Continuous Cropping Affects Gross Nitrogen Transformations in Subtropical Acidic Soils Under Greenhouse Cultivation
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ORIGINAL PAPER
Continuous Cropping Affects Gross Nitrogen Transformations in Subtropical Acidic Soils Under Greenhouse Cultivation Yongbo Xu 1 & Jingjing Li 2 & Xinhua Yin 3 Received: 24 December 2019 / Accepted: 11 March 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract Relationship between gross N transformation rate and continuous cropping years in the greenhouse soil is largely unknown. This study aimed to investigate the mechanism of the gross N transformation rate changes in greenhouse subtropical acidic soils under different continuous cropping years. The 15N isotope tracer method was used to study the effects of greenhouse soil under 4 years of continuous cropping (C4), 5 years of continuous cropping (C5), and 7 years of continuous cropping (C7) of lily (Lilium brownii), respectively, on soil N transformation with the N tracer model. The results showed that the main soil N transformation processes were N mineralization, autotrophic nitrification, and NO3−-N immobilization under the three continuous cropping years. After continuous cropping, the gross N mineralization rate, autotrophic nitrification rate, and NO3−-N immobilization rate increased with the increase of continuous cropping years. Specifically, the gross N mineralization rate was 0.62~0.85 mg N kg−1 day−1, the autotrophic nitrification rate was 1.08~3.24 mg N kg−1 day−1, and the NO3−-N immobilization rate was 0.30~0.62 mg N kg−1 day−1. Moreover, the positive difference between the autotrophic nitrification rate and immobilization rate of NO3−-N became greater with the increase of continuous cropping years, which might have been the main reason for the accumulation of NO3−-N in greenhouse subtropical soils. These findings contribute to the understanding of the mechanism of soil secondary salinization formation and provide ideas for prevention of secondary salinization under long-term continuous cropping. Keywords Continuous cropping . Gross N transformation rate . Autotrophic nitrification . N mineralization . NO3−-N immobilization . Greenhouse soil
1 Introduction Nitrogen is one of the essential nutrients for plant growth and development. It is also the mineral nutrient that plants take up most from the soil. Nitrogen mainly exists in organic form in soil N pool, while the N uptaken by plants is almost in the inorganic form; so, it is of great significance to understand the N transformation in soil. Soil N transformation is a microbial-mediated process affected by various factors. Fertilization and tillage mode affect the composition and * Xinhua Yin [email protected] 1
College of Tobacco Science, Yunnan Agricultural University, Kunming 650201, Yunnan, China
2
College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, Yunnan, China
3
Department of Plant Sciences, University of Tennessee, Jackson, TN 38301, USA
diversity of soil microbial communities and soil physical and chemical properties, and thus influence the soil N transformation processes (Compton and Boone 2002; Grenon et al. 2004; Jin et al. 20
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