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The global demand for energy security and the mitigation of climate change are the main drivers pushing the production of crops for energy purposes (energy crops). However, the cultivation of these plants can cause land use conflicts since agricultural soil is mostly used for food crop production. A sustainable alternative to the conventional cultivation of food-based energy-crops is the cultivation of non-food energy crops on marginal lands. To further increase the sustainability of energy crop cultivation systems the dependency on synthetic fertilizers needs to be reduced via closed nutrient loops in the production chain for bioenergy. In the present study Sida hermaphrodita was used to evaluate its potential as an energy crop to be grown on a marginal sandy soil in combination with a fertilization using digestate from biogas production. With this dose-response experiment we identified an optimum digestate dose of 40t ha -1 corresponding to the highest biomass production, which was compared to an equivalent dose of mineral NPK-fertilizer. Further, 240t ha -1 had lethal effects on Sida hermaphrodita . A digestate dose of 5t ha -1 showed no fertilization effect. Digestate fertilization built up a pool of soil organic matter (SOM). The slow release of nitrogen from this organic pool could serve as long term fertilization and help to limit the high risk of leaching on marginal soils. Accordingly we see a potential of biogas digestate as a sustainable alternative to mineral fertilizers for the cultivation of the energy crop Sida hermaphrodita on marginal soils. [ABSTRACT FROM AUTHOR]

The fate of the 14C-labeled herbicides ethidimuron (ETD), methabenzthiazuron (MBT), and the fungicide anilazine (ANI) in soils was evaluated after long-term aging (9–17 years) in field based lysimeters subject to crop rotation. Analysis of residual 14C activity in the soils revealed 19% (ETD soil; 0–10 cm depth), 35% (MBT soil; 0–30), and 43% (ANI soil; 0–30) of the total initially applied. Accelerated solvent extraction yielded 90% (ETD soil), 26% (MBT soil), and 41% (ANI soil) of residual pesticide 14C activity in the samples. LC-MS/MS analysis revealed the parent compounds ETD and MBT, accounting for 3% and 2% of applied active ingredient in the soil layer, as well as dihydroxy-anilazine as the primary ANI metabolite. The results for ETD and MBT were matching with values obtained from samples of a 12 year old field plot experiment. The data demonstrate the long-term persistence of these pesticides in soils based on outdoor trials. [Copyright &y& Elsevier]

Twenty-two years after the last application of ring-14C-labeled atrazine at customary rate (1.7kg ha−1) on an agriculturally used outdoor lysimeter, atrazine is still detectable by means of accelerated solvent extraction and LC-MS/MS analysis. Extractions of the 0–10cm soil layer yielded 60% of the residual 14C-activity. The extracts contained atrazine (1.0μg kg−1) and 2-hydroxy-atrazine (42.5μg kg−1). Extractions of the material of the lowest layer 55–60cm consisting of fine gravel yielded 93% of residual 14C-activity, of which 3.4μg kg−1 was detected as atrazine and 17.7μg kg−1 was 2-hydroxy-atrazine. The detection of atrazine in the lowest layer was of almost four times higher mass than in the upper soil layer. These findings highlight the fact that atrazine is unexpectedly persistent in soil. The overall persistence of atrazine in the environment might represent a potential risk for successive groundwater contamination by leaching even after 22 years of environmental exposure. [Copyright &y& Elsevier]

Algae effectively accumulate phosphorus (P) from the environment, qualifying them as a promising novel P fertilizer. We hypothesized that P in algae can be rapidly transformed in soil and mobilized for plant growth. To determine the fate of algal fertilizer in soil and to trace its efficiency for plant uptake, we labeled the algae Chlorella vulgaris with the radioisotope 33P. To optimize the labeling we studied P-uptake dynamics in detail using a pre-starved culture and additionally monitored polyphosphate (Poly-P) and organic carbon (C) reserve pools by Raman microscopy. Using an optimized labeling procedure, the concentrations and distribution of both algae-derived 33P and mineral fertilizer 33P (control) were characterized in incubation and rhizotron experiments. Soil incubation was performed with four major reference groups (Andosol, Alisol, Cambisol, and Vertisol). To assess 33P plant uptake we grew wheat in rhizotrons on Cambisol. Soil analyses at different incubation times demonstrated sequential 33P fractionation, while plant uptake of algae-derived 33P was followed using sequential autoradiographic imaging. We found that the algae increased labile P pools comprising Resin- and NaHCO 3 -extractable P in soils during the first 2 weeks of incubation, similar to the effects of NPK fertilizer. The soils with elevated concentrations of Fe- and Al-oxides (Andosol and Alisol) immediately bound 55 to 80% of the applied fertilizer 33P into the moderately available NaOH-P fraction, whereas the soils with lower concentrations of Fe/Al-oxides (Cambisol, Vertisol) stored 35–71% of the algal-P in the labile fraction. The rhizotron experiments visually supported the release and plant-uptake of algal 33P, thus verifying the suitability of algal-fertilizer for plant growth. • Incorporation of 33P label by algae was fast and ranged between 66 and 99%. • Incorporation of P was largely in the form of Poly-P granules. • Algae increased labile P pools in soils comparable to mineral P-fertilizer. • P from algae was quickly mineralized and taken up by wheat roots. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a non-renewable resource, a major plant nutrient that is essential for modern agriculture. Currently, global food and feed production depends on P extracted from finite phosphate rock reserves mainly confined to a small number of countries. P limitation and its potential socio-economic impact may well exceed the potential effects of fossil fuel scarcity. The efficiency of P usage today barely reaches 20%, with the remaining 80% ending up in wastewater or in surface waters as runoff from fields. When recovered from wastewater, either chemically or biologically, P is often present in a form that does not meet specifications for agricultural use. As an alternative, the potential of microalgae to accumulate large quantities of P can be a way to direct this resource back to crop plants. Algae can acquire and store P through luxury uptake, and the P enriched algal biomass can be used as bio-fertilizer. Technology of large-scale algae cultivation has made tremendous progress in the last decades, stimulated by perspectives of obtaining third generation biofuels without requiring arable land or fresh water. These new cultivation technologies can be used for solar-driven recycling of P and other nutrients from wastewater into algae-based bio-fertilizers. In this paper, we review the specifics of P uptake from nutrient-rich waste streams, paying special attention to luxury uptake by microalgal cells and the potential application of P-enriched algal biomass to fertilize crop soils. [ABSTRACT FROM AUTHOR]

Perennial non-food energy crops are currently discussed as a more sustainable alternative to conventional energy crops like maize. As they can be cultivated on marginal soils, they reduce the risk of land use and food vs. fuel conflicts. In this study, we evaluated the perennial energy crop Sida hermaphrodita for its potential to be cultivated on marginal substrate and conventional agricultural soils over a three-year field and mesocosm experiment at agricultural conditions. Furthermore, we aimed for a closed nutrient loop by fertilizing plants with biogas digestate and using the carbon fraction of the digestate as soil amendment to ameliorate the overall soil fertility. As controls, plants were either untreated or fertilized with an equivalent amount of mineral NPK fertilizer. We found S. hermaphrodita to give highest DM yields of up to 28 t ha −1 under favorable soil conditions when fertilized with mineral NPK. However, on marginal substrate digestate fertilization resulted in a clear biomass yield advantage over NPK fertilization. An increased soil carbon content, water holding capacity and basal soil respiration indicated improved soil fertility in the marginal substrate. These results demonstrate the great potential of S. hermaphrodita to be cultivated on marginal soil in combination with organic fertilization via biogas digestate. [ABSTRACT FROM AUTHOR]

Growing energy crops in marginal, nutrient-deficient soils is a more sustainable alternative to conventional cultivation. The use of energy-intensive synthetic fertilizers needs to be reduced, preferably via closed nutrient loops in the biomass production cycle. In the present study based on the first growing season of a mesocosm experiment using large bins outdoors, we evaluated the potential of the energy plant Sida hermaphrodita to grow in a marginal sandy soil. We applied different fertilization treatments using either digestate from biogas production or a commercial mineral NPK-fertilizer. To further increase independence from synthetically produced N-fertilizers, the legume plant Medicago sativa was intercropped to introduce atmospherically fixed nitrogen and potentially facilitate the production of additional S . hermaphrodita biomass. We found digestate to be the best performing fertilizer because it produced similar yields as the NPK fertilization but minimized nitrate leaching. Legume intercropping increased the total biomass yield by more than 100% compared to S . hermaphrodita single cropping in the fertilized variants. However, it negatively influenced the performance of S . hermaphrodita in the following year. We conclude that a successful establishment of S . hermaphrodita for biomass production in marginal soils is possible and digestate application formed the best fertilization method when considering a range of aspects including overall yield, nitrate leaching, nitrogen fixation of M . sativa , and sustainability over time. [ABSTRACT FROM AUTHOR]