lakh more in the next 20 years hectares of land have been added to the list.By 2020, the amount of land in the country with fertility or nutrient deficiency stands1 crore 11 lakh hectares, which is about 75 percent of the country's total land.In total 20 years from 2001 to 2020, sulfur deficiency has increased in 11 lakh 10 thousand hectares of land across the country. About 76 lakh 40 thousand hectares or 51.8 percent of land is deficient in sulphur.

 Sulfur deficiency is occurring in the soil of Bangladesh day by day. Sulfur content (very low to low) of loam to clayey soil in wetland paddy field was 34.45% in 2010 and increased to 46.41% in 2020 and moderate sulfur content was 18.65% in 2010 and it increased to 20.41% in 2020. Reaching 92%. Optimum soil sulfur content increased from 11.39% (10,93,299 ha) to 15.21% (13,05,808 ha) and between 2010-2020 soil sulfur content (high to very high) was 35.51 % decreases to 17.43 %.

Another study was conducted during the financial year 2022-23 from the Soil Resource Development Institute, Regional Laboratory, Faridpur when this is the picture of nutrient content across the country. Incorporation of data on pH, Phosphorus, Potassium, Sulfur for determination of soil fertility or nutrient quality of Faridpur region.

About 743 soil samples were collected from different points of Faridpur district. Analysis of these samples shows that 28 percent of land has very low and 33.51 percent of land has low sulfur deficiency and 19.11 percent of land has moderate sulfur deficiency. Altogether 80.61 percent of land is sulfur deficient. Only 19.39 percent of land is not sulfur deficient.

What happens when the soil is sulfur deficient: One report says that when the sulfur content in the soil decreases, the productivity of the soil decreases. Productivity can be reduced by 50-75% at soil sulfur content of 9.0 ppm or below and 25-50% at soil sulfur content of 9.1-18.0 ppm. Soil sulfur between 18.0-23.5 ppm can reduce productivity by 10-25%. According to experts, if a very important soil element like sulfur is reduced in this way, it can have a fatal negative effect on the yield.

All over the country the sulfur content of wetland rice crops has been significantly reduced from loam to clay soils. This may be due to increased cropping intensity and insufficient use of sulphur-rich fertilizers. According to one statistic, 360,000 metric tons and 115,000 metric tons of gypsum and sulfur containing zinc fertilizers were used in agriculture in 2019-20, respectively. Which means that the average amount of sulfur fertilizer used in the soil of Bangladesh was 55.32 kg per hectare.

What to do: To remedy soil nutrient deficiency, it is possible to prevent soil nutrient loss by checking soil quality and applying moderate amounts of balanced fertilizers. To control the loss of soil organic matter, organic matter should be added to the soil by applying organic fertilizers. Plant or crop residues should be mixed into the soil. Besides, keeping animals in the same place along with crops will make it possible to eliminate the deficiency of organic matter through their dung.

Finally, soil health is closely related to human health. Sustainable soil management is essential to ensure food security. Bangladesh's agriculture is now in the process of transitioning from subsistence agriculture to commercial agriculture. Conserving soil biodiversity and maintaining its fertility is vital for the country's future agricultural production. Therefore, it is the demand of time for everyone to take initiatives in this regard.

The writer is Principal Scientific Officer, Soil Resource Development Institute, Ministry of Agriculture, Regional Laboratory, Faridpur