Potassium Humate and Plant Growth-Promoting Microbes Jointly Mitigate Water Deficit Stress in Soybean Cultivated in Salt-Affected Soil

Khadiga Alharbi; Emadeldeen Rashwan; Emad Hafez; Alaa El-Dein Omara; Hossam Hussein Mohamed; Tarek Alshaal

doi:10.3390/plants11223016

Potassium Humate and Plant Growth-Promoting Microbes Jointly Mitigate Water Deficit Stress in Soybean Cultivated in Salt-Affected Soil

Plants (Basel). 2022 Nov 8;11(22):3016. doi: 10.3390/plants11223016.

Authors

Khadiga Alharbi¹, Emadeldeen Rashwan², Emad Hafez³, Alaa El-Dein Omara⁴, Hossam Hussein Mohamed⁵, Tarek Alshaal^{6

7}

Affiliations

¹ Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia.
² Agronomy Department, Faculty of Agriculture, Tanta University, Tanta 31527, Egypt.
³ Department of Agronomy, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt.
⁴ Agricultural Research Center, Microbiology, Soils, Water Environment Research Institute, Giza 12112, Egypt.
⁵ Department of Agronomy, Faculty of Agriculture, Ain Shams University, Cairo 13625, Egypt.
⁶ Soil and Water Department, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt.
⁷ Department of Applied Plant Biology, Institute of Crop Sciences, University of Debrecen, Böszörményi Street 138, 4032 Debrecen, Hungary.

Abstract

Lack of high-quality irrigation water and soil salinity are two main environmental factors that affect plant development. When both stressors are combined, the soil becomes sterile and constrains plant productivity. Consequently, two field trials were designed to assess whether plant growth-promoting microbes (PGPMs; Bradyrhizobium japonicum (USDA 110) and Trichoderma harzianum) and potassium humate (K-humate) can stimulate soybean growth, productivity, and seed quality under two different watering regimes as follows: (i) well-watered (WW), where plants were irrigated at 12-day intervals (recommended), and (ii) water stress (WS), where plants were irrigated at the 18-day intervals in salt-affected soil during 2020 and 2021 seasons. Results revealed that coupled application of PGPMs and K-humate resulted in a substantial improvement in K⁺ levels in the leaves compared to Na⁺ levels, which has a direct positive impact on an enhancement in the antioxidants defense system (CAT, POX, SOD), which caused the decline of the oxidative stress indicators (H₂O₂, MDA, and EL%) as well as proline content under water stress in salt-affected soil. Hence, a significant increase in root length, nodule weight, soybean relative water content (RWC), stomatal conductance, photosynthetic pigments, net photosynthetic rate, soluble protein, seed carbohydrate content as well as the number of pods plant^-1 and seed yield was reported. In conclusion, the combined application of PGPMs and K-humate might be recommended to maximize the soybean growth and productivity under harsh growth conditions (e.g., water stress and soil salinity).

Keywords: Glycine max; PGPMs; antioxidant enzymes; oxidative stress; plant growth stimulants; soil salinity; watering regimes.

Grants and funding

This research was funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2022R188), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.