Soil-plant nitrogen isotope composition and nitrogen cycling after biochar applications

• Published in: Environmental science and pollution research international Vol. 28; no. 6; pp. 6684 - 6690
• Main Authors: Asadyar, Leila, Xu, Cheng-Yuan, Wallace, Helen M., Xu, Zhihong, Reverchon, Frédérique, Bai, Shahla Hosseini
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2021; Springer Nature B.V
• Subjects: Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; biochar; Charcoal; Cycles; Earth and Environmental Science; Economics; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; farm profitability; Farms; Fertilizer application; horticulture; Isotope composition; Macadamia; microbial biomass; Microorganisms; Nitrogen; Nitrogen - analysis; Nitrogen cycle; nitrogen fertilizers; Nitrogen Isotopes; Orchards; Photosynthesis; pollution; Profitability; Research Article; Soil; Soils; total nitrogen; Waste Water Technology; Water Management; Water Pollution Control; wood chips; Nitrogen retention; Wood-based biochar; Photosynthesis; Nitrogen isotope composition; Macadamia integrifolia
• ISSN: 0944-1344; 1614-7499; 1614-7499
• DOI: 10.1007/s11356-020-11016-3

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 (δ 15 N) 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 NO 3 − -N increased at months 12 and 24 after biochar application. Soil NO 3 − -N concentrations were always over ideal levels of 15 μg g −1 in B30 throughout the study. Stepwise regression indicated that foliar δ 15 N decreases after biochar application were explained by increased NO 3 − -N concentrations in B30. Foliar TN and photosynthesis were not affected by biochar application. The soil in the high rate biochar plots had excess NO 3 − -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.