Importance of deep water for sugarcane production in both wet and drought years in a rainfed, water-abundant agroecosystem

Authors: Ellsworth, Patrick; White Jr, Paul

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2026
Publication Date: 7/3/2026
Citation: Ellsworth, P.Z., White Jr, P.M. 2026. Importance of deep water for sugarcane production in both wet and drought years in a rainfed, water-abundant agroecosystem. Plant and Soil. https://doi.org/10.1007/s11104-026-08799-8.
DOI: https://doi.org/10.1007/s11104-026-08799-8

Interpretive Summary: High sugarcane yield requires a constant supply of water, and their roots must access sufficient water under both drought or well-watered conditions. The problem is that it is unclear where sugarcane roots are taking up water and if they can access water under all situations. This study was conducted to determine where roots were taking up water during wet and drought years. Using an stable isotope analysis, proportional of water that sugarcane are transpiring coming from the shallow, mid, and deep soil layers was calculated. 2023 had half the typical rainfall, while 2024 had above average rainfall. Deep water uptake (70-200 cm) was the most important water source in both dry and wet years, averaging over half of all water uptake in both years, while shallow soil (0-30cm) was only important in wet years. Sugarcane cultivars did not differ in water source use in either year. Sugarcane yields in the study sites were not reduced by the drought in 2023, showing the ability of deep water to supply enough water. Therefore, access to deep soil by roots is necessary for high sugarcane production in both drought and wet years, so farming practices that improve downward penetration of roots can improve yield.

Technical Abstract: Background and Aims To maintain high productivity, sugarcane roots must provide water to the leaves in both well-watered and water-limited conditions. This study was conducted to determine the depth of water uptake in both wet and dry years. Methods At three sites that differed in clay content, soil samples from 0-200cm soil depth and sugarcane root crown water samples at each site were collected from 4-8 cultivars in May, July, August, and October of 2023 and 2024. Using the isotopic signature of water and the Bayesian mixing model, MixPIAR, proportional water use of the shallow, mid, and deep soil was calculated. Results Plant-available water (PAW) decreased progressively along the soil profile throughout the very dry year 2023 but remained high for most of wet year 2024. Deep water uptake (70-200 cm) was the most important water source in both dry and wet years, averaging 72% in 2023 and 42% in 2024, while shallow soil (0-30cm) contributed only 9% of water uptake in 2023 and 34% in 2024. Sugarcane cultivars did not differ in water source use in either year. Conclusion Access to deep soil is necessary for sugarcane production in both drought and wet years. Sugarcane yields in the study sites were not reduced by the drought in 2023, showing the ability of deep water to meet plant water demands. Thus, cultural practices that improve downward penetration of roots can improve production.