title: Affordable nutrient solutions for improved food security as evidenced by crop trials.
abstract: The continuing depletion of nutrients from agricultural soils in Sub-Saharan African is accompanied by a lack of substantial progress in crop yield improvement. In this paper we investigate yield gaps for corn under two scenarios: a micro-dosing scenario with marginal increases in nitrogen (N) and phosphorus (P) of 10 kg ha(-1) and a larger yet still conservative scenario with proposed N and P applications of 80 and 20 kg ha(-1) respectively. The yield gaps are calculated from a database of historical FAO crop fertilizer trials at 1358 locations for Sub-Saharan Africa and South America. Our approach allows connecting experimental field scale data with continental policy recommendations. Two critical findings emerged from the analysis. The first is the degree to which P limits increases in corn yields. For example, under a micro-dosing scenario, in Africa, the addition of small amounts of N alone resulted in mean yield increases of 8% while the addition of only P increased mean yields by 26%, with implications for designing better balanced fertilizer distribution schemes. The second finding was the relatively large amount of yield increase possible for a small, yet affordable amount of fertilizer application. Using African and South American fertilizer prices we show that the level of investment needed to achieve these results is considerably less than 1% of Agricultural GDP for both a micro-dosing scenario and for the scenario involving higher yet still conservative fertilizer application rates. In the latter scenario realistic mean yield increases ranged between 28 to 85% in South America and 71 to 190% in Africa (mean plus one standard deviation). External investment in this low technology solution has the potential to kick start development and could complement other interventions such as better crop varieties and improved economic instruments to support farmers.
authors.affiliation: International Institute for Applied Systems Analysis (IIASA), Ecosystem Services and Management Program, Laxenburg, Austria. velde@iiasa.ac.at
authors.forename: Marijn
authors.initials: M
authors.lastname: van der Velde
authors.forename: Linda
authors.initials: L
authors.lastname: See
authors.forename: Liangzhi
authors.initials: L
authors.lastname: You
authors.forename: Juraj
authors.initials: J
authors.lastname: Balkovič
authors.forename: Steffen
authors.initials: S
authors.lastname: Fritz
authors.forename: Nikolay
authors.initials: N
authors.lastname: Khabarov
authors.forename: Michael
authors.initials: M
authors.lastname: Obersteiner
authors.forename: Stanley
authors.initials: S
authors.lastname: Wood
mesh_terms: D017954:Africa South of the Sahara; D000383:Agriculture / Q000191:economics; D018556:Crops, Agricultural; D005308:Fertilizers; D005523:Food Supply / Q000191:economics; D005843:Geography; D008962:Models, Theoretical; D009584:Nitrogen; D010758:Phosphorus; D012987:Soil / Q000737:chemistry*; D012996:Solutions; D013020:South America; D003313:Zea mays / Q000254:growth & development
chemical_list: D005308:Fertilizers; D012987:Soil; D012996:Solutions; D010758:Phosphorus; D009584:Nitrogen
references.citation: Science. 2009 Aug 7;325(5941):680-1
references.pmid: 19661405
references.citation: Science. 2002 Mar 15;295(5562):2019-20
references.pmid: 11896257
references.citation: Nature. 2012 Apr 18;484(7394):318
references.pmid: 22517154
references.citation: Nature. 2012 Oct 11;490(7419):254-7
references.pmid: 22932270
references.citation: Science. 2003 Dec 12;302(5652):1917-9
references.pmid: 14671289
references.citation: Science. 2010 Feb 12;327(5967):831-2
references.pmid: 20150493
references.citation: Proc Natl Acad Sci U S A. 2012 Apr 17;109(16):6348-53
references.pmid: 22431593
references.citation: Nature. 2012 Mar 28;483(7391):525-7
references.pmid: 22460878
references.citation: Chemosphere. 2011 Aug;84(6):779-84
references.pmid: 21481910
references.citation: Nature. 2011 Oct 12;478(7369):337-42
references.pmid: 21993620
references.citation: Science. 2010 Feb 12;327(5967):812-8
references.pmid: 20110467