Effect of soil salinity on cotton cultivation and the potential for introducing Amaranthaceae halophytes in the Yellow River Delta, China

Cotton is a main cash crop in the Yellow River Delta in China. Although cotton is known for its high salt tolerance, cotton yield is severely affected by excessive salt accumulation in soil. A large amount of the Yellow River water is introduced annually to leach surface salts; however, it has limited effects likely due to poor soil physical quality. In this study, we aimed to investigate the impact of soil salinity on cotton growth and the usability of Amaranthaceae halophytes as alternative crops. Cotton and Amaranthaceae plants, including Suaeda salsa, Kochia scoparia, swiss chard, table beets and spinach, were planted in a large field in the Yellow River Delta that had spatial differentiation of soil electrical conductivity (EC). Our analysis on soil revealed that Na+ was the major cause of high EC; however, soil alkalization was not observed in highly salinized areas. Cotton biomass showed a strong negative correlation with field EC. Although all tested Amaranthaceae plants also decreased biomass in high EC areas, this effect was clearly less pronounced in S. salsa. Levels of major (K+, Ca2+ and Mg2+) or minor (Fe2+, Mn2+, Zn2+ and Cu2+) essential elements were not significantly decreased by the increase of field EC in any plant species, except for K+ in S. salsa, suggesting that ion imbalance may not be the primary factor contributing to growth reduction. All Amaranthaceae halophytes absorbed more Na+ but less Ca2+ than cotton, thus planting Amaranthaceae plants may be a better option to prevent the further progression of sail salinization.