FOR 1320:  Crop Sequence and the Nutrient Acquisition from the Subsoil

• Subject Area: Agriculture, Forestry and Veterinary Medicine
• Term: from 2010 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 135946177

The Research Unit aims to describe and quantify processes of nutrient release in the agricultural subsoil, highlighting the creation of biopore systems, soil structure dynamics, microbial activities, water dynamics and nutrient transformation processes.
A field trial, consisting of two series, has been established on a deep loess soil. Three forage precrop species with different root systems have been chosen in order to generate biopores of different size and density in the subsoil. The biopore systems, we assume, depend besides the species driven effect on their cultivation time (one to three years). On-site research and a number of non-invasive techniques (CT, EIT, NMR-methods, PET and adapted endoscopy) will be used and calibrated with standard reference methods to quantify soil structure, water dynamics and root growth.
Isotope labelling will quantify the partitioning of photoassimilates to the root systems, as well as the spatial distribution of rhizodeposits (13C). Soil-compartment experiments will allow to analyse basic processes of plant-induced P and K mobilisation. The dynamics of microbial community structure and their function over time, as well as the function of the biopores as a habitat for specific microbial communities, will be quantified. Microcosm experiments will enable to describe the part of the microbial community that has utilised an applied 13C carbon source.
Nutrient mobilisation from organic residues will be investigated by using 13C-, 14C-, 15N- und 33P- and P18O- labelled substrates. Sequential extractions, liquid-state-31P-NMR spectroscopy and electron microprobe analyses will be used to elucidate the P forms in different soil compartments. A number of these samples are also characterised with regard to their colonisation by AMF mycorrhizae. The uptake of P from labelled biopores will be assessed using the 33P radioisotope. 15N labelled plant residues, as well as 15NO3, will be used in order to improve our understanding of the role of non-exchangeable NH4+ in the subsoil for the N nutrition of crops.
In a two-step approach, results from the different subprojects, which quantify the biopore system, the soil nutrient pools and nutrient fluxes, will be used to develop plant- and field-scale models based on the respective different process models. It is expected that this research programme will contribute to the efficient use of subsoil nutrient resources in future sustainable agricultural systems.

• DFG Programme: Research Units

Projects

• Bioaccessibility of phosphorus in the subsoil (SubsoilP) (Applicant Amelung, Wulf )
• Biopores in the subsoil: Formation, nutrient turnover and effects on crops with distinct rooting systems (BioFoNT) (Applicant Köpke, Ulrich )
• Dynamics of soil structure and physical soil functions and their importance for the acquisition of nutrients from the subsoil (Applicant Horn, Rainer )
• Microbial community structure and function in different habitats of subsoils and their role in nutrient mobilization and plant growth (MicroSub) (Applicant Munch, Jean Charles )
• Modelling nutrient acquisition from the sub-soil for different crops with specific consideration of bio-pores (NutrAcMod) (Applicant Ewert, Frank )
• Modelling root uptake processes in heterogeneous soils at the plant scale with a specific attention to biopores and rhizosphere impact on nutrient acquisition (Applicant Vanderborght, Jan )
• Non-destructive characterization and monitoring of root structure and function at the rhizotron and field scale using spectral electrical impedance tomography (ImpTom) (Applicants Kemna, Andreas ;  Walter, Achim )
• Non-exchangeable NH4-N in the subsoil:Significance for the N nutrition of plants (NitroNex) (Applicant Scherer, Heinrich Wilhelm )
• Plant induced weathering of minerals in the subsoil - release of 'non-exchangeable' potassium from 2:1 layer minerals (TransMinK) (Applicant Jahn, Reinhold )
• Rhizodeposition is the main source of carbon and energy for nutrient mobilization in subsoil (RhizoCNP) (Applicant Kuzyakov, Yakov )
• Water as medium for nutrient distribution: Monitoring water distribution between subsoil and topsoil considering roles of biopores and plants, by MRT and pressure probes (WatMed) (Applicant Schneider, Heike )

• Spokesperson: Professor Dr. Ulrich Köpke