The plant‐available water associated with the four critical soil suctions vary depending on the different soil textures

Abstract Critical soil suctions of plant‐available water (PAW), including the soil water suction at field capacity ( h FC ), threshold suction ( h threshold ), tipping suction ( h tipping ), and permanent wilting point ( h PWP ). Existing research has confirmed that the hydraulic parameters of different soil textures should not have a single value. Selecting “representative” data to parameterize the deterministic soil critical suction is subjective and biased. Therefore, accurately obtaining the key critical suctions with different textures is crucial for assessing water absorption by crops under drought stress. This study examined soybean responses to progressive drought, focusing on leaf gas exchange and soil water suction. Soybeans were grown until the third pair of true leaves in four soils (heavy sandy, sandy loam, sandy silt, and medium clay) before being subjected to progressive drought. Only h FC of heavy sandy soil meets 100 cm, and h PWP of medium clay is approximately 15,000 cm, while all other soils do not conform to the classic values. The h threshold of medium clay is higher than that of sandy loam and sandy silt. The h tipping for sandy loam, sandy silt, and medium clay are similar, being two to three times greater than that of heavy sandy soil. The lower threshold ( g s = 0) for PAW characterizing gas exchange aligns well with the actual permanent wilting point, while the upper threshold ( g s = 0.9) does not accurately reflect the actual field capacity. The PAW at the four critical soil suctions varies with soil texture. Overall, the assessment of plant stomata response to drought across various soils has clarified the key suctions for different textures.