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Article

Grazing under Irrigation Affects N2O-Emissions Substantially in South Africa

1
Institute of Crop Science and Plant Breeding, Grass and Forage Science/Organic Agriculture, Christian-Albrechts-University Kiel, D-24118 Kiel, Germany
2
Department of Agronomy, Stellenbosch University, Stellenbosch 7600, South Africa
*
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(9), 925; https://doi.org/10.3390/atmos11090925
Received: 20 June 2020 / Revised: 13 August 2020 / Accepted: 25 August 2020 / Published: 29 August 2020
Fertilized agricultural soils serve as a primary source of anthropogenic N2O emissions. In South Africa, there is a paucity of data on N2O emissions from fertilized, irrigated dairy-pasture systems and emission factors (EF) associated with the amount of N applied. A first study aiming to quantify direct N2O emissions and associated EFs of intensive pasture-based dairy systems in sub-Sahara Africa was conducted in South Africa. Field trials were conducted to evaluate fertilizer rates (0, 220, 440, 660, and 880 kg N ha−1 year−1) on N2O emissions from irrigated kikuyu–perennial ryegrass (Pennisetum clandestinum–Lolium perenne) pastures. The static chamber method was used to collect weekly N2O samples for one year. The highest daily N2O fluxes occurred in spring (0.99 kg ha−1 day−1) and summer (1.52 kg ha−1 day−1). Accumulated N2O emissions ranged between 2.45 and 15.5 kg N2O-N ha−1 year−1 and EFs for mineral fertilizers applied had an average of 0.9%. Nitrogen in yielded herbage varied between 582 and 900 kg N ha−1. There was no positive effect on growth of pasture herbage from adding N at high rates. The relationship between N balance and annual N2O emissions was exponential, which indicated that excessive fertilization of N will add directly to N2O emissions from the pastures. Results from this study could update South Africa’s greenhouse gas inventory more accurately to facilitate Tier 3 estimates. View Full-Text
Keywords: pasture system; dairy; nitrogen balance; greenhouse gas; emission factors pasture system; dairy; nitrogen balance; greenhouse gas; emission factors
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MDPI and ACS Style

Smit, H.P.J.; Reinsch, T.; Swanepoel, P.A.; Kluß, C.; Taube, F. Grazing under Irrigation Affects N2O-Emissions Substantially in South Africa. Atmosphere 2020, 11, 925. https://doi.org/10.3390/atmos11090925

AMA Style

Smit HPJ, Reinsch T, Swanepoel PA, Kluß C, Taube F. Grazing under Irrigation Affects N2O-Emissions Substantially in South Africa. Atmosphere. 2020; 11(9):925. https://doi.org/10.3390/atmos11090925

Chicago/Turabian Style

Smit, Hendrik P.J., Thorsten Reinsch, Pieter A. Swanepoel, Christof Kluß, and Friedhelm Taube. 2020. "Grazing under Irrigation Affects N2O-Emissions Substantially in South Africa" Atmosphere 11, no. 9: 925. https://doi.org/10.3390/atmos11090925

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