Research Group: Soil Fertility

 

Soil organic matter, soil quality and nutrient turnover

The Soil Fertility research group has a strong tradition for research on biological soil fertility and the influence of organic matter decomposition processes on nutrient turnover in temperate zone agro-ecosystems. A particular focus area has been the interaction between plant and soil in the root rhizosphere, as well as the role of the soil microbial biomass in determining nutrient availability. Over the past decades, our research focus has been widened to also cover soil fertility and nutrient dynamics in agricultural systems of lesser developed countries.

Our research platform on soil organic matter, nutrient turnover, and soil fertility is closely related to our research platform on agricultural and urban waste, and shares central competences on organic matter decomposition and nutrient turnover, see figure. The research is focused on:

 

Fundamental processes and factors controlling the decomposition of organic matter, nutrient turnover and soil quality in the short and long term.  Soil carbon nitrogen and phosphorous dynamics are studied using isotopic tracer techniques (stable 15N, 13C, radioactive 14C, 32P) and the lab has its own CF-IRMS facility. Methods for physical fractionation of both recalcitrant soil organic matter (oxidative chemical and thermal treatments, combined with NIR, NMR and ) and more recently added organic matter (density and size separation, combined with tracers) are developed and tested. Plant litter quality effects on decomposition and nitrogen release has been studied intensively in a number of projects, and new spectroscopic techniques (NIR, chemometrics) for residue quality characterisation have been developed and are being extended for other materials as well (straw, manure). New cross-disciplinary work, combining molecular techniques (eg. DGGE) for microbial community and soil quality characterisation and modelling with our more traditional process understanding, has been instigated. The work is linked with cropping systems science and plant nutritional physiology, with the aim of improving the crop utilization of nutrients derived from both soil and applied fertilisers and manures.

 

Model development of soil organic matter and nutrient turnover, where the group has been partners in the development, validation and application of the soil-plant-atmosphere model Daisy, in particular for scenario analyses of e.g. long-term effects of straw removal or sewage sludge application on soil carbon sequestration. Work is also on-going to develop a soil organic matter model built on continuous organic matter quality distributions, and coupling this with new methods for organic matter characterisation (SPLITT, FFF, DGC).  

 

Biogeochemical processes controlling nutrient and contaminant availability and mobility. Assessment of nutrient and trace element (incl. xenobiotics as heavy metals) availability is essential to ensure that the quality and quantity of the food production is maintained, but our ability to assess plant nutrient availability and the potential for nutrient leaching from soil is still significantly limited. Work is therefore on-going to develop new methods (DGT) to simultaneously assess the availability of a range of nutrients and other trace elements, but also to increase our mechanistic understanding and predictability of e.g. phosphorus leaching through soil.

 

 

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Utilisation of agricultural and urban waste as fertilizer

With the exponential growth of industrialised animal production, both in developed countries like Denmark and in many developing countries (SE Asia), animal manure is becoming a major waste product, requiring safe, sustainable and sanitary management.  Urban waste management approaches are also undergoing rapid changes, which have particular impacts on nutrient cycling opportunities in lesser developed countries.  When waste is utilised on arable land, its fertilizer value and effects on soil quality should be optimised and negative effects of xenobiotics and pathogens on ecosystem and human health should be eliminated.
Our research platform on improved utilisation of agricultural and urban waste as fertilizer is closely related to our research on soil fertility, and shares central competences on organic matter decomposition and nutrient turnover, see figure. The research is focused on:

 

Land application of animal manures and other waste products from agriculture, industry and society and their fertiliser value and effects on soil quality (carbon, nutrients, heavy metal, xenobiotics) as well as gaseous emissions and nutrient losses to the environment (ammonia, nitrous oxide, methane, nitrate and phosphorous leaching). Nutrient turnover and fertiliser value from the manure is studied using isotopic techniques (15N tracing, pool dilution) and also includes field experimental approaches in both Denmark and developing countries. Determination of manure and waste properties relevant for nutrient availability (VFA, solubles) but also for the risk of leaching of contaminants (pathogens, medicines, hormones) to freshwater, are studied using a range of techniques (NIR, SCD, SEM etc.).

 

Methods for biological treatment of organic waste and residue materials and refinement into products of higher-value (e.g. soil conditioners, top-dressings) or energy (e.g. bioethanol, fuel).  Crucial to this work is the characterisation of the waste materials in terms of their degradability and recalcitrance to decomposition, which in term is quantified by the range of techniques mentioned above. Efficient management of organic waste requires technology development (manure separation, wastewater treatment, anaerobic digestion, field application etc.) for optimal utilisation of these resources, whether it is for crop fertilisation, soil quality improvement, CO2 sequestration or bio-energy production (incineration, methane, bio-fuel). We therefore prioritise close collaboration with technical research groups, both within Univ. of Copenhagen, but also with the Danish Technical University and the University of Southern Denmark. Finally, we consider the assessment of the environmental sustainability of the various technical and agronomic solutions to be an essential part of our research, and a priority development area for us is therefore Life Cycle Assessment (LCA) of various waste utilisation schemes with respect to environmental and global change impact.

 

Nutrient recycling of human waste from cities to agriculture in peri-urban areas of both temperate and tropical climates, and development of systems that are environmentally sustainable also in the long term. As one of our major efforts in this area, we have established a long-term field experimental facility, the CRUCIAL long-term field site with urban fertilizers and organic amendments to test agronomic and environmental impacts on soil, water and plant quality. In this field-site, initiated in 2002, urban fertilisers (waste products) such as degassed sewage sludge, composted organic household waste and human urine are applied in fixed treatment plots and compared with both mineral fertilizer and conventional organic manures. The site will provide opportunity for a range of studies into the effect of these controversial waste materials on sol quality, key soil microbial and ecological functions as well as impact on animal and human health through the crops grown on the site.

 

Please contact Professor Lars Stoumann Jensen for further information.