Effect of irrigation regimes on spectral reflectance of soybean cultivars

This study investigates the effects of various irrigation regimes on the spectral reflectance and growth performance of four soybean cultivars (Glycine max L.) during the summer season of 2022 at Mahatma Phule Krishi Vidyapeeth, Rahuri, Maharashtra, India. The experiment was designed using a split-plot layout, featuring four irrigation levels (1.0, 0.75, 0.50 IW/CPE ratios, and irrigation every 15 days) and four soybean cultivars: Phule Sangam, Phule Kimaya, Phule Durva, and JS-9305. Spectral reflectance measurements were collected at five intervals, focusing on blue, green, red, and near-infrared wavelengths. The study revealed that increased water stress led to higher spectral reflectance values in the blue, green, and red wavebands, while near-infrared reflectance decreased. Normalized Difference Vegetation Index (NDVI) values were significantly higher for the Phule Kimaya cultivar, especially at the 1.0 IW/CPE irrigation level, indicating greater biomass and photosynthetic activity. The grain yield results also favored Phule Sangam under 1.0 IW/CPE irrigation, with the lowest yield observed in JS-9305 under the 15-day interval irrigation regime. The study highlights the utility of NDVI and spectral reflectance as indicators for assessing water stress in soybean crops and optimizing irrigation practices.