Soil fertility management in sub-Saharan Africa

Donovan, Graeme

doi:10.1596/0-8213-4236-3

Cited by 55 publications

(31 citation statements)

References 22 publications

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“…The nitrophilic nature of the maize crop was illustrated by a consistent response to N fertilizer, which almost doubled yields to 1.61-2.15 Mg ha −1 . This response is consistent with the literature (3,23), and the rationale for Malawi government subsidizes (Fig. S1).…”

Section: Discussionsupporting

confidence: 91%

“…This was assessed by calculating the value cost ratio (VCR) for each system, compared with the baseline system of unfertilized monoculture maize. This is a useful means to systematically compare disparate farming systems (23). The VCR was favorable (>3) for all systems at a maize grain/ fertilizer price ratio of 2:1, which was the prevalent ratio when the research was conducted.…”

Section: Resultsmentioning

confidence: 99%

“…The SP rotation system was an outstanding performer countrywide, with VCRs of 7.3-9.4 at historical prices and 4.8-5.1 at higher fertilizer prices. Although a VCR >2.0 is generally considered economically attractive to farmers, a VCR may need to be >4 to support technology adoption by risk-adverse, cash-poor farmers in a highly variable environment (23).…”

Section: Discussionmentioning

confidence: 99%

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Biodiversity can support a greener revolution in Africa

Snapp

Blackie

Gilbert

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

302

216

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The Asian green revolution trebled grain yields through agrochemical intensification of monocultures. Associated environmental costs have subsequently emerged. A rapidly changing world necessitates sustainability principles be developed to reinvent these technologies and test them at scale. The need is particularly urgent in Africa, where ecosystems are degrading and crop yields have stagnated. An unprecedented opportunity to reverse this trend is unfolding in Malawi, where a 90% subsidy has ensured access to fertilization and improved maize seed, with substantive gains in productivity for millions of farmers. To test if economic and ecological sustainability could be improved, we preformed manipulative experimentation with crop diversity in a countrywide trial (n = 991) and at adaptive, local scales through a decade of participatory research (n = 146). Spatial and temporal treatments compared monoculture maize with legume-diversified maize that included annual and semiperennial (SP) growth habits in temporal and spatial combinations, including rotation, SP rotation, intercrop, and SP intercrop systems. Modest fertilizer intensification doubled grain yield compared with monoculture maize. Biodiversity improved ecosystem function further: SP rotation systems at half-fertilizer rates produced equivalent quantities of grain, on a more stable basis (yield variability reduced from 22% to 13%) compared with monoculture. Across sites, profitability and farmer preference matched: SP rotations provided twofold superior returns, whereas diversification of maize with annual legumes provided more modest returns. In this study, we provide evidence that in Africa, crop diversification can be effective at a countrywide scale, and that shrubby, grain legumes can enhance environmental and food security.ecosystem services | nitrogen | rural development | sustainable agriculture

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Section: Discussionsupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Biodiversity can support a greener revolution in Africa

Snapp

Blackie

Gilbert

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

302

216

View full text Add to dashboard Cite

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“…Such intensification strategies should address sustainable soil management and farming techniques. Given the fact that aridity generally decreases the ease with which sustainable farming techniques can be developed (Øygard et al, 1999) and integrated nutrient management implemented (Donovan and Casey, 1998;Vanlauwe et al, 2002), an approach that combines organic and mineral methods of soil …”

Section: Factors Affecting Land-use Changementioning

confidence: 99%

Seasonal migration and land‐use change in Ghana

Braimoh

2004

Land Degrad Dev

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When farmers migrate yearly to a village to carry out intense farming during the rainy season, and thereafter return to a more permanent place of abode this is referred to as seasonal migration. The impact of such migration on land-use/land-cover change in an area within the Volta Basin of Ghana was examined using satellite image analysis and socioeconomic surveys. The most drastic land-cover change involved the conversion of woodland to agricultural land, while there was also a general transition to less vegetation cover. Socioeconomic surveys revealed that most of the migration occurred during the post-structural adjustment period in Ghana with declining soil fertility accounting for the highest per cent of causes of migration. Multiple regression results highlighted the role of population size and distribution, marketing of agricultural produce and technological evolution of the household in determining agricultural land-use change. Policy initiatives that could lead to environment conservation are suggested.

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“…Both P and N deficiencies are widespread in sub-Saharan African agricultural soils and are the main causes of low crop productivity, especially in smallholder agriculture Sanchez et al, 1997;Haileslassie et al, 2006). Under these conditions, crop production relies on SOM decomposition and mineral weathering as sources of plant nutrients (Donovan & Casey, 1998;Sanchez & Swaminathan, 2005). Although the importance of fertilizer in the tropics has been recognized, its use is low (FAO, 2003).…”

Section: Introductionmentioning

confidence: 99%

Nutrient constraints to tropical agroecosystem productivity in long‐term degrading soils

Ngoze

Riha

Lehmann

et al. 2008

Global Change Biology

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Soil degradation is one of the most serious threats to sustainable crop production in many tropical agroecosystems where extensification rather than intensification of agriculture has occurred. In the highlands of western Kenya, we investigated soil nitrogen (N) and phosphorus (P) constraints to maize productivity across a cultivation chronosequence in which land-use history ranged from recent conversion from primary forest to 100 years in continuous cropping. Nutrient treatments included a range of N and P fertilizer rates applied separately and in combination. Maize productivity without fertilizer was used as a proxy measure for indigenous soil fertility (ISF). Soil pools of mineral nitrogen, strongly bound P and plant-available P decreased by 82%, 31% and 36%, and P adsorption capacity increased by 51% after 100 years of continuous cultivation. For the long rainy season (LR), grain yield without fertilizer declined rapidly as cultivation age increased from 0 to 25 years and then gradually declined to a yield of 1.6 Mg ha À1 , which was maintained as time under cultivation increased from 60 to 100 years. LR grain yield in the old conversions was only 24% of the average young conversion grain yield (6.4 Mg ha À1 ). Application of either N or P alone significantly increased grain yield in both the LR and short rainy (SR) seasons, but only application of 120 kg N ha À1 on the old conversion increased yield by 41 Mg ha À1 . In both SR and LR, there was a greater average yield increment response to N and P when applied together (ranging from 1 to 3.8 Mg ha À1 for the LR), with the greatest responses on the old conversions. The benefit-cost ratio (BCR) for applying 120 kg N ha À1 alone was o1 except on the old conversions, while BCRs were41 for applying 25 kg P ha À1 alone at all levels of conversion for both seasons. Application of both N (120 kg N ha À1 ) and P (25 kg P ha À1 ) on the old conversions resulted in the greatest BCRs. This study clearly indicates that maize productivity responses to N and P fertilizer are significantly affected by the age of cultivation and its influence on ISF, but that loss of productivity can be restored rapidly when these limiting nutrients are applied. Management strategies should consider ISF and economic factors to determine optimal N and P input requirements for achieving and sustaining profitable crop production on degraded soils.

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Soil fertility management in sub-Saharan Africa

Cited by 55 publications

References 22 publications

Biodiversity can support a greener revolution in Africa

Biodiversity can support a greener revolution in Africa

Seasonal migration and land‐use change in Ghana

Nutrient constraints to tropical agroecosystem productivity in long‐term degrading soils

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