Soil-plant nitrogen isotope composition and nitrogen cycling after biochar applications
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RESEARCH ARTICLE
Soil-plant nitrogen isotope composition and nitrogen cycling after biochar applications Leila Asadyar 1 & Cheng-Yuan Xu 2 & Helen M. Wallace 1 & Zhihong Xu 1 & Frédérique Reverchon 3 & Shahla Hosseini Bai 1 Received: 24 April 2020 / Accepted: 25 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Biochar has strong potential to improve nitrogen (N) use efficiency in both agricultural and horticultural systems. Biochar is usually co-applied with full rates of fertiliser. However, the extent to which N cycling can be affected after biochar application to meet plant N requirement remains uncertain. This study aimed to explore N cycling up to 2 years after biochar application. We applied pine woodchip biochar at 0, 10 and 30 t ha−1 (B0, B10, B30, respectively) in a macadamia orchard and evaluated the N isotope composition (δ15N) of soil, microbial biomass and macadamia leaves. Soil total N (TN) and inorganic N pools were also measured up to 2 years after biochar application. Biochar did not alter soil TN but soil NO3−-N increased at months 12 and 24 after biochar application. Soil NO3−-N concentrations were always over ideal levels of 15 μg g−1 in B30 throughout the study. Stepwise regression indicated that foliar δ15N decreases after biochar application were explained by increased NO3−-N concentrations in B30. Foliar TN and photosynthesis were not affected by biochar application. The soil in the high rate biochar plots had excess NO3−-N concentrations (over 30 μg g−1) from month 20 onwards. Therefore, N fertiliser applications could be adjusted to prevent excessive N inputs and increase farm profitability. Keywords Photosynthesis . Wood-based biochar . Nitrogen retention . Nitrogen isotope composition . Macadamia integrifolia
Introduction It is predicted that the world population will rise to 9.5 billion by 2050 (Lal 2015). Consequently, the agricultural production will need to increase by approximately 70% (Lal 2015), which will likely enhance soil degradation and exploitation (Delong et al. 2015). Currently, cultivated areas cover approximately 37% of terrestrial lands (World Bank 2016), but 25% of these Responsible Editor: Philippe Garrigues Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-11016-3) contains supplementary material, which is available to authorized users. * Shahla Hosseini Bai [email protected] 1
Environmental Futures Research Institute, School of Environment and Science, Griffith University, 170 Kessels Rd, Nathan, QLD 4111, Australia
2
School of Health, Medical and Applied Sciences, Central Queensland University, Bundaberg, QLD 4760, Australia
3
Red de Estudios Moleculares Avanzados, Instituto de Ecología A.C., Pátzcuaro, Michoacán, Mexico
agricultural lands have already been highly degraded (FAO 2011). Depletion of soil nitrogen (N) and organic carbon (OC) are two of the major soil issues globally (Lal 2015). Thus, developing novel agricultural management practices to min
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