Sodic soils restrict the movement of water and air in the soil, negatively affecting plant growth. Sodic soils are storehouses of various problems like shallow wetting zones, temporary waterlogging, and diminishing water storage in root zones.
Indo-Gangetic plains of India have a large extent of the salt-affected area. As a result, excessive salt in the soil affects wheat and rice farming in Indo-Gangetic plains. To tackle this problem India’s farmers need a more affordable way of addressing excessive salt in the soil.
As per a study published last month, by Agroecology and Sustainable Food System, India has 2.8 million hectares of land, mostly in the Indo-Gangetic alluvial plains, that are ‘sodic’ and that can be recovered by treating it for excess sodium. In other words, treatment with gypsum and organic manure followed by sowing with salt-tolerant crop varieties will improve soil cost-effectively.
Present Soil Remediation of Sodic Soils
Current soil remediation of sodic soils in India includes the addition of 50% gypsum followed by cultivating traditional varieties of rice and wheat. But, this is unaffordable for smallholders who farm on the upper Indo-Gangetic plains which extend over 150,000 square kilometers.
Each hectare of sodic soil requires 12 to 16 tons of gypsum for remediation which, at US$60 per ton, is beyond smallholder and marginal farmers. According to research, 60% of the total cost of reclamation goes towards gypsum. This costs a lot and also this mineral is becoming scarce because of demand for nonagricultural uses.
Affordable Soil Remediation of Sodic Soils
According to a new study conducted in Hardoi district on Indo-Gangetic plains of Uttar Pradesh, treatment using 25% gypsum, 10% magnesium, and pressmud (organic fertilizer made from sugar cane residue), followed by sowing with salt-resistant varieties of wheat and rice doubled the crop productivity.
India, a major sugarcane grower, produces about 12 million tons of pressmud annually. Pressmud contains nutrients, organic matter, and a high amount of calcium sulfate, which supplies calcium directly to the soil to replace excess sodium.
Conclusion
Out of 584 Indian districts, 194 have either saline or sodic soils and a large proportion of affected lands are cultivated by smallholders. Alternate wet and dry seasons and the general topography exacerbate problems caused by sodicity and salinity. During the wet season, salts accumulate in low-lying areas, and in the dry season, they concentrate due to the high evaporation of water. As a result, the number of sodium ions increases in the soil.
As per the report published, the benefits of the Hardoi study can be extended immediately to the salt-affected areas of the Ganges mega deltas in India and Bangladesh.