Limited Irrigation Effects on Biomass, Growth Characteristics, Nutritive Value and Hyperspectral Wavelength in Alfalfa

Soil moisture affects alfalfa biomass, nutritive value and physiological processes. Implementing precision agriculture for moisture management during alfalfa cultivation can help sustain high-quality forage production. This study aimed to assess limited irrigation effects on biomass, growth characteristics, nutritive value and hyperspectral wavelength in alfalfa (Medicago sativa L.).

The experiment was conducted in a greenhouse at Kansas State University from May to November 2024. Irrigation was applied based on field capacity (FC) at four levels namely 55% (FC55), 70% (FC70), 85% (FC85) and 100% (FC100).

The findings indicated that above- and below-ground biomass and growth characteristics, including growth stage, leaf area index, number of nodules, crown size and taproot diameter as well as normalized difference vegetation index (NDVI) improved with increasing FC. FC85 appeared to be the optimal growth condition related to roots and nodules. The leaf to stem ratio was highest in FC55, which showed the same trend as nutritive values, including crude protein (CP), acid detergent fiber (ADF) and relative feed value (RFV). The hyperspectral reflectance was high in FC55, indicating drought stress. The optimal field capacity for balanced above- and below-ground growth in alfalfa appeared to be 85% while showing signs of water stress in FC55.