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

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Asadyar, L
Xu, CY
Wallace, HM
Xu, Z
Reverchon, F
Bai, SH
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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.

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Environmental Science and Pollution Research

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Chemical sciences

Horticultural production

Soil chemistry and soil carbon sequestration (excl. carbon sequestration science)

Macadamia integrifolia

Nitrogen isotope composition

Nitrogen retention


Wood-based biochar

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Asadyar, L; Xu, CY; Wallace, HM; Xu, Z; Reverchon, F; Bai, SH, Soil-plant nitrogen isotope composition and nitrogen cycling after biochar applications, Environmental Science and Pollution Research, 2020