BonaRes-SIGNAL – Sustainable intensification of agriculture through agroforestry

Project number: 031A562A
Contact: Prof. Dr. Edzo Veldkamp, Univ. Göttingen
Mail: eveldka@gwdg.de
Project team: Universität Göttingen, Universität Kassel, Technische Universität Brandenburg in Cottbus-Senftenberg, Helmholtz Zentrum München, Julius Kühn-Institut (JKI), Thüringer Landesanstalt für Landwirtschaft
Link Website: www.signal.uni-goettingen.de
Duration: 01/07/2015 – 30/06/2018 

Project aim

Central aim of SIGNAL is to evaluate whether and under which site conditions agroforestry in Germany can be a land use alternative that is ecologically, economically and socially more sustainable than conventional agriculture. 

Motivation 
Sustainable intensification of agriculture can be attained if land use systems are designed that combine modern ecological knowledge of the functioning of ecosystems with traditional knowledge on farming. This recognition has stimulated renewed interest in agroforestry since there are several reasons why agroforestry systems are better able to mimic the functioning of natural ecosystems than monoculture crops. Agroforestry systems can have higher nutrient and water use efficiency than annual crops since trees in agroforestry systems can utilize deep nutrients and water outside the rooting zone of annual crops and outside the crop growing season. 

Expected results 

SIGNAL will answer the question whether agroforestry systems are more sustainable than conventional agriculture and thus will increase the land equivalent ratio (LER). The two main criteria that we will use to evaluate this are the efficiency with which nutrients and water are used in agroforestry and conventional systems. We expect that in agroforestry systems a higher input of root and leaf litter of crops, grass and trees will positively influence the composition of the soil community, its functions (litter decomposition, N & P mineralization, N, P, K, Ca, Mg retention), and related soil properties (water holding capacity, aggregate stability) and thus ultimately increase crop yields. 

 

Project results from phase 1

 

Nutrient response efficiency (NRE) describes how efficient plant-available soil nutrients are used (NRE = biomass productivity / unit plant-available nutrient). The combined growth curves and nutrient response efficiency (NRE) curves of agroforestry and conventional systems showed that nutrient availability at studied systems was not limiting plant productivity. From these results, we conclude that presently high fertilization rates that surpass crop demands preclude more optimal NRE values for agroforestry systems. We expect that a significant reduction in applied fertilizer will result in relatively minor reductions in crop yield, but at the same time considerable increases in nutrient response efficiencies.

 

Expected results phase 2

 

Results from the first project phase suggest that concentrations of leached nutrients (especially nitrate) under the tree strips and adjacent cropland are lower than under conventional agriculture. This indicates that nutrient retention of agroforestry systems is higher than in conventional agriculture, which illustrates the potential of agroforestry systems to reduce nitrate losses. Our central hypothesis for phase 2 is hence that establishment of agroforestry systems leads to a quick reduction in nitrate leaching losses compared to conventional agriculture, owing to a combination of effective soil biological mechanisms such as root distribution, production of root exudates, stimulation of denitrification, and N immobilization.