Use of Piptatherum miliaceum to enable the establishment success of Salvia rosmarinus in Technosols developed from pyritic tailings

Abstract

With this study we aimed to assess the effect of the prior development of Piptatherum miliaceum (Pm) in a Technosol on the establishment of Salvia rosmarinus (Sr) as a cash crop. An experimental pot was performed with two biochar (BCh) doses (BCh1 and BCh2) mixed with marble waste and pyritic tailings, with and without Pm. After 12 months of Pm growth, the pots with this species were divided into two sets: Sr alone and Sr + Pm. An agricultural soil (AGR) was used as an external control. The results showed that the growth of Sr led to similar shoot biomass to AGR. Sr + Pm reduced shoot biomass by 50%. Total soil organic and recalcitrant C, and total and recalcitrant N showed the highest values in vegetated pots, with no effect of the BCh rate. The decrease in the soil metals availability was related with increases in soil pH. BCh1Sr + Pm treatment showed a microbial community structure more similar to AGR, related to higher fungal and bacterial abundance, enzyme activities and soluble carbon. Thus, growing Sr + Pm seems a suitable strategy to improve soil properties, including microbial abundance, with low translocation of metals. Although the BCh rate did not affect plant growth or soil physicochemical properties, the lowest rate contributed to the growth of soil microorganisms better. The simultaneous growth of Sr + Pm reduced biomass production, and a source of available nutrients is also recommended. Further studies are needed to test this strategy in the field, and to ensure its suitability and a constant biomass production.

Keywords: Biochar; Facilitation; Metal; Phytostabilisation; Technosol.