Researchers from the Indian Institute of Technology (IIT) Kharagpur,, in collaboration with the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Hyderabad, have developed and validated Diffuse Reflectance Spectroscopy (DRS) models. This new technology promises faster soil analysis, which could greatly benefit smallholder farming systems.
Years of research by IIT Kharagpur’s Agricultural and Food Engineering (AgFE) Department have demonstrated that DRS is a reliable method for rapid soil assessment. Unlike traditional wet chemistry-based soil testing, which is time-consuming and costly, DRS measures the spectral reflectance of soil samples in non-contact mode and without the need for chemical reagents. The results are then transformed into multiple soil parameters using calibrated spectral algorithms.
Calibrated spectral algorithms are analytical techniques used in the field of spectroscopy to interpret and quantify the data obtained from spectroscopic measurements.
Diffuse Reflectance Spectroscopy (DRS) is a method used to analyze materials like soil by shining light onto them and measuring how the light is scattered and reflected back. The device captures this reflected light across different wavelengths, allowing it to determine various properties of the material, such as its chemical composition and nutrient content.
Study Overview and Results
Rapid soil testing is crucial for addressing soil degradation and improving farm incomes by providing timely and accurate insights into soil health. The study tested Diffuse Reflectance Spectroscopy (DRS) to quickly assess soil chemical properties, nutrient content, and Soil Quality Index (SQI) using samples from 1,112 and 607smallholder farms of Bundelkhand, Uttar Pradesh in 2018 and 2021, respectively. The approach focused on soil pH, electrical conductivity (EC), soil organic carbon (SOC) and key nutrients. Analyses revealed that pH, SOC, and nutrients like Copper (Cu), Iron (Fe), and Sulphur(S) are key for SQI estimation.
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The study claims that DRS can accurately estimate 8 out of 17 soil parameters with up to 80% accuracy. Notably, the soil test crop response (STCR) ratings derived from DRS matched those obtained from traditional wet chemistry methods with an accuracy ranging from 43% to 100%. This high level of accuracy indicates that DRS can effectively support nutrient management strategies, which are crucial for optimizing crop yields.
“This is a great opportunity because most nutrient management strategies are based on STCR ratings, and these ratings may be safely estimated using the DRS approach in a very rapid manner. Over 60% of new samples showed over 70% accuracy, highlighting the potential of applying DRS at various spatial and temporal scales. Our collaboration with ICRISAT has been instrumental in developing these innovative methods for rapid soil health assessment.”
Dr. Jacqueline Hughes, Director General of ICRISAT, added, “ICRISAT has been at the forefront of advancing sensor-based technologies. Our recent work with NIRS (Near-infrared spectroscopy)-based spectroscopy, combined with this pioneering DRS research, underscores our commitment to providing rapid and cost-effective solutions for resource-poor agricultural systems.”
Near-infrared spectroscopy (NIRS) refers to an optical technique that can provide information concerning changes in cerebral oxygen saturation, CBF and volume, cerebral venous oxygen saturation, and cerebral oxygen utilization in the brain.
As the IEEE Standards Association moves towards standardizing soil spectroscopy (P4005 – Standards and protocols for soil spectroscopy), the collaborative efforts of IIT Kharagpur and ICRISAT represent a significant step towards making soil testing through reflectance spectroscopy a practical reality for smallholder farmers.
This advancement heralds a new era of soil health management, promising to enhance the efficiency and accessibility of soil testing across diverse agricultural landscapes.
