Kinetics of amino sugar formation from organic residues of different quality

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Agronomic efficiency of selected phosphorus fertilisers derived from secondary raw materials for European agriculture. A meta-analysis

International audiencePhosphorus (P) is a macronutrient essential for all living organisms. Food production has become highly dependent on mineral P-fertilisers derived from phosphate rock, a non-renewable and finite resource. Based on supply risk and economic importance for the European Union, phosphate rock and elemental P have been identified as critical raw materials. Moreover, P dissipation can lead to adverse impacts on the aquatic environment. The production and use of P-fertilisers derived from secondary raw materials could possibly contribute to a more sustainable agriculture in line with a circular economy. Biogenic and industrial resources and waste streams can be converted into value added materials, such as precipitated phosphate salts, thermal oxidation materials and derivates, and pyrolysis and gasification materials. A condition is, however, that the P must be recovered in a plant-available form and that the recovered P-fertiliser supports plant growth and nutrient uptake in European agroecosystems. Here, we review the agronomic efficiency of selected P-fertilisers derived from secondary raw materials by comparing plant responses relative to those after mined and synthetic P-fertiliser application in settings relevant for European agriculture, using meta-analyses. The major points are the following: (1) precipitated phosphate salts show similar agronomic efficiency to mined and synthetic P-fertilisers, with results that are consistent and generalisable across soil and crop types relevant for European agriculture; (2) thermal oxidation materials and derivates can deliver an effective alternative for mined and synthetic P-fertilisers, but the relative agronomic efficiency is dependent on the feedstock applied, possible post-combustion manufacturing processes, and the length of the plant growing season; (3) the agronomic efficiency of pyrolysis and gasification materials remains indeterminate due to a lack of available data for European settings. It is concluded that the agronomic efficiency of selected P-fertilisers derived from secondary raw materials supports their use in conventional and organic European agricultural sectors

Hydrological controls on nutrient exportation from old-growth evergreen rainforests and Eucalyptus nitens plantation in headwater catchments at Southern Chile

Soil cover disturbances have a direct effect on biogeochemistry, potentially enhancing nutrient loss, land degradation and associated changes in ecosystem services and livelihood support. The objective of this study was to assess how canopy affected throughfall chemistry and how hydrology affected stream nutrient load responses in two watersheds dominated by native old-growth evergreen rainforest (NF) and exotic plantation of Eucalyptus nitens (EP), located at the Coastal mountain range of southern Chile (40˚S). We measured nitrogen (NO3-N, NH4-N, Organic-N, Total-N) and total phosphorus (Total-P) at catchment discharge, and δ18O in throughfall precipitation and stream discharge in both catchments, in order to separate throughfall (or new water) contributions during storm events. It was hypothesized that all nutrients showed an increase in concentration as discharge increased (or enhanced hydrological access), in EP; but not in NF. Our results indicated that Organic-N, Total-N and Total-P concentrations were positively related to discharge. However, 3 NO− -N showed a negative correlation with catchment discharge

Advances in N-15-tracing experiments: new labelling and data analysis approaches

To obtain an in-depth understanding of soil nitrogen dynamics, it is necessary to quantify a variety of simultaneously occurring gross nitrogen transformation processes. In order to do so, most studies apply N-15 in a disturbed soil-microbial-root system and quantify gross rates based on the principles of N-15 isotope dilution. However, this approach has several shortcomings. First, studying disturbed soil provides only limited information on in situ soil nitrogen dynamics. Secondly, the analytical data analysis allows the quantification of total production and consumption rates of the labelled pool, but does not provide information on process-specific transformation rates. Combining in situ N-15 isotope labelling over 1-2 weeks with numerical data analysis allows determining process-specific gross nitrogen transformations in undisturbed soils under field conditions in the presence of live roots and their associated microbial communities. This has the potential to increase our understanding of nitrogen dynamics in the soil environment