The fate of nitrogen during agricultural intensification in East Africa: nitrogen budgets in contrasting agroecosystems

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cg.authorship.typesCGIAR and developing country instituteen
cg.contributor.affiliationUniversity of Marylanden
cg.contributor.affiliationColumbia Universityen
cg.contributor.affiliationPennsylvania State Universityen
cg.contributor.affiliationWoodwell Climate Research Center, USAen
cg.contributor.affiliationTanzania Agricultural Research Instituteen
cg.contributor.affiliationInternational Labour Organizationen
cg.contributor.affiliationInternational Institute of Tropical Agricultureen
cg.contributor.affiliationUniversity of Floridaen
cg.contributor.donorEarth Institute at Columbia Universityen
cg.contributor.donorNational Science Foundationen
cg.contributor.donorBill & Melinda Gates Foundationen
cg.coverage.countryKenya
cg.coverage.countryTanzania
cg.coverage.iso3166-alpha2KE
cg.coverage.iso3166-alpha2TZ
cg.coverage.regionAfrica
cg.coverage.regionEastern Africa
cg.creator.identifierKatherine Tully: 0000-0002-6190-2679
cg.creator.identifierJonathan Hickman: 0000-0002-7246-642X
cg.creator.identifierPatick Mutuo: 0000-0002-9824-2504
cg.howPublishedFormally Publisheden
cg.identifier.doihttps://doi.org/10.1029/2022jg007128en
cg.isijournalISI Journalen
cg.issn2169-8953en
cg.issue7: e2022JG007128en
cg.journalJournal of Geophysical Research: Biogeosciencesen
cg.reviewStatusPeer Reviewen
cg.subject.iitaFOOD SECURITYen
cg.subject.iitaLIVELIHOODSen
cg.subject.iitaSMALLHOLDER FARMERSen
cg.subject.impactAreaNutrition, health and food security
cg.subject.sdgSDG 2 - Zero hungeren
cg.volume128en
dc.contributor.authorTully, Katherine L.en
dc.contributor.authorHickman, J.E.en
dc.contributor.authorRusso, T.A.en
dc.contributor.authorNeill, C.en
dc.contributor.authorMatata, P.en
dc.contributor.authorNyadzi, G.en
dc.contributor.authorMutuo, P.en
dc.contributor.authorPalm, C.A.en
dc.date.accessioned2023-10-13T14:02:04Zen
dc.date.available2023-10-13T14:02:04Zen
dc.identifier.urihttps://hdl.handle.net/10568/132252
dc.titleThe fate of nitrogen during agricultural intensification in East Africa: nitrogen budgets in contrasting agroecosystemsen
dcterms.abstractThe intensification of agricultural systems in sub-Saharan Africa (SSA) is necessary to reduce poverty and improve food security, but increased nutrient applications in smallholder systems could have negative consequences for water quality, greenhouse gas emissions, and air quality. We tracked nitrogen (N) inputs and measured maize (Zea mays) biomass, grain yields, N leaching, and nitric oxide (NO) and nitrous oxide fluxes from a clayey soil in Yala, Kenya and a sandy soil in Tumbi, Tanzania, with application rates of 0, 50, 75, 100, 150, and 200 kg N ha−1 yr−1 over two cropping seasons. Maize yields were 4.5 times higher in Yala than Tumbi, but yields plateaued at both sites with fertilizer applications at or above 100 kg N ha−1 yr−1. Partial N budgets in Yala were typically negative, meaning more N was exported in maize biomass plus grain or lost from the system than was added in fertilizer. In Tumbi, N budgets were negative at lower fertilizer levels but positive at higher fertilizer levels. At both sites most (96%) of the N was lost through maize biomass/grain removal and N leaching. Fertilizer additions at or less than 50 kg N ha−1 yr−1 on these two contrasting sites resulted in minor gaseous N losses, and fertilizer additions less than 200 kg N ha−1 yr−1 caused relatively little change to N leaching losses. This indicates that the modest increases in fertilizer use required to improve maize yields will not greatly increase cropland N losses. Plain Language Summary Crop yields in smallholder agriculture across sub-Saharan Africa are low but could be increased by greater applications of nitrogen fertilizer. However, greater use of nitrogen fertilizer creates potential for higher emissions of nitrogen trace gases and nitrogen leaching losses. This study added nitrogen fertilizer doses (0, 50, 75, 100, 150, and 200 kg of nitrogen per hectare) to maize cropland in two smallholder farming sites, one on clay-rich soils in Kenya and one on sandy soils in Tanzania. It tracked removal of nitrogen fertilizer via harvested maize and losses as nitrous oxide (a greenhouse gas), NO (an air pollutant), and leaching of soil solution. Yields were 4.5 times higher on the clayey soil; yields plateaued at nitrogen application above 100 kg per hectare. Leaching losses far exceeded gaseous losses at both sites: 96% of nitrogen was removed in harvested crops and soil solution. Nitrogen additions at or below 50 kg of nitrogen per hectare led to minor increases in gaseous nitrogen losses and additions less than 200 kg of nitrogen per hectare did not increase soil solution losses. This indicates that the modest increases in fertilizer use required to improve maize yields will not greatly increase cropland nitrogen losses.en
dcterms.accessRightsOpen Access
dcterms.audienceScientistsen
dcterms.available2023-07-09
dcterms.bibliographicCitationTully, K.L., Hickman, J.E., Russo, T.A., Neill, C., Matata, P., Nyadzi, G., ... & Palm, C.A. (2023). The fate of nitrogen during agricultural intensification in East Africa: nitrogen budgets in contrasting agroecosystems. Journal of Geophysical Research: Biogeosciences, 128(7): e2022JG007128, 1-22.en
dcterms.descriptionOpen Access Articleen
dcterms.extent1-22en
dcterms.issued2023
dcterms.languageen
dcterms.licenseCC-BY-4.0
dcterms.publisherAmerican Geophysical Unionen
dcterms.subjectagricultureen
dcterms.subjectintensificationen
dcterms.subjectsub-saharan africaen
dcterms.subjectfood securityen
dcterms.subjectsmallholdersen
dcterms.subjecteast africaen
dcterms.typeJournal Article

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