Brazilian Journal of Biosystems Engineering (2022), 16 1091 * Corresponding author E-mail address: costajo@alumni.usp.br (J.O. Costa). https://doi.org/10.18011/bioeng.2022.v16.1091 Received: 04 February 2022 / Accepted: 02 June 2022 / Available online: 17 June 2022 REGULAR ARTICLE Relationships between leaf water potential and soil water potential in grasses subjected to water stress Sergio André Tapparo 1 , Rubens Duarte Coelho 2 , Jéfferson de Oliveira Costa 2 , Sérgio Weine Paulino Chaves 3 , Carlos Alberto Quiloango- Chimarro 2 , Everton dos Santos de Oliveira 1 1 Federal Institute of Mato Grosso do Sul - IFMS, Ponta Porã, MS, Brazil. 2 Department of Biosystems Engineering, Luiz de Queiroz College of Agriculture, University of São Paulo - USP, Piracicaba, SP, Brazil. 3 Departament of Agronomic and Forestry Sciences, Federal Rural University of the Semi-arid Region - UFERSA, Mossoró, RN, Brazil. Regular Section Academic Editor: Fernando Ferrari Putti Statements and Declarations Data availability All data will be shared if requested. Institutional Review Board Statement Not applicable. Conflicts of interest The authors declare no conflict of interest. Funding This research did not receive external funding. Author contribution SAT and RDC: Conceptualization, Experimental data collection, Data custody, Data analysis, Literature review, Writing the manuscript, Manuscript Review. JOC: Data analysis, Literature review, Writing the manuscript, Manuscript Review. SWPC: Experimental data collection, Data analysis, Literature review, Writing the manuscript, Manuscript Review. CAQC and ESO: Literature review, Writing the manuscript, Manuscript Review. Abstract For grasses and other crops in general, soil water potential has been widely studied to determine if there is a deficit or excess of water content in the soil. However, the plant water absorption process is not only modulated by soil water potential but also by the combination of meteorological, soil depth, and crop canopy factors, which could be elucidated through water relations responses. The objective of this work was to compare the water relations of grass species established in different soil depths and subjected to water stress. Santo Agostinho (Stenotaphrum secundatum), Esmeralda (Zoysia japonica), Tanzania (Panicum maximum) and Tifton 85 (Cynodon spp.) were used in this trial. The four species of grasses were tested in four different soil rooting depths: 10, 20, 30 and 40 cm. The grasses were irrigated at soil moisture field capacity level, until the time of imposing the water stress period. Soil depth had a direct influence on leaf water potential and soil water potential. Moreover, correlation coefficients are higher in deeper soil profiles. The strongest correlations between leaf water potential and soil water potential were found in the deeper soil depth treatments. Therefore, for the soil depth treatment of 40 cm, the average R² for the four species was 0.55, the highest being 0.70 in Tanzania grass. It is possible to relate leaf water potential and soil water potential independently of the grass species used or the depth of soil available to the roots, which would allow the creation of new irrigation management strategies. Keywords Water relations; Soil depth; Soil water availability. This artcile is an open access, under a Creative Commons Attribution 4.0 International License. Introduction Irrigation is a key tool for increasing crop productivity, but its non-precise aplication can cause problems with salinization, lixiviation, and waste of water and energy (Wichelns & Qadir, 2015). Research efforts in recent years have concentrated on improving water use efficiency through different techniques (Kang et al., 2017). Knowledge of plant root behavior under water stress is an important aspect for the development of technologies. According to de Melo & van Lier (2021), the water status of plants is modulated by the crop's ability to absorb the water stored in the soil and the combination of meteorological factors interacting with the crop canopy. Therefore, all species of plants, even cultivars, have demonstrated different adaptions to these source-sink limitations (Medrano et al., 2015). The response of plants to soil water potential has been widely studied (Chaves et al., 2022; Costa et al., 2019; Costa et al., 2020a; Hura et al., 2007; Quiloango-Chimarro et al., 2021; Tapparo et al., 2019). However, soil water potential is not necessarily indicative of plant water status in the soil depth explored by the root system (Carlesso, 1995; Coolong et al., 2012). For example, as the soil dries out, plants have more difficulty absorbing water. Therefore, in situations of water stress, the physiological and morphological processes of the plant are subject to adaptations (Chaves et al., 2021; Costa et al., 2018; Jaleel et al., 2009). The chemical, physical and biological characteristics of the soil directly influence the amount of soil water available to plants (Cardoso et al., 2013). Thus, a physical change such as soil compaction, will alter root structure and thus water availability. There is a lack of information on how the plant reacts to water deficits under shallow and deeper soil profiles.