GT3 (Leader UCP-CRP, other partners: ALL)

18 Feb GT3 (Leader UCP-CRP, other partners: ALL)

The specific objectives of GT3 are to assess, within each phytomanagement option,

1. the effect of plant cropping patterns on soil fertility, functional diversity and trace elements (TE) mobility;
2. bioinoculant influence for improving plant performance and soil functionality/diversity; and finally,
3. the effect of biostimulants on plant performance, TE mobility and uptake and soil functionality.

Thirty-five different phytomanagement options were implemented, in which the plant species (perennial and annual species) and plantation patterns (monoculture, polyculture and winter vegetation cover) of each site were selected based on the initial proposal and the data collected at the beginning of the project. The rooting of cuttings of the tree species was started in November 2016 – January 2017 and the rooted young trees were planted in the field in the spring of 2017. The winter crops were established in November 2016 and the annual crops were planted in the spring of 2017. Table GT3.1 summarizes the annual crops (mainly sunflower, tobacco and rapeseed) grown in the different sites. This working group also evaluates the improvement of plant growth and / or the accumulation / exclusion of trace metals in phytoremediation systems. In the first year of the project, 17 different phytomanagement options were established using microbial inocula. Table GT3.2 summarizes the different combinations of plant species, culture patterns and microbial inocula used at the sites.

Finally, the potential use of phytomining techniques is being evaluated. Phytomining proved to be efficient for nickel in the 2000s. However, research has been restricted to the recovery of nickel, while it could potentially be expanded to cover other valuable elements that can accumulate in soils. For example, the extraction and recovery of rare soil elements that have been classified as critical (for example, tungsten (W), rare earth elements (REE)) or as elements of high economic value (gold (Au) or tantalum (Ta)) has rarely been addressed. One of the activities of GT3 is to identify plant species and appropriate sites for gold recovery, and to evaluate the potential use of microorganisms associated with plants to improve the Au phytomining process. During the first year of the project, the initial work involved the prospecting of 9 inactive gold mines in Portugal and determination of metal levels, with special attention to gold, in soils / slag heaps and colonizing plants.

The last activity focuses on evaluating the contribution of organic amendments to improve plant response/establishment and biomass production in areas under phytomanagement. In site S1, new plots were implemented in March 2017 (in triplicate, n = 25, only colonized by some patches of Rumex acetosella and Agrostis sp.) to test the influence of 5 types of organic matter (solid fraction before and after biodigestion of pig manure, compost and compost pellets, and green waste compost) on Cu contamination and soil fertility (total soil Cu around 1000 mg Cu / kg). At the S5a, S5b, S6, S7 and S8 sites, the phytomanagement options which have been implemented are assessing the benefits of organic amendments (composts) elaborated from different residues.

Table-Summary with the phytomanagement schemes evaluated under PhytoSUDOE.

Site history: L, long term; N, new site

Soil amendments: OM, greenwaste compost; DL, dolomitic limestone; OMDL, dolomitic limestone +compost; OM2DL: OMDL plus a second addition of compost; SS, sewage sludge

Table-Summary of bio-inoculants evaluated under PhytoSUDOE.

PGPR, plant growth-promoting rhizobacteria

PGP, Plant growth-promoting

AMF, arbuscular mycorrhizal fungi

The tasks of WG3 during the second year of PhytoSUDOE have focused on the design and establishment of several phytomanagement options at each site, evaluating the benefits of organic amendments (based on organic residues), annual crops, herbaceous and / or woody crops, monoculture planting schemes or co-cultivation incorporating legumes, and bioinoculants based on mycorrhizal and / or bacterial inocula (alone or in combination). The main advance in this WG3 was the establishment and implementation of the numerous experimental plots designed to evaluate all these different aspects. The first harvest of annual crops was completed during the summer of 2017, and at some sites two harvests are available (2016 and 2017).

In the final months of the project, a “Technical guide on strategies to improve the efficiency of phytomanagement: plantation patterns, bioinoculation and biostimulation” was prepared.

In October, 2018, PhytoSUDOE officially ended. The Project deliverables were finalized along January-February, 2019, including the Layman report and the project’s video that were uploaded to the webpage’s news section (blog). Other relevant publications can be accessed also in the web along with the presentations (PDF) of the series of events organized by PhytoSUDOE. This website will be online until 2023.