Assessing the potential of red solar-induced chlorophyll fluorescence for drought monitoring in different growth stages of winter wheat

[Display omitted] •SIF687 showed a superior monitoring effect for drought compared to SIF760 and VIs.•SIF687 was the most sensitive to SM during the jointing stage of winter wheat.•Drought and phenological changes reduced the influence of SIF687 on PAR.•Compared to LAI, SIF687 was more affected by Chl under drought conditions. Compared to traditional vegetation indices (VIs), Sun-induced chlorophyll fluorescence (SIF) has the advantage of rapid response to drought and early drought detection. However, the response of red SIF (SIF687) to drought at different growth stages of winter wheat remains unclear. Therefore, this study focuses on winter wheat and sets up three irrigation treatments with different drought intensities. Spectral data collected by an automated spectral observation system are used to retrieve SIF687, far-red SIF (SIF760), the Normalized Difference Vegetation Index (NDVI), the Near-Infrared Reflectance Index (NIRv), as well as meteorological data, soil moisture (SM), and vegetation growth parameters. The goal is to investigate the response of SIF687 to drought at different growth stages of winter wheat. The results indicated that SIF687 showed a positive response to drought, compared to the condition without drought, SIF687’ change rate (31.19% and 47.38%) exhibited a superior monitoring effect for moderate and severe drought than that of SIF760 (13.10% and 10.63%) and VIs (−4.84% and −4.02%), with the jointing stage showing the highest sensitivity to changes in SM. Under different scenarios, the effects of photosynthetically active radiation (PAR), vegetation physiology and canopy structure on SIF687 were different. With the increase of drought intensity and the development of growing season, the impact of PAR on SIF687 gradually decreased. The response of SIF687 to drought was more affected by physiological changes (chlorophyll content, Chl) than by vegetation structure changes (leaf area index, LAI). In summary, SIF687 possesses the potential for early drought monitoring in winter wheat. It can provide timely responses to water stress at different growth stages, thus contributing to the mitigation of agricultural drought risks.