Eco-Physiological Response of Rice (Oryza sativa L.) Cultivars to Water Stress and Zeolite Amendment: Implications for Sustainable Production

Abstract

A field experiment was conducted during the 2023 growing season at Al-Jailawiyah, Babylon, Iraq, to assess the effects of natural zeolite soil amendment and three irrigation schedules on growth, grain yield, and health-promoting secondary metabolites in three rice (Oryza sativa L.) cultivars: Nemat, Chakhenoe, and the local Huweizawi. Treatments comprised three zeolite rates (0, 10, and 20 t ha⁻¹) combined with three irrigation regimes (daily, every 3 days, and every 6 days) arranged in a factorial randomized complete block design. Morphological, yield and biochemical parameters — including leaf area, productive tiller number, grain yield, total phenolics, total flavonoids and anthocyanins — were measured at key developmental stages. Significant cultivar × amendment × irrigation interactions were detected. Cultivar Nemat consistently produced the largest leaf area, the highest number of productive tillers, and the greatest grain yield, whereas Chakhenoe accumulated the highest concentrations of phenolic compounds and anthocyanins. Application of zeolite at 20 t ha⁻¹ significantly enhanced yield components and increased levels of secondary metabolites compared with the unamended control. Likewise, the most intensive irrigation (daily) improved growth, yield and biochemical indices relative to less frequent irrigation. The combination Nemat × 20 t ha⁻¹ zeolite under daily irrigation produced the maximum grain yield, while Chakhenoe under daily irrigation (particularly with 20 t ha⁻¹ zeolite) exhibited the richest phytochemical profile. These results indicate that integrating natural zeolite with appropriate irrigation scheduling can improve both productivity and nutritionally relevant phytochemical accumulation in rice, particularly under water-limited conditions. From an environmental and agroecological perspective, zeolite amendment offers a low-cost approach to enhance soil water retention and nutrient stability, thereby contributing to resource-efficient and climate-resilient rice production. Future work should quantify water-use efficiency and long-term soil health effects to refine recommendations for farmers in semi-arid regions.