Mitigating runoff nitrate loss from soil organic nitrogen mineralization in citrus orchard catchments using green manure

Yue Luo; Xian Wu; Ji Liu; Hengbin Xiao; Bin Liao; Ronggui Hu

doi:10.1016/j.watres.2023.120398

Mitigating runoff nitrate loss from soil organic nitrogen mineralization in citrus orchard catchments using green manure

Water Res. 2023 Sep 1:243:120398. doi: 10.1016/j.watres.2023.120398. Epub 2023 Jul 22.

Authors

Yue Luo¹, Xian Wu¹, Ji Liu², Hengbin Xiao¹, Bin Liao³, Ronggui Hu⁴

Affiliations

¹ College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
² Hubei Province Key Laboratory for Geographical Process Analysis and Simulation, Central China Normal University, Wuhan 430079, China; Department of Ecohydrology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin 12587, Germany.
³ School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan 430072, China.
⁴ College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: rghu@mail.hzau.edu.cn.

PMID: 37506633
DOI: 10.1016/j.watres.2023.120398

Abstract

Nitrate-nitrogen (NO₃^--N) loss is a significant contributor to water quality degradation in agricultural catchments. The amount of nitrogen (N) fertilizer input in citrus orchard is relatively large and results in significant NO₃^--N loss, compared to cropland. To promote sustainable N fertilizer management, it is crucial to identify the sources of runoff NO₃^--N loss in citrus orchards catchments. Particularly, we poorly know the sources of NO₃^--N and the mitigation mechanisms in these areas, which are highly polluted with NO₃^--N in water bodies. In this study conducted in central China, we conducted a field experiment with four treatments (CK: no N fertilizer; CF: conventional N fertilizer, 371.3kg N ha^-1 yr^-1 urea; OM: CF with organic manure; GM: CF with legume green manure) and a catchment-scale experiment in two citrus orchards (34.3%; 51.6%) catchments. To determine the source of runoff NO₃^--N loss, we used the dual isotope tracer method (δ¹⁵N and δ¹⁸O of NO₃^-) to identify the sources of NO₃^--N, and a 15-day incubation experiment to determine the potential and rate of soil N mineralization. Our findings revealed that soil organic nitrogen (SON) mineralization was the primary contributor to runoff NO₃^--N loss, and soil N mineralization potential (0.65^⁎⁎⁎) and rate (0.54^⁎⁎⁎) were the key factors impacting NO₃^--N loss. Interestingly, organic manure significantly increased 29.0% of NO₃^--N loss derived from SON in the runoff by enhancing soil N mineralization potential (+36.6%) and rate (+77.1%). But green manure mulching significantly reduced the soil N mineralization rate (-18.6%) compared to organic manure application, making it the most effective measure to reduce NO₃^--N loss (-12.4%). Our study highlights the critical role of regulating SON mineralization in controlling NO₃^--N pollution in surface waters in citrus orchard catchments.

Keywords: Agricultural catchment; Citrus orchard; Nitrate-nitrogen loss; Soil nitrogen mineralization; Soil organic nitrogen.

MeSH terms

Agriculture
China
Environmental Monitoring / methods
Fertilizers / analysis
Manure / analysis
Nitrates / analysis
Nitrogen* / analysis
Organic Chemicals
Soil
Water Pollutants, Chemical* / analysis

Substances

Nitrogen
Soil
Nitrates
Manure
Fertilizers
Water Pollutants, Chemical
Organic Chemicals