Influence of rendzina soil amendment on soil water chemistry and biomass productivity at field scale

In the former U mining area of Ronneburg, even after remediation remains of the more than 40 years lasting mining period still affect the environment. Such low to moderate heavy metal and radionuclides (HM/R) contaminated sites are well suited to study phytoremediation approaches combining plants, microbes and soil amendments. One option is lignocellulose production with fast growing trees that at the same time also allows for biodiversity enhancement of degraded habitats, with three stories in height consisting of trees, a harvestable metal accumulation understory, and an erosion protection using gras.

In this context, field scale investigations are applied to areas of moderate HM/R contaminated substrates at the testsites Gessenwiese and Kanigsberg, to investigate phytoremediation strategies (USER-project, PTKA, FKZ 15S9417). Test sites at the basement areas of the heaps were designed to study amongst others (mycorrhiza, streptomyces) the effect of rendzina addition (= calcareous topsoil; 5 Vol%; 20 Vol%) to mining affected soil and its benefits for plant growth. Here, production of woody biomass with fast growing plants in short rotation coppice (SRC) provides a positive effect on biodiversity. Furthermore, quantification of biomass productivity and HM/R-transfer within the soil-plant-water system by using soil and microbial amendments (mycorrhiza, streptomyces) are scopes of this project, and should lead to reduction in leaching of HM/R. Therefore, soil hydrological measurement stations and a lysimeter station are installed to get information about distribution, changes, transfer and output of HM/R in the water phase. Here, addition of calcareous topsoil leads to a reduction of Cd, Co, Ni, Zn and U concentration in soil and seepage water, as well seepage water loads, up to three orders of magnitude between 2015 and 2020.

Additionally, plant growth could be monitored and determined with a high resolution camera system and laserscanning system installed on a microdrone on each test areas over the year period (2016-2020). This confirms the advantage of alder over birch and willow in terms of height growth on soil-amended plots which could be verified by in-situ rating data.