The role of natural and synthetic zeolites as soil amendments for mitigating the negative impacts of abiotic stresses to improve agricultural resilience

Plants are exposed to different types of biotic and abiotic stresses that reduce growth and yield. The review presents the negative effects posed by salinity, water scarcity and phytotoxic metals to the agriculture sector and underscores the protective role of natural and synthetic zeolites to improve the unfavourable growth environment. Furthermore, based on extensive literature review, zeolites (specifically natural zeolites) possess extraordinary adsorption capacity, highly functional nutrient and water holding and releasing characteristics. The enhanced and selective nutrient retention capacity of zeolites enables lower nutrient loss from soil, thereby minimizing the issue of water pollution through the leaching of excessive nutrients. The adsorption potential of zeolites against Na+, Cl- and various phytotoxic metals in soils improve the growth environment for the plants. Sepcifically, the addition of zeolites to soil facilitates improvements in water availability and better plant growth parameters: chlorophyll content, total protein concentration, and increased activity of antioxidant defense; eventually mitigating the unfavourable effects of environmental stresses such as extreme temperatures, drought or salinity. Natural zeolites, particularly clinoptilolite, were shown to be better in alleviating plant stresses such as salinity in comparison to synthetic zeolites; handling salt load of up to 100 mM of NaCl. Interestingly, zeolites can be used in combination with other substances such as compost, biochar or calcium-based materials to reduce salinity. The greater availability of hydrophilic active sites in zeolites enhances their water sorption strength, restricting the formation of liquid film required for growth of pathogens; delivering effective desiccant-like effects to protect the plants from several pathogens. In general, zeolite applications can be used as buffering agents to improve plant growth and to deliver better biological resilience during different unfavourable growth conditions.