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Beginning in 2020 the research of the MultiFruit cluster seeks to optimize food production and the provision of ecosystem services in multifunctional landscapes. Joining agricultural production with the provision of ecosystem services and the preservation of biological diversity, the outcomes of this project aim to provide comprehensive findings to farmers, and the agricultural community as a whole, that are also applicable in the face of climate change. Active apple orchards located in greater Brandenburg, Germany of both organic and conventional management practices have been selected as the sites of research. The present state of organic apple orchards in Germany can best be described as organic “conventionalization”; high yielding orchards with little to no plant diversity, with the major differences being the substitution of synthetic fertilizers, pesticides, herbicides, and fungicides with organic alternatives certified by the Federal Office of Consumer Protection and Food Safety (Bundesamt für Verbraucherschutz und Lebensmittelsicherheit). The project implements an interdisciplinary approach, with researchers of ecology, economics, soil and microbial sciences. The ecological subproject is investigating how local management measures and the surrounding landscapes affect natural pest control by beneficial insects. The soil group are investigating the toxicological and soil health impacts of conventional and organic practices through analysis of both plant and soil material collected from the orchards. Microbial studies seek to provide information on the microorganisms that promote the growth, health, and performance of fruit trees. The economic studies aim to assess the costs and benefits of management measures and resulting pest control services for fruit growers and society as a whole. The overall expected outcome of this cluster is to maximize ecosystem services provided by the orchards while optimizing yield and maintaining soil and orchard health. Here we show the preliminary results of the 2021 field campaign related to the soil group. The processed plant and soil material was analyzed at our laboratory and total elemental concentration of all constituents was determined using Microwave assisted MP-AES for select metals and cations (Zn, Cu, Fe, Al, Mg, Ca, K). These results, in conjunction with measured soil properties (pH, EC, Scheibler carbonate measurement, Total N, Total C) aid in the effort to determine the effects of the various management practices on the soil health and the mobility and translocation of metals and cations within the plant tissues.
Vital, fertile soil is a limited resource and must be considered equal to air and water in its status as a protected good. In Europe, there are around 2.5 million potentially contaminated due to natural and anthropogenic activities. One third of these areas have been identified and 15% of them have already been remediated. An efficient approach for remediation is phytoremediation, a cost-effective and ecosystem-friendly method compared to conventional methods.
We showed that hyperaccumulator plants, which have a high tolerance to the accumulation of potentially toxic elements (PTE), are suitable for phytoremediation methods. Imaging spectroscopy allowed us to monitor and optimize the process of accumulation. Our study was conducted in two steps: First we analysed the potential of multivariate procedures using Partial Least Squares Regression (PLSR) and Random Forest Regression (RFR) to predict highly contaminated areas with an inhomogeneous distribution of PTE concentrations from image data. Therefore, we used contaminated soil samples analysed for heavy metal contents as training data. The fully-trained models assisted to monitor PTE contaminated areas during phytoremediation. In a second step, we investigated hyperaccumulator plants and their spectral fingerprints during PTE uptake to detect the highest possible amount of PTE the plant can tolerate.
Soil samples were measured after different preparation steps (“oven-dried”, “sieved”, “ground”, “Loss on Ignition (LOI)”) with a HySpex VNIR-1600 and HySpex SWIR 320m-e hyperspectral sensor under laboratory conditions. The spectral range of both sensors covers 450 nm to 2500 nm with a spectral sampling interval of 3.7 nm for the VNIR sensor and 6.25 nm for the SWIR sensor.
The resulting spectral library was used for the PLSR and RFR analysis. Considering the optimal coefficient of determination (R2), PLSR showed an improving performance and accuracy with increasing preparation steps: R2_Cr: 0.52–0.78; R2_Cu: 0.36–0.73; R2_Ni: 0.19–0.42 and R2_Zn: 0.41–0.74. In comparison, RFR showed a weaker estimation performance, even when using higher sample preparation levels (R2_Cr:0.36–0.62; R2_Cu: 0.17–0.72; R2_Ni: 0.20–0.35 and R2_Zn: 0.26–0.67). The results indicate that PLSR provides a more robust estimation than the user-friendly RFR method. Additionally, the PTE estimation performance in strong heterogeneous soil samples can be improved by pre-treatment of soil samples in the laboratory.
Second, we cultivated Brassica juncea in a greenhouse and applied the plants with different controlled zinc, nickel and copper concentration levels (low, medium, high). Measurements with a HySpex VNIR-SWIR hyperspectral sensor (408-2500 nm) and a point spectrometer PSR+ from Spectral Evolution (350-2500 nm) were conducted in-situ and in the laboratory. A principal component analysis (PCA) was performed on reflectance spectra to identify and visualize spectral changes with increasing PTE uptake. In addition, different indices were calculated, such as Leaf Area Index (LAI) and Red-Edge Inflection Point (REIP). First results revealed changes at the chlorophyll feature between 500-600 nm and at the REIP position with increasing PTE concentration. Further spectral features and indices will be investigated to check hyperspectral responses of PTE concentration. With reflectance imaging we are already able to detect differences of the PTE accumulation within the hyperaccumulator plants.
Extended dry periods and increasing soil degradation compel the conventional agriculture to shift towards the sustainable practices. Hemp (Cannabis Sativa L.) accounts for crops that require low agricultural inputs and has a high potential to improve soil health hence fertility. The rapid hemp growth, high biomass production and remarkably expanded rooting zone have the vast potential in carbon (C) sequestration and nitrogen (N) fixation. Hemp fibers in the European Union (EU) are commonly used for pulp and paper industry and isolation materials. The study aims to (i) analyze hemp feasibility to grow and contribute to C sequestration under the water scarce conditions in initially nutrient-poor arable sandy soil with high and low canopy densities, and (ii) assess the use of hemp residues like shives and leaves as soil amendments for oat and corn crops in order to increase soil water holding capacity and serve as a long-term nutrient supply. Hemp, oat and corn crops were grown in a greenhouse experiment under LED illumination and wind ventilation for 17 h per day until the harvest. Hemp fibers were obtained through decortication. The biomass of all crops, hemp roots separated into fine and main, soil prior and after the experiment, and soil amendments were investigated for the total C and N content with an ELEMENTAR Vario Max Cube. Also, the elemental analysis for Ca, Mg, K, Zn, Cu, Fe, Al, Na was performed using HNO3 and MP-AES analyses. Total dry root mass for oat and corn crops was measured. Additionally, the soil pH and electrical conductivity (EC) were determined. The results showed that water scarcity had hindered hemp height and biomass production. While under the water limited conditions, the low hemp canopy density had showed slightly advanced growth in comparison to the high canopy density. Furthermore, the results of oat and corn experiment indicated difference between the treatments, where the soil amendment from hemp leaves compared to hemp shives showed enhanced growth in both plant and root biomass