Effect of phosphogypsum amendment on saline soil and on growth, productivity, and antioxidant enzyme activities of pepper (Capsicum annuum L.)

This research work aimed to study the effects of phosphogypsum (PG) amendment on the physicochemical proprieties of saline soil as well as the biochemical and physiological traits of Capsicum annuum grown under controlled conditions. C. annuum plants were grown on soil amended with different rates of PG varying from 0% to 5%, 10%, and 20%. The effects of PG on C. annuum growth, productivity, nutritional status, antioxidant enzyme activities, heavy metal accumulation, and its potential to use in phytoremediation were also investigated. The results revealed that pH and electrical conductivity of the soil decreased whereas organic matter contents increased in proportion to PG concentration. Both of biomass accumulation and leaf chlorophyll contents were affected by 20% PG amendment in comparison with the 5% and 10% PG and control samples. Beyond 20% of PG, C. annuum plants developed an enzymatic antioxidant defense system in response to salinity and heavy metal stress. In other words, the application of phosphogypsum led to a decrease of potassium (K) concentrations in shoots and sodium (Na) and K in fruits. However, the calcium (Ca), zinc (Zn), cadmium (Cd) and chromium (Cr) accumulation were enhanced both in shoots and fruits. Eventually, Cd and Cr in pepper fruits were found to be above the recommended maximum allowable concentrations. The bioconcentration factor values of Cd in the root of Capsicum annuum were greater than 1, which indicated the Cd accumulation potential by this species. The translocation factor values of Cd and Zn were less than 1, proving that Cd and Zn were stabilized in the root part of the plant.