Taha A. Al-Issa 1, Sajeda A. Al-Twaiq 1, Maher J. Tadros 1,2, Laith M. Alomari 3,4, Husam J. Omari 1*, Laith M. Rousan 1 and Yaser N. Aldwairi 1
1Department of Plant Production, Jordan University of Science and Technology, Irbid 3030, Jordan; 2Department of Natural Resources and Environment, Jordan University of Science and Technology, Irbid 3030, Jordan; 3Department of Horticulture, Iowa State University, Ames, IA 50011, USA; 4Department of Agriculture Sciences of Al-Shoubak University College, Al-Balqa Applied University, Al-Salt 19117, Jordan
*Corresponding author: omhossam13@agr.just.edu.jo
The safe reuse of wastewater in forage production is constrained by the risk of heavy metal accumulation and nutrient imbalance in plant tissues and growth media. Although natural zeolite, mainly composed of clinoptilolite, has been reported to mitigate such risks, the optimal soil–zeolite mixing ratio for alfalfa performance under contrasting irrigation water qualities remains poorly defined. Therefore, this study aimed to evaluate the potential role of natural zeolite in enhancing alfalfa growth and mineral composition while reducing heavy metal uptake under irrigation with treated and raw wastewater. A greenhouse experiment was conducted during the summer of 2024 at Jordan University of Science and Technology (JUST). The study followed a randomized complete block design with 15 treatments, including five soil–zeolite mixtures and three irrigation types: distilled water (DW), treated wastewater (TWW), and raw wastewater (WW). The results showed that alfalfa growth, mineral composition, and heavy metal accumulation were significantly influenced by the interaction between growth media and irrigation type (P<0.05). The 25% soil: 75% zeolite (25% S: 75% Z) treatment under WW irrigation recorded the highest plant fresh and dry biomass and the highest nitrogen and phosphorus contents, probably due to improved nutrient retention and root-zone buffering associated with clinoptilolite’s high cation exchange capacity. Magnesium and sodium contents increased with increasing zeolite proportion, with the highest values recorded in plants grown in pure zeolite (100% Z) under WW irrigation. Nickel (Ni) and lead (Pb) were detected only under WW irrigation and were absent under DW and TWW. Increasing zeolite proportion reduced Ni and Pb concentrations in both plant tissues and growth media, with greater reductions at higher zeolite proportions. Overall, the 25% S: 75% Z mixture provided the most favorable agronomic balance, as it enhanced alfalfa biomass production and nutrient status while substantially reducing heavy metal accumulation compared with pure soil. These findings emphasize the importance of natural zeolite as a sustainable amendment for safer wastewater reuse in agriculture, forage production, and environmental protection.