Estimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures

This study presents the first detailed estimate of Rwanda’s nitrogen (N) flows and N footprint for food (NFfood) from 1961 to 2018. Low N fertilizer inputs, substandard production techniques, and inefficient agricultural management practices are focal causes of low crop yields, environmental polluti...

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Autores principales:	Barthelemy Harerimana, Minghua Zhou, Muhammad Shaaban, Bo Zhu
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	nitrogen loss agro-food system soil nitrogen mining nitrogen footprint virtual nitrogen factor nitrogen use efficiency Environmental sciences GE1-350
Acceso en línea:	https://doaj.org/article/8461714696444c1baabc9d765c258d4d
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spelling	oai:doaj.org-article:8461714696444c1baabc9d765c258d4d2021-12-01T08:11:08ZEstimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures2296-665X10.3389/fenvs.2021.778699https://doaj.org/article/8461714696444c1baabc9d765c258d4d2021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fenvs.2021.778699/fullhttps://doaj.org/toc/2296-665XThis study presents the first detailed estimate of Rwanda’s nitrogen (N) flows and N footprint for food (NFfood) from 1961 to 2018. Low N fertilizer inputs, substandard production techniques, and inefficient agricultural management practices are focal causes of low crop yields, environmental pollution, and food insecurity. We therefore assessed the N budget, N use efficiency (NUE), virtual N factors (VNFs), soil N mining factors (SNMFs), and N footprint for the agro-food systems of Rwanda with consideration of scenarios of fertilized and unfertilized farms. The total N input to croplands increased from 14.6 kg N ha−1 yr−1 (1960s) to 34.1 kg N ha−1 yr−1 (2010–2018), while the total crop N uptake increased from 18 kg N ha−1yr−1 (1960s) to 28.2 kg N ha−1yr−1 (2010–2018), reflecting a decline of NUE from 124% (1960s) to 85% (2010–2018). Gaseous N losses of NH3, N2O, and NO increased from 0.45 (NH3), 0.03 (N2O), and 0.00 (NO) Gg N yr−1 (1960s) to 6.98 (NH3), 0.58 (N2O), and 0.10 (NO) Gg N yr−1 (2010–2018). Due to the low N inputs, SNMFs were in the range of 0.00 and 2.99 and the rice production, cash-crop production, and livestock production systems have greater SNMFs in Rwanda. The weighted NFfood per capita that presents the actual situation of fertilized and unfertilized croplands increased from 4.0 kg N cap−1 yr−1 (1960s) to 6.3 kg N cap−1 yr−1 (2010–2018). The NFfood per capita would increase from 3.5 kg N cap−1 yr−1 to 4.8 kg N cap−1 yr−1 under a scenario of all croplands without N fertilizer application and increase from 6.0 to 8.7 kg N cap−1 yr−1 under the situation of all croplands receiving N fertilizer. The per capita agro-food production accounted for approximately 58% of the national NFfood. The present study indicates that Rwanda is currently suffering from low N inputs, high soil N depletion, food insecurity, and environmental N losses. Therefore, suggesting that the implementation of N management policies of increasing agricultural N inputs and rehabilitating the degraded soils with organic amendments of human and animal waste needs to be carefully considered in Rwanda.Barthelemy HarerimanaBarthelemy HarerimanaMinghua ZhouMuhammad ShaabanBo ZhuFrontiers Media S.A.articlenitrogen lossagro-food systemsoil nitrogen miningnitrogen footprintvirtual nitrogen factornitrogen use efficiencyEnvironmental sciencesGE1-350ENFrontiers in Environmental Science, Vol 9 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	nitrogen loss agro-food system soil nitrogen mining nitrogen footprint virtual nitrogen factor nitrogen use efficiency Environmental sciences GE1-350
spellingShingle	nitrogen loss agro-food system soil nitrogen mining nitrogen footprint virtual nitrogen factor nitrogen use efficiency Environmental sciences GE1-350 Barthelemy Harerimana Barthelemy Harerimana Minghua Zhou Muhammad Shaaban Bo Zhu Estimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures
description	This study presents the first detailed estimate of Rwanda’s nitrogen (N) flows and N footprint for food (NFfood) from 1961 to 2018. Low N fertilizer inputs, substandard production techniques, and inefficient agricultural management practices are focal causes of low crop yields, environmental pollution, and food insecurity. We therefore assessed the N budget, N use efficiency (NUE), virtual N factors (VNFs), soil N mining factors (SNMFs), and N footprint for the agro-food systems of Rwanda with consideration of scenarios of fertilized and unfertilized farms. The total N input to croplands increased from 14.6 kg N ha−1 yr−1 (1960s) to 34.1 kg N ha−1 yr−1 (2010–2018), while the total crop N uptake increased from 18 kg N ha−1yr−1 (1960s) to 28.2 kg N ha−1yr−1 (2010–2018), reflecting a decline of NUE from 124% (1960s) to 85% (2010–2018). Gaseous N losses of NH3, N2O, and NO increased from 0.45 (NH3), 0.03 (N2O), and 0.00 (NO) Gg N yr−1 (1960s) to 6.98 (NH3), 0.58 (N2O), and 0.10 (NO) Gg N yr−1 (2010–2018). Due to the low N inputs, SNMFs were in the range of 0.00 and 2.99 and the rice production, cash-crop production, and livestock production systems have greater SNMFs in Rwanda. The weighted NFfood per capita that presents the actual situation of fertilized and unfertilized croplands increased from 4.0 kg N cap−1 yr−1 (1960s) to 6.3 kg N cap−1 yr−1 (2010–2018). The NFfood per capita would increase from 3.5 kg N cap−1 yr−1 to 4.8 kg N cap−1 yr−1 under a scenario of all croplands without N fertilizer application and increase from 6.0 to 8.7 kg N cap−1 yr−1 under the situation of all croplands receiving N fertilizer. The per capita agro-food production accounted for approximately 58% of the national NFfood. The present study indicates that Rwanda is currently suffering from low N inputs, high soil N depletion, food insecurity, and environmental N losses. Therefore, suggesting that the implementation of N management policies of increasing agricultural N inputs and rehabilitating the degraded soils with organic amendments of human and animal waste needs to be carefully considered in Rwanda.
format	article
author	Barthelemy Harerimana Barthelemy Harerimana Minghua Zhou Muhammad Shaaban Bo Zhu
author_facet	Barthelemy Harerimana Barthelemy Harerimana Minghua Zhou Muhammad Shaaban Bo Zhu
author_sort	Barthelemy Harerimana
title	Estimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures
title_short	Estimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures
title_full	Estimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures
title_fullStr	Estimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures
title_full_unstemmed	Estimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures
title_sort	estimating nitrogen flows and nitrogen footprint for agro-food system of rwanda over the last five decades: challenges and measures
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/8461714696444c1baabc9d765c258d4d
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Estimating Nitrogen Flows and Nitrogen Footprint for Agro-Food System of Rwanda Over the Last Five Decades: Challenges and Measures

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