Site-specific Nutrient Management for the rice farmers of deltaic region of West Bengal

By Preeti Bharti, Sheetal Sharma, and Ajay Kumar Mishra, IRRI

In India, nearly 95% of the total degraded land is attributed to soil salinity/alkalinity. The Food and Agriculture Organization estimates that over 6% of the world’s land area and approximately 20% of irrigated croplands grapple with salinity issues. Crops show a number of responses to salinity. Salinity affects the germination, growth and reproductive development of the plants as salt accumulates in the root zone.

Salt-affected soils often suffer from poor structure and reduced fertility. By carefully managing nutrients, these soils can gradually improve in structure, fertility, and microbial activity. This includes adding organic matter and enhancing soil structure and nutrient availability.

Site-Specific Nutrient Management (SSNM) provides a balanced approach of nutrient application to farmers, helps them restore the soil fertility and fight soil stresses.

Reasons for coastal soil salinity

Coastal soil salinity primarily results from seawater intrusion, where high oceanic salt levels infiltrate coastal soils. This intrusion arises from factors like rising sea levels, excessive groundwater extraction, and inappropriate irrigation. Climate-induced sea level rise intensifies saltwater ingress into coastal aquifers.

Groundwater is also used for agriculture which results in over-extraction facilitating inland movement of saline water. These combined factors elevate soil salinity thus negatively impacting agricultural productivity.

Impact of soil salinity on crop

High soil salinity profoundly impacts crop production and reduces the yield. Excessive salts hinder germination and seedling establishment, creating osmotic stress that limits water uptake. It also results in ion toxicity, particularly sodium and chloride accumulation which damages plant cells, disrupts nutrient uptake and impends growth. Salinity reduces photosynthesis, diminishing energy production, leading to stunted growth and significant yield decline.

All these affects the crop quality, the nutritional value and market appeal, with economic repercussions for farmers. Effective soil management, including site-specific nutrient management can be helpful for addressing these challenges and ensuring agricultural viability.

SSNM as potential option for offsetting soil salinity

The SSNM approach empowers farmers to adaptively regulate fertilizer application, bridging the gap between crop nutrient requirements and naturally available sources like soil, residues, organics, and irrigation water. Customized nutrient application via SSNM is crucial, especially for salt-affected soils with nutrient imbalances for improving soil health by addressing poor structure and fertility. Incorporating organic matter and enhancing soil structure and nutrient availability contribute to the gradual rehabilitation of salt-affected areas (Buresh and Witt, 2007). Furthermore, the practice of salt leaching, coupled with adequate irrigation and nutrient management, proves effective in reducing soil salinity in coastal regions, creating a more favorable environment for plant growth.

The International Rice Research Institute (IRRI) has used the principles of SSNM and developed a digital tool called Rice Crop Manager (RCM) to provide actionable guidelines to the farmers on crop management. RCM has been developed for rice growers of Philippines, India, Indonesia and Bangladesh. In India, it is available for three States, Bihar, Eastern UP and Odisha.

Dr. Sheetal Sharma, a soil scientist from IRRI, shared that “given the challenges faced by the rice farmers of the deltaic region of West Bengal, a customised advisory from RCM will help in guiding the farmers on managing their rice crops under saline conditions,” . Thus, IRRI will be developing RCM for West Bengal under the CGIAR Initiative on Asian Mega-Deltas in collaboration with the Central Soil Salinity Research Institute.

Nutrient management along with introduction of salt-tolerant varieties will enhance resilience to saline conditions. Regular monitoring and adjustments based on soil health and plant growth will ensure a dynamic and responsive soil reclamation process. Beyond agricultural benefits, site-specific nutrient management brings environmental advantages by minimizing the risk of nutrient runoff into water bodies, crucial for maintaining the balance of terrestrial and marine ecosystems in coastal areas. The economic efficiency of this approach is evident as improved soil health leads to enhanced crop yields with lower input costs over time, making agriculture more sustainable and economically viable.