NIR aquaphotomics reveals water spectral patterns as multidimensional markers of soil-plant interaction under organic fertilization.

Soil serves as the primary medium for root development, water storage, and microbial activity, making it essential for plant growth and development. However, changes in water molecular organization associated with soil-plant interactions under organic fertilization remain poorly understood. In this study, near-infrared (NIR) aquaphotomics was applied to investigate water spectral patterns in soil-plant systems under three fertilization treatments: control, pig manure (PM), and pig manure supplemented with plant-derived liquid fertilizer (PM + LF). Two leafy vegetables, mustard spinach and spinach, were cultivated, and soil and leaf spectra were monitored throughout plant growth using a portable NIR spectrometer (908-1676 nm). The results showed that organic fertilization led to treatment-dependent water spectral patterns in both soil and leaves throughout plant development, reflecting changes in water molecular organization under different fertilization strategies. In soil, prominent spectral changes were observed around 1348, 1366, 1410, 1484, 1503, 1559, and 1589 nm, while leaf spectra showed changes around 1366, 1391, 1410, 1459-1478, and 1509-1577 nm. PM and PM + LF exhibited different water absorbance spectral patterns and aquagram profiles, indicating differences in water molecular organization under the two organic fertilization treatments. These findings highlight the potential of NIR aquaphotomics to use water spectral patterns as multidimensional markers of soil-plant interactions under organic fertilization.