Closing maize yield gaps in sub-Saharan Africa will boost soil N2O emissions

AbstractIn sub-Saharan Africa (SSA), precipitation is an important driver of agricultural production. In Uganda, maize production is essentially rain-fed. However, due to changes in climate, projected maize yield targets have not often been met as actual observed maize yields are often below simulated/projected yields. This outcome has often been attributed to parallel gaps in precipitation. This study aims at identifying maize yield and precipitation gaps in Uganda for the period 1998–2017. Time series historical actual observed maize yield data (hg/ha/year) for the period 1998–2017 were collected from FAOSTAT. Actual observed maize growing season precipitation data were also collected from the climate portal of World Bank Group for the period 1998–2017. The simulated or projected maize yield data and the simulated or projected growing season precipitation data were simulated using a simple linear regression approach. The actual maize yield and actual growing season precipitation data were now compared with the simulated maize yield data and simulated growing season precipitation to establish the yield gaps. The results show that three key periods of maize yield gaps were observed (period one: 1998, period two: 2004–2007 and period three: 2015–2017) with parallel precipitation gaps. However, in the entire series (1998–2017), the years 2008–2009 had no yield gaps yet, precipitation gaps were observed. This implies that precipitation is not the only driver of maize yields in Uganda. In fact, this is supported by a low correlation between precipitation gaps and maize yield gaps of about 6.3%. For a better understanding of cropping systems in SSA, other potential drivers of maize yield gaps in Uganda such as soils, farm inputs, crop pests and diseases, high yielding varieties, literacy, and poverty levels should be considered.

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Beyond fertilizer for closing yield gaps in sub-Saharan Africa

Nature Food ◽

10.1038/s43016-021-00386-7 ◽

2021 ◽

Author(s):

André F. Van Rooyen ◽

Henning Bjornlund ◽

Jamie Pittock

Keyword(s):

Sub Saharan Africa ◽

Yield Gaps ◽

Sub Saharan

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Temperature, maize yield, and civil conflicts in sub-Saharan Africa

Climatic Change ◽

10.1007/s10584-017-1941-0 ◽

2017 ◽

Vol 142 (1-2) ◽

pp. 183-197 ◽

Cited By ~ 6

Author(s):

Tackseung Jun

Keyword(s):

Maize Yield ◽

Sub Saharan Africa ◽

Civil Conflicts ◽

Sub Saharan

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Unravelling the variability and causes of smallholder maize yield gaps in Ethiopia

Food Security ◽

10.1007/s12571-019-00981-4 ◽

2019 ◽

Vol 12 (1) ◽

pp. 83-103 ◽

Cited By ~ 4

Author(s):

Banchayehu Tessema Assefa ◽

Jordan Chamberlin ◽

Pytrik Reidsma ◽

João Vasco Silva ◽

Martin K. van Ittersum

Keyword(s):

Stochastic Frontier Analysis ◽

National Level ◽

Total Yield ◽

Maize Yield ◽

Sub Saharan Africa ◽

Yield Gap ◽

Potential Yield ◽

Frontier Analysis ◽

Yield Gaps ◽

Maize Yields

AbstractEthiopia has achieved the second highest maize yield in sub-Saharan Africa. Yet, farmers’ maize yields are still much lower than on-farm and on-station trial yields, and only ca. 20% of the estimated water-limited potential yield. This article provides a comprehensive national level analysis of the drivers of maize yields in Ethiopia, by decomposing yield gaps into efficiency, resource and technology components, and accounting for a broad set of detailed input and crop management choices. Stochastic frontier analysis was combined with concepts of production ecology to estimate and explain technically efficient yields, the efficiency yield gap and the resource yield gap. The technology yield gap was estimated based on water-limited potential yields from the Global Yield Gap Atlas. The relative magnitudes of the efficiency, resource and technology yield gaps differed across farming systems; they ranged from 15% (1.6 t/ha) to 21% (1.9 t/ha), 12% (1.3 t/ha) to 25% (2.3 t/ha) and 54% (4.8 t/ha) to 73% (7.8 t/ha), respectively. Factors that reduce the efficiency yield gap include: income from non-farm sources, value of productive assets, education and plot distance from home. The resource yield gap can be explained by sub-optimal input use, from a yield perspective. The technology yield gap comprised the largest share of the total yield gap, partly due to limited use of fertilizer and improved seeds. We conclude that targeted but integrated policy design and implementation is required to narrow the overall maize yield gap and improve food security.

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Modeling maize yield responses to improvement in nutrient, water and cultivar inputs in sub-Saharan Africa

Agricultural Systems ◽

10.1016/j.agsy.2013.04.002 ◽

2013 ◽

Vol 119 ◽

pp. 22-34 ◽

Cited By ~ 43

Author(s):

Christian Folberth ◽

Hong Yang ◽

Thomas Gaiser ◽

Karim C. Abbaspour ◽

Rainer Schulin

Keyword(s):

Maize Yield ◽

Sub Saharan Africa ◽

Sub Saharan ◽

Yield Responses

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Nitrous Oxide Emissions from Smallholders’ Cropping Systems in Sub-Saharan Africa

Advances in Agriculture ◽

10.1155/2021/4800527 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Shaankua E. Lemarpe ◽

Collins M. Musafiri ◽

Joseph M. Macharia ◽

Milka N. Kiboi ◽

Onesmus K. Ng’etich ◽

...

Keyword(s):

Climate Change ◽

Management Practices ◽

Cropping Systems ◽

Empirical Studies ◽

Sub Saharan Africa ◽

N2o Emissions ◽

Ozone Layer Depletion ◽

Site Specific ◽

Emissions Mitigation ◽

Sub Saharan

Increased concentration of atmospheric nitrous oxide (N2O), a potent greenhouse gas (GHG), is of great concern due to its impact on ozone layer depletion leading to climate change. Ozone layer depletion allows penetration of ultraviolet radiations, which are hazardous to human health. Climate change culminates in reduced food productivity. Limited empirical studies have been conducted in Sub-Saharan Africa (SSA) to quantify and understand the dynamics of soil N2O fluxes from smallholder cropping systems. The available literature on soil N2O fluxes in SSA is limited; hence, there is a pressing need to consolidate it to ease mitigation targeting and policy formulation initiatives. We reviewed the state of N2O emissions from selected cropping systems, drivers that significantly influence N2O emissions, and probable soil N2O emissions mitigation options from 30 studies in SSA cropping systems have been elucidated here. The review outcome indicates that coffee, tea, maize, and vegetables emit N2O ranging from 1 to 1.9, 0.4 to 3.9, 0.1 to 4.26, and 48 to 113.4 kg N2O-N ha-1 yr−1, respectively. The yield-scaled and N2O emissions factors ranged between 0.08 and 67 g N2O-N kg−1 and 0.01 and 4.1%, respectively, across cropping systems. Soil characteristics, farm management practices, and climatic and environmental conditions were significant drivers influencing N2O emissions across SSA cropping systems. We found that site-specific soil N2O emissions mitigation measures are required due to high variations in N2O drivers across SSA. We conclude that appropriate fertilizer and organic input management combined with improved soil management practices are potential approaches in N2O emissions mitigation in SSA. We recommend that (i) while formulating soil N2O emissions mitigation approaches, in SSA, policymakers should consider site-specific targeting approaches, and (ii) more empirical studies need to be conducted in diverse agroecological zones of SSA to qualify various mitigation options on N2O emissions, yield-scaled N2O emissions, and N2O emission factors which are essential in improving national and regional GHG inventories.

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Effect of legume intercropping on N<sub>2</sub>O emissions and CH<sub>4</sub> uptake during maize production in the Great Rift Valley, Ethiopia

Biogeosciences ◽

10.5194/bg-17-345-2020 ◽

2020 ◽

Vol 17 (2) ◽

pp. 345-359

Author(s):

Shimelis Gizachew Raji ◽

Peter Dörsch

Keyword(s):

Rift Valley ◽

Crop Production ◽

Growing Season ◽

Maize Yield ◽

Sub Saharan Africa ◽

Ethiopian Rift ◽

N2o Emissions ◽

Mineral N ◽

Total N ◽

N Input

Abstract. Intercropping with legumes is an important component of climate-smart agriculture (CSA) in sub-Saharan Africa, but little is known about its effect on soil greenhouse gas (GHG) exchange. A field experiment was established at Hawassa in the Ethiopian rift valley, comparing nitrous oxide (N2O) and methane (CH4) fluxes in minerally fertilized maize (64 kg N ha−1) with and without Crotalaria (C. juncea) or lablab (L. purpureus) as intercrops over two growing seasons. To study the effect of intercropping time, intercrops were sown either 3 or 6 weeks after maize. The legumes were harvested at flowering, and half of the aboveground biomass was mulched. In the first season, cumulative N2O emissions were largest in 3-week lablab, with all other treatments being equal to or lower than the fertilized maize mono-crop. After reducing mineral N input to intercropped systems by 50 % in the second season, N2O emissions were comparable with the fully fertilized control. Maize-yield-scaled N2O emissions in the first season increased linearly with aboveground legume N yield (p=0.01), but not in the second season when early rains resulted in less legume biomass because of shading by maize. Growing-season N2O-N emission factors varied from 0.02 % to 0.25 % in 2015 and 0.11 % to 0.20 % in 2016 of the estimated total N input. Growing-season CH4 uptake ranged from 1.0 to 1.5 kg CH4-C ha−1, with no significant differences between treatments or years but setting off the N2O-associated emissions by up to 69 %. Our results suggest that leguminous intercrops may increase N2O emissions when developing large biomass in dry years but, when mulched, can replace part of the fertilizer N in normal years, thus supporting CSA goals while intensifying crop production in the region.

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Smallholder farms in eastern African tropical highlands have low soil greenhouse gas fluxes

Biogeosciences ◽

10.5194/bg-14-187-2017 ◽

2017 ◽

Vol 14 (1) ◽

pp. 187-202 ◽

Cited By ~ 18

Author(s):

David Pelster ◽

Mariana Rufino ◽

Todd Rosenstock ◽

Joash Mango ◽

Gustavo Saiz ◽

...

Keyword(s):

Greenhouse Gas ◽

Crop Production ◽

Crop Yields ◽

N Uptake ◽

Sub Saharan Africa ◽

N2o Emissions ◽

Vegetation Types ◽

Smallholder Farms ◽

Sub Saharan ◽

Ch4 And N2o

Abstract. Few field studies examine greenhouse gas (GHG) emissions from African agricultural systems, resulting in high uncertainty for national inventories. This lack of data is particularly noticeable in smallholder farms in sub-Saharan Africa, where low inputs are often correlated with low yields, often resulting in food insecurity as well. We provide the most comprehensive study in Africa to date, examining annual soil CO2, CH4 and N2O emissions from 59 smallholder plots across different vegetation types, field types and land classes in western Kenya. The study area consists of a lowland area (approximately 1200 m a.s.l.) rising approximately 600 m to a highland plateau. Cumulative annual fluxes ranged from 2.8 to 15.0 Mg CO2-C ha−1, −6.0 to 2.4 kg CH4-C ha−1 and −0.1 to 1.8 kg N2O-N ha−1. Management intensity of the plots did not result in differences in annual GHG fluxes measured (P = 0.46, 0.14 and 0.67 for CO2, CH4 and N2O respectively). The similar emissions were likely related to low fertilizer input rates (≤ 20 kg N ha−1). Grazing plots had the highest CO2 fluxes (P = 0.005), treed plots (plantations) were a larger CH4 sink than grazing plots (P = 0.05), while soil N2O emissions were similar across vegetation types (P = 0.59). This study is likely representative for low fertilizer input, smallholder systems across sub-Saharan Africa, providing critical data for estimating regional or continental GHG inventories. Low crop yields, likely due to low fertilization inputs, resulted in high (up to 67 g N2O-N kg−1 aboveground N uptake) yield-scaled emissions. Improvement of crop production through better water and nutrient management might therefore be an important tool in increasing food security in the region while reducing the climate footprint per unit of food produced.

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Forecasting the global extent of invasion of the cereal pest Spodoptera frugiperda, the fall armyworm

NeoBiota ◽

10.3897/neobiota.40.28165 ◽

2018 ◽

Vol 40 ◽

pp. 25-50 ◽

Cited By ~ 54

Author(s):

Regan Early ◽

Pablo González-Moreno ◽

Sean T. Murphy ◽

Roger Day

Keyword(s):

Fall Armyworm ◽

Maize Yield ◽

Sub Saharan Africa ◽

Potential Range ◽

Wet Season ◽

Distribution Models ◽

Climate Conditions ◽

Temperature And Precipitation ◽

Sub Saharan ◽

Transportation Routes

Fall armyworm, Spodopterafrugiperda, is a crop pest native to the Americas, which has invaded and spread throughout sub-Saharan Africa within two years. Recent estimates of 20–50% maize yield loss in Africa suggest severe impact on livelihoods. Fall armyworm is still infilling its potential range in Africa and could spread to other continents. In order to understand fall armyworm’s year-round, global, potential distribution, we used evidence of the effects of temperature and precipitation on fall armyworm life-history, combined with data on native and African distributions to construct Species Distribution Models (SDMs). We also investigated the strength of trade and transportation pathways that could carry fall armyworm beyond Africa. Up till now, fall armyworm has only invaded areas that have a climate similar to the native distribution, validating the use of climatic SDMs. The strongest climatic limits on fall armyworm’s year-round distribution are the coldest annual temperature and the amount of rain in the wet season. Much of sub-Saharan Africa can host year-round fall armyworm populations, but the likelihoods of colonising North Africa and seasonal migrations into Europe are hard to predict. South and Southeast Asia and Australia have climate conditions that would permit fall armyworm to invade. Current trade and transportation routes reveal Australia, China, India, Indonesia, Malaysia, Philippines and Thailand face high threat of fall armyworm invasions originating from Africa.

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