Spatial trends in the nitrogen budget of the African agro-food system over the past five decades

Abstract

Low nitrogen (N) fertilization is a dominant cause of malnutrition in Africa, but the spatial and temporal variability of N cycling patterns in Africa remain unclear. This study is the first to perform a detailed analysis of the N cycling patterns of 52 African countries from 1961 to 2016. We calculated the N use efficiency (NUE) in crop production, country-specific N fertilization trends, and the impacts of N fertilization on human protein demand and the environment. Over the past five decades, total N input to African croplands increased from 20 to 35 kg N ha −1 yr −1 , while the application of synthetic N fertilizers (SNF) increased from 4.0 to 15 kg N ha −1 yr −1 . N contributions from animal manure and biological N fixation remained lower than 10 kg N ha −1 yr −1 and 20 kg N ha −1 yr −1 , respectively. The total N crop production increased from 15 to 22 kg N ha −1 yr −1 from 1961 to 2016. Total N surplus in Africa increased from 5 to 13 kg N ha −1 yr −1 , while estimated gaseous losses increased from 4.0 to 11 kg N ha −1 yr −1 . However, NUE declined from 74% to 63% during the past five decades, and protein consumption increased from 2.99 to 3.78 kg N capita −1 yr −1 . These results suggest that Africa suffers from extremely low N input and that N loss is increasing in agricultural land. We recommend the implementation of an effective N management strategy incorporating the use of locally available organic material along with the balanced application of SNF. Such measures will require effective policy development and cooperation between all stakeholders. Acronyms and abbreviationsOPEN ACCESS RECEIVED

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

“…Soil N depletion through different channels exceeds TNI (ANM, BNF, AND, and SNF) in Rwanda (Figure 10); the same issue was noticed by Elrys et al (2019a). FP profits from soil mining even though soil fertility and environmental wellness are lost by mobilizing Nr (Hutton et al, 2017;Masso et al, 2017).…”

“…Due to that improper manure management and poor use of animal feed quality (Diogo et al, 2013), only a few quantities of livestock excrements are applied to cropland as ANM. Generally, policymakers in Africa are uninterested in using organic manure for cropping (Ciceri and Allanore, 2019), which has caused poor purchasing power and lower accessibility of good quality fertilizers (Elrys et al, 2019a).…”

“…Due to longtime companion with soil mining of N, it is necessary to raise the rate of SNF and the overall number of farmers applying fertilizer on their farms to prevent future crop failure. The low rate of N recovered from applied N fertilizer, ranging from 10 to 20% (Chianu et al, 2012), demoralizes small farmers from buying quality fertilizers in Africa (Woomer et al, 2008;Elrys et al, 2019a). Therefore, we should execute fair use of N input principles, such as using appropriate SNF and applying it at the proper rate, time, and place (Johnston and Bruulsema, 2014;Yuan and Peng, 2017).…”

“…Investment in food marketing infrastructures such as roads, market facilities, and electricity can motivate operations along agricultural supply chains (Sheahan and Barrett, 2017). For sustainable agriculture and alleviating depressing impacts on human health and the environment, appropriate management practice measures should focus on raising the TNI to cropland and promoting NUE (Zhang et al, 2015;Hutton et al, 2017;Yuan and Peng, 2017;Elrys et al, 2019aElrys et al, , 2019b. Therefore, it is essential to estimate NF food to identify food products that induce high loss of N through soil mining/depletion and gaseous emission.…”

“…A soil test can be done prior to planting to determine the quantity of external fertilizers that will be needed to produce a potential yield. Moreover, cropping varieties of enhanced NUE can read to maximum yields for poor farmers that cannot afford SNF in high quality easily (Elrys et al, 2019a). A comprehensive and adequate FP system requires integrated farming management practices that minimize N fertilizer losses to water bodies and the air (Elrys et al, 2021b).…”