Autor:innen:
Mehdi Rashtbari | Department of Soil and Plant Microbiome, Institute of Phytopathology, University of Kiel, Germany | Germany
Andrea Braun-Kiewnick | Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn-Institute - Federal Research Centre for Cultivated Plants, Germany | Germany
Markus Schemmel | Department for Molecular Phytopathology and Biotechnology, Institute of Phytopathology, University of Kiel, Germany | Germany
Zheng Zhou | Germany
Lingyue Han | Germany
Katharina Pronkow | Department of Agronomy and Crop Science, Christian Albrechts University of Kiel, Kiel, Germany | Germany
Doreen Babin | Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn-Institute - Federal Research Centre for Cultivated Plants, Germany
Kornelia Smalla | Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn-Institute - Federal Research Centre for Cultivated Plants, Germany | Germany
Daguang Cai | Department for Molecular Phytopathology and Biotechnology, Institute of Phytopathology, University of Kiel, Germany | Germany
Henning Kage | Department of Agronomy and Crop Science, Christian Albrechts University of Kiel, Kiel, Germany | Germany
Bahar S. Razavi | Department of Soil and Plant Microbiome, Institute of Phytopathology, University of Kiel, Germany | Germany
Continuous wheat cultivation leads to crop productivity decrease. Soil carbon availability is one of the main determinants of microbial activity. Also, nitrogen (N) availability limits plant growth in most terrestrial ecosystems, regulates carbon sequestration and microbial functionality. Therefore, this study aims to elucidate and quantify the effects of the first and second wheat after break crop and long-term wheat monoculture at late growth stage, on soil enzymatic activity. We hypothesized that the long-term wheat rotation leads to the production of less efficient enzymes accompanied by the decline of enzyme production. We performed spatio-temporal sampling in frame of a field study at the experimental farm Harste, (IFZ, Göttingen). A horizontal soil sampling from rhizosphere (RH), root affected soil (RA), and bulk soil (BS), at the flowering stage (BBCH 69-71) as 1st (W1) and 2nd (W2) wheat after break crop and wheat monoculture (WM) was performed. The kinetic parameters (Vmax and Km) of β-glucosidase involved in degradation of C substances and L-leucine aminopeptidase (LAP) involved in nitrogen acquisition were determined. Results showed there was considerable decrease in Vmax in WM compared to W1 and W2 in RH and RA compartments for β-glucosidase and in RA for LAP. The highest decrease in wheat monoculture compared to the W1 was observed in RH by ~34 % for β-glucosidase and 26.2 % in BS for β-glucosidase. The lowest Vmax for LAP was observed in RA in W2 which was the same as WM and decreased by ~48 %. The substrate affinity (Km) for β-glucosidase in BS and RA strongly decreased in WM compared to W1 and W2, while in RH a 38 and 18.6 % increase was observed in W2 and WM compared to W1, respectively. For LAP, Km values showed increasing trend from W1 to W2 and WM in BS and RH. Catalytic efficiency (Vmax/Km) for β-glucosidase and LAP in RH compartment showed considerable decrease in WM compared to W1 by 42.6 and 41.3 %, respectively. The general trend of catalytic efficiency demonstrated a gradual decrease with wheat rotation as a function of distance from root to bulk soil. Overall results showed that RH compartment had the highest enzyme activity and there was a downward trend from rhizosphere to bulk soil compartments for enzyme activities. We concluded that continuous cultivation of wheat suppressed microbial activity and functional efficiency and not only resulted to lower enzyme activity, but also led to production of less efficient enzymes.