4.1 Effect of quinoa cultivation on soil physicochemical properties
Quinoa is an apomictic halophyte (Razzaghi et al., 2012) with salt glands or salt capsules, i.e. special epidermal cells that can isolate or exclude excess salt from metabolically active cells (Liphschitz and Waisel, 1982). In the present study, the soil salinity increased in the soil that had been planted with quinoa compared to the unplanted soil (CK), and the salt content of high-density rhizosphere soil (HDR) increased most significantly compared to CK. Nicole Goehring et al (Goehring et al., 2019) estimated quinoa biomass production and soil salinity with different irrigation managements and salinities, and the root zone salinity increased in all treatments, which was consistent with the results of this experiment. Zhang studied Puccinellia ciliata (a salt-tolerant species) through greenhouse experiments and found that salt accumulation also occurred between the roots of salt-tolerant species on saline soils (Zhang et al., 2005). It is suggested that quinoa continually effluxed salt from roots, contributing to increased salinity in the rhizosphere soil, especially in high-density planting (Fig. 1a). Therefore, cultivation of quinoa requires adequate water supply and drainage to remove salt from the soil in the high-density planting area and avoid inhibition of quinoa growth due to salt accumulation.