Productivity of Clonal Ilex paraguariensis Genotypes in a Semi-hydroponic System Is Reduced by Shading

Yerba mate (Ilex paraguariensis A. St.-Hil.) is a South American tree cultivated in systems with or without shading at different intensities; however, there is no consensus about shading effect on leaf biomass production. Therefore, we evaluated yerba mate clones under different shading levels over one year to determine the influence of shading and genotype on biomass production. Two yerba mate genotypes (EC22 and EC40), cultivated in a semi-hydroponic system, were subjected to five shading levels (0%, 40%, 51%, 76%, and 82%) in a greenhouse. We determined total fresh biomass (branches and leaves) and fresh biomass of young and mature leaves on six harvests. Biomass production was influenced by harvest season, genotype, and shading levels. Spring and summer harvests provided higher biomass production than the other seasons. EC40 genotype produced higher total fresh and young leaf biomass than EC22. Although we observed differences among genotypes and harvest seasons, shading was the factor that most influenced biomass production. Total fresh biomass productivity was reduced 6.8 times between 0% and 82% shading for the EC40 genotype. Thus, we do not recommend high levels of shade, such as 76% and 82%, in this new yerba mate cultivation system. Study Implications In this study we demonstrated that yerba mate biomass production is influenced by shading levels, harvest seasons, and genotypes. Summer and spring favored biomass production, probably because of high temperatures and solar irradiation. The EC40 genotype had higher biomass production than EC22. Shade at any level reduced yerba mate biomass productivity, and we do not recommend 76% and 82% shade in species cultivation. This study with yerba mate clones clarified issues related to shading effects on biomass production. The semi-hydroponic system proved to be viable for yerba mate cultivation, with high biomass productivity, especially young leaves.