The main organic input for the elaboration of growing media is peat (Sphagnum spp.), due to its physical and chemical characteristics. However, the mining of this material creates a considerable impact in the local ecosystems from which this is obtained, along with a global impact because of the emission of greenhouse gasses. Thus, sustainable materials that can replace, or reduce the use of peat, while maintaining or improving attributes in the growing media and plant growth, are greatly needed. Therefore, this work aims to evaluate the effects of the use of different proportions of compost and biochar on the biological characteristics of growing media and (Lactuca sativa L.) seedling growth prior to transplanting. Out of the biological variables evaluated, the ?-glucosidase activity showed the greatest results in growing media based on 80% peat and based on 70% peat, 5% compost and 5% biochar. Moreover, growing media based on the combination of compost, biochar and peat maintained most of the Lactuca sativa L. (Oak Leaf variety) seedling traits obtained in the growing media based on only peat. These findings emphasize the need to further investigate further biological conditions for alternative materials to peat, and the need to pay attention to feedstock initial characteristics and processing in order to obtain high quality organic inputs for optimum growing media.

Promover una alianza nacional e internacional con el fin de fortalecer la red de colaboración en el sistema suelo–planta para la generación sustentable e inocua de alimentos, mediante la aplicación de estrategias biotecnológicas y académicas, con foco en el cambio climático y prevención de contaminantes emergentes, como las micotoxinas.

Mining activities have discharged large amounts of wastes or mine tailings to the environment, which represent an important environmental issue. Mine tailings are mainly characterised by poor physicochemical properties that limit the plant establishment and development. The most negative property in these mine wastes is the high content of metals and metalloids [metal(loid)s], which are often highly toxic due to acid pH that increases metal(loid) bioavailability. This negatively affects living organisms and ecological functioning since soil microorganisms are pioneer colonisers that mediate the plant establishment. Also, mine tailings are usually deposited in abandoned locations of large land cover; from where, due to their physical characteristics, they can be transported by air and water, affecting communities and the environment in surrounding areas. There are several industrial strategies focused on the physical and chemical management of mine tailings, but these are highly expensive and occasionally not effective. These strategies have not been suitable techniques to reduce negative impacts of mine tailings on the environment. In this context, biological approaches, such as phytoremediation, have been proposed as more appropriate strategies due to low cost, easy applicability, and promising results. Nevertheless, most of the studies focused on phytoremediation of mine tailings, especially Chilean studies, have been performed in laboratory conditions. Although these studies show promising conclusions, in many cases unsuccessful results are obtained at field conditions, mainly due to laboratory experiments do not consider the dynamic field variability and potential ecological interactions.
Based on the above, the proposed research aims to evaluate the effect of the initial addition of organic-mineral amendments and the bioaugmentation of microbial communities with “core microbiome” from the root-zone of native herbaceous on the growth and development of native plants and microbial communities at copper mine tailings. We hypothesise that the growth and development of native plants in mine tailings will be promoted by the improvement of physicochemical properties of modified mine tailings (incipient technosols) through the addition of organic-mineral amendments, and the bioaugmentation of microbial communities with “core microbiome” involved in plant fitness obtained from copper mine tailings and surrounding soils.
To evaluate the mentioned hypothesis, this study will be executed in three phases: 1) Initial field characterisation: this will be done for mine tailings and soils under sclerophyllous forest; 2) Collection and recruitment of “core microbiome”: this will study the composition, function, and interactions of “core microbiome” obtained from the root-zone of native herbaceous established on mine tailings and soils under sclerophyllous forest, by which a laboratory-scale assay it is needed to produce inoculum of such ecological units (cores); 3) Restoration field experiment: this consists on the field establishment of native herbaceous species by bioaugmentation with “core microbiome” from root-zone mine tailings and root-zone soil on incipient technosols produced by the addition of organic-mineral amendments on mine tailings. These phases are designed to be performed in three years.
This study can provide insights of the promotion of ecological process and natural resilience on microbial communities of mine tailings and surroundings, which can allow the initial plant establishment a development for later possible plant recruitment from the native sclerophyllous forest. This would also evaluate whether mine tailings can be in situ managed instead of been totally removed, which implies high costs and workflow to enterprises. Additionally, this study would represent the first approach of the evaluation of the biological functioning and composition of microbial communities from root-zone mine tailings in Chile, from its current state to the subsequent restoration process.