Research activities

Processes and controlling factors of carbon turnover in subsoil

In the research unit "The Forgotten Part of Carbon Cycling: Organic Matter Storage and Turnover in Subsoils (SUBSOM)" funded by the German Research Foundation (DFG), Prof. Dr. Bernd Marschner coordinates the activities of 8 subprojects at different German soil research institutions aiming at  investigating the carbon cycle in the subsoil. Below a depth of 30 cm, more than 50 % of the soil organic carbon store is found, but still, little is known about the turnover and the residence time of these carbon stocks. Therefore, the aim of the research unit is to clarify how a changed climate or a change in land use affects these stocks. For this purpose, the scientists determine the age and composition of different soil organic matter components and carbon flows, and carry out experiments in which temperature, humidity and aeration vary. The results are intended to be used by the ten nationwide working groups for the development of new computer models. A particular challenge in the project is that the carbon concentrations in the subsoil are very low and also very variable in terms of space and time.

 

Food security through soil improvement

As part of the Global Food Security Program (GlobE) funded by the German Ministry of Education and Reseach (BMBF), the project UrbanFoodPLUS is aiming to improve urban and periurban agricultural production systems in four West African cities (Ouagadougou, Burkina Faso; Tamale, Ghana; Bamako, Mali; Bamenda, Cameroon). African food security not only depends on productivity increases in marginal rural areas, but also on a more efficient use of niche environments such as (peri-)urban zones where due to close market linkages between producers and consumers innovations are more easily adopted. There urban and peri-urban agriculture (UPA) covers 5 % to 36 % of a city’s total food supply and up to 90 % of its fresh vegetable consumption. However, little is known about how to overcome problems in resource use efficiencies, negative externalities, and UPA-related income effects on gender or different population groups. The multi-disciplinary UrbanFoodPlus network of German, African, and international scientists, private sector representatives, and stakeholders aims at developing site-specific, farmer-tailored innovations for improved agricultural production, food safety, and value chains in four major West African cities. On-farm experiments, workshops, and policy dialogue will allow to detect bottlenecks in UPA production and marketing chains, and identify and test-implement options to overcome them. An International Graduate School will enhance scientific capacity building and knowledge transfer.

Plant production in sub-Sahara Africa must cope with aridity and low soil fertility, i.e. low availability of plant nutrients, low C contents, low pH and low cation exchange capacity. In many urban and peri-urban areas, high vegetable production is achieved year-round through irrigation with untreated waste water. The nutrient inputs with this irrigation water are beneficial for soil fertility but also may be excessive and thus lead to unproductive losses. In addition, there is a large potential for contamination of soils with pathogens and toxic substances. It is unclear to which degree (1) waste water affects soil fertility and plant growth, (2) negative impacts occur and (3) if sustainable soil fertility can be achieved in these systems through low cost, farmer tailored management options. The "Soil Productivity" subproject aims at filling these research gaps through field and lab experiments. In this context, biochar is being tested as a soil amendment for improving the soil nutrient and water use efficiency and C sequestration. As promising feedstock we are using harvest residues such as rice and maize residues which are usually discarded. UrbanFoodPLUS

 

Influence of fecal sludge and organic municipal solid waste fertilizers on different crops, soils and climate regions throughout Sri Lanka

The project "Evaluation of Fecal Sludge and Municipal Solid Waste Co-Compost as an Agricultural Resource in Sri Lanka" deals with the investigation and evaluation of the application characteristics and effects of fecal sludge and organic municipal solid waste fertilizers on different crops and soils in Sri Lanka. The co-composting of fecal sludge and municipal solid waste produces nutrient-enriched plant compost, which has the potential to replace mineral fertilizers, to enrich soil with organic substance and to help at the same time to deal with municipal waste. The results of the research will primarily support programs aiming at integrating organic waste from municipal sources into recovery and soil improvement processes.