This project aims at mapping potential crop yields and the valorization opportunities on marginal soils under various regional conditions in Europe and trying to optimize the biomass production and valorization with biofertilizers or soil additives, like silicon, or management changes.

One project part focuses on inclusion of marginal land for food, feed and energy crops which have the following properties: (1) dry (low water-holding capacity) - agricultural; (2) low organic matter content - agricultural; and (3) contaminated - former industrial and agricultural. We aim to improve the yield and quality of crops cultivated on marginal soils for consumption, fodder and energy purposes by (1) amendment application to increase soil fertility, (2) selenium (Se) supply to increase its content in cereals and fodders, and (3) silicon (Si) fertilization to increase plant resistance to biotic and abiotic stresses. During the first year the field trials were established in Estonia (n=2), Germany (n=1), Poland (n=2), France (n=2) and Lithuania (n=2) with and without inorganic fertilization in combination with either foliar Si or Se fertilization. Field trials with the combination of Si and specially created amendment are carried out in 2021. Various plant species were cultivated according to edaphic conditions: spring barley, timothy grass, and tall fescue. Several field trials are ongoing at two sites with soils contaminated by metal(loid)s and PAH in the Bordeaux vicinity, France. Compost has a long-term beneficial influence for various crops grown on Cu/PAH-contaminated soils. For grassland trials, foliar Se supply increased hay Se content and reduced hay Cd and Zn ones First results are showing that Si addition can contribute toward resilience in poor nutrient conditions.

One goal was to test the potential of Si supply to improve the yield of crop growing on a marginal soil under conditions of climate change; and additionally to estimate the impacts on C sequestration and water supply. We hypothesized that Si would improve crop resistance to drought and pathogens, promote C sequestration, and reduce nitrate leaching. In year 1, Si supply indeed increases crop yield under low nutrient availability, but effect on C sequestration, water supply and nitrate leaching was not evidenced.

The central hypothesis being that processed organic matter (OM) can stabilize yields and improve soils by fostering soil, microbiota and crop interactions, field trials with organic amendments were conducted. In first results, such an amendment led to increase OM content in top soils and water holding capacity, thus contributing toward sustainability. In year 1, the main crop (barley) grew well, and differences between plots were small. Topsoils were sampled across the field plots to identify microbial communities by 16-S sequencing. We aim at unravelling the microbial community structure on seeds, in rhizospheres and field plots and finally follow nutrient use by transcriptome analysis and yield assessment. In a first step, small rhizotrons were used to follow crop growth under controlled conditions and strong effects of the amendment type were recorded "[[figureRep1]]".

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Photo: Colourbox