Combined biochar and nitrogen application stimulates enzyme activity and root plasticity

Xiaona Song; Bahar S Razavi; Bernard Ludwig; Kazem Zamanian; Huadong Zang; Yakov Kuzyakov; Michaela A Dippold; Anna Gunina

doi:10.1016/j.scitotenv.2020.139393

Combined biochar and nitrogen application stimulates enzyme activity and root plasticity

Sci Total Environ. 2020 Sep 15:735:139393. doi: 10.1016/j.scitotenv.2020.139393. Epub 2020 May 14.

Authors

Xiaona Song¹, Bahar S Razavi², Bernard Ludwig³, Kazem Zamanian⁴, Huadong Zang⁵, Yakov Kuzyakov⁶, Michaela A Dippold⁷, Anna Gunina³

Affiliations

¹ Department of Biogeochemistry of Agroecosystems, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany; Department of Environmental Chemistry, University of Kassel, Nordbahnhofstraße 1a, 37213 Witzenhausen, Germany; College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China.
² Department of Soil and Plant Microbiome, Institute of Phytopathology, University of Kiel, Kiel, Germany.
³ Department of Environmental Chemistry, University of Kassel, Nordbahnhofstraße 1a, 37213 Witzenhausen, Germany.
⁴ Department of Biogeochemistry of Agroecosystems, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany; Department of Agricultural Soil Science, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany.
⁵ College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China. Electronic address: zanghuadong@cau.edu.cn.
⁶ Department of Agricultural Soil Science, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany; Agro-Technology Institute, RUDN University, Moscow, Russia.
⁷ Department of Biogeochemistry of Agroecosystems, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany.

PMID: 32492566
DOI: 10.1016/j.scitotenv.2020.139393

Abstract

Biochar (BC) and nitrogen (N) fertilizers are frequently applied to improve soil properties and increase crop productivity. Nonetheless, our mechanistic understanding of plant-soil interactions under single or combined application of BC and N remains incomplete. For the first time, we applied a split-root system to evaluate how BC or N contributes to the changes in soil enzyme activities, N and phosphorus (P) cycling as well as root plasticity. Left and right parts of rhizoboxes were filled with silty-clay loamy soil amended with BC (15 g kg^-1 soil, from wheat straw, 300 °C), N (0.05 g KNO₃-N kg^-1 soil) or a control (no amendments), resulting in the following combinations: BC/Control, N/Control, BC/N. Soil enzyme activities, available N and P, root morphology and plant biomass were analyzed after plant harvest. Plant biomass (shoot + root) ranged from 0.56 g pot^-1 (BC/Control) to 0.91 g pot^-1(BC/N). The decreased soil bulk density and increased P availability in the BC compartment (BC/Control and BC/N) stimulated root length by 1.4-1.8 times - an effect that was independent of N availability in the same rhizobox. Biochar stimulated activities of β-glucosidase and leucine aminopeptidase (by 33-39%) compared to N due to the coupling of C, N and P cycles in BC/N treated soil. Nitrogen fertilization also increased β-glucosidase activity compared to the unfertilized control, whereas root elongation remained unaffected. Thus, the combined application of BC/N had more efficient benefits for plant growth than BC or N alone. This is linked with i) the stimulation of enzyme activities at the BC locations to reduce N limitation for both microorganisms and plants, and ii) an increase of fine root production to improve N uptake efficiency. Thus, combined BC/N application is potentially especially sustainable to overcome nutrient limitation as well as to maintain crop productivity because it accelerates root-microbial interactions.

Keywords: Microorganisms; Mineral fertilizer; Nutrient cycling; Pyrogenic C; Root morphology; Split-root system.

MeSH terms

Charcoal*
Fertilizers
Nitrogen / analysis*
Soil

Substances

Fertilizers
Soil
biochar
Charcoal
Nitrogen