Nursery preconditioning of Arundo donax L. plantlets determines biomass harvest in the first two years

Abstract

Arundo donax L. has become one of the most promising species for energy production in several subtropical and Mediterranean areas. This species can thrive across a wide range of soil types and is tolerant of many stressful conditions. However, establishment of the crop is critical for the cultivation of A. donax. In this study, we evaluated the effect of nursery preconditioning on survival during transfer to the field and harvests in the first and second year for A. donax. We used early arbuscular mycorrhizae (AM) inoculation, two different substrates, and two pot sizes to generate different nursery conditions that resulted in A. donax plantlets of different sizes and quality. In total, we had 3 treatments. Treatment inoculation: mycorrhizal (AM) plantlets were inoculated with commercial inoculum (AEGIS SYM ®), which contained Rhizophagus intraradices and Funneliformis mosseae, at the time of transplantation, whereas control plantlets were not inoculated. Substrate treatment: half of the plantlets were acclimatized with commercial nutrient-rich agricultural substrate (AS) and half with a mix of agricultural substrate:sand (1:1, v/v) (MIX). Cell size treatment: after 100 days of hardening, 20 plants per treatment were grown in 50 cm3 cells (SC), whereas 20 plants per treatment were transplanted into trays with 300 cm3 cells (BC) in order to generate bigger plants. The results showed a positive effect of the use of AS versus MIX. However, after hardening, AM plantlets grew in MIX substrate presented a greater height, number of leaves, biomass and chlorophyll content than non-mycorrhized (control) plantlets. At the time of transplanting into the field, the plants that remained in small cells were significantly smaller than those that were transplanted into large cells. Additionally, mycorrhizal plants that had been grown in AS had a taller initial height. Plant height at the time of transplantation significantly affected the first- and second-year harvests. Inoculated plants showed higher biomass accumulation than non-inoculated plants after 11 months of growth in an open field. In the second year, only the tray cell size had significant effects on dry biomass harvest. These results demonstrate the potential of the nursery conditions to improve the hardening process of micropopagated plantlets. This could increase the advantages of this propagation method, compared to other methods, and compensate part of its high economic cost.