Paper · 2019 · Environmental Research Letters

Evidence map of crop diversification strategies at the global scale

Damien Beillouin; Tamara Ben-Ari; David Makowski

11
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173
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Open access · cc-by

Abstract

Abstract The diversification of cropping systems encompasses different strategies that may help maintain or enhance the sustainability of agriculture. Thousands of experiments have been carried out around the world since almost five decades to evaluate and compare the performances of various diversification strategies in a wide array of agroecosystems and climates. Although these analyses have been synthesized in a growing number of meta-analyses, the information remains somewhat fragmented. A multicriteria systematic synthesis of worldwide agricultural diversification is still lacking. Here, we review all meta-analyses conducted on crop diversification strategies and produce a detailed overview of their results and of their quality. We identified and analyzed 99 meta-analyses summarizing the results of more than 3700 agronomic experiments on seven crop diversification strategies. Among these strategies, rotation and associated plant species are dominant in the literature followed by intercropping, agroforestry and landscape heterogeneity. Our analysis reveals that rotation and intercropping are associated with yield increases. Agroforestry systematically induces an improvement of biodiversity and soil quality—in particular soil organic carbon. We show that, regardless of the context, a combination of several diversification strategies outperforms any individual strategy. Our review reveals that a significant knowledge gap remains, in particular regarding water use, farmers’ profitability, product quality and production stability. Few meta-analyses investigate the performance of landscape heterogeneity and of systems with species other than cereals and pulses. Additionally, we show that most of the meta-analyses studied cannot be considered fully transparent and reproducible. Their conclusions should therefore be interpreted with caution. Our systematic mapping provides a benchmark to guide and improve the relevance and reliability of future meta-analyses in agronomy.

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Claims 11

Method / resourceobservedoriginal resultmeasured

Claim · model-written summary

The review identified 99 meta analyses covering over 3700 agronomic experiments.

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cropt0
Outcome
meta-analysese0
Value
99e0

Verbatim

e0

“We identified and analyzed 99 meta-analyses summarizing the results of more than 3700 agronomic experiments”

✓ located verbatim in the source · abstract, characters 744–851 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Observationobservedoriginal resultmeasured

Claim · model-written summary

Rotation and associated plant species dominate the diversification literature.

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cropt0
Outcome
dominant in the literaturee0

Verbatim

e0

“rotation and associated plant species are dominant in the literature followed by intercropping, agroforestry and landscape heterogeneity”

✓ located verbatim in the source · abstract, characters 918–1054 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Associationobservedoriginal resultpositivemeasured

Claim · model-written summary

Rotation is associated with increased yield.

Taxon
cropt0
Treatment
rotatione0
Outcome
yielde0
Direction
increasese0

Verbatim

e0

“rotation and intercropping are associated with yield increases”

✓ located verbatim in the source · abstract, characters 1082–1144 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Associationobservedoriginal resultpositivemeasured

Claim · model-written summary

Intercropping is associated with increased yield.

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cropt0
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intercroppinge0
Outcome
yielde0
Direction
increasese0

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e0

“rotation and intercropping are associated with yield increases”

✓ located verbatim in the source · abstract, characters 1082–1144 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Associationobservedoriginal resultpositivemeasured

Claim · model-written summary

Agroforestry improves biodiversity.

Taxon
cropt0
Treatment
Agroforestrye0
Outcome
biodiversitye0
Direction
improvemente0

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e0

“Agroforestry systematically induces an improvement of biodiversity and soil quality—in particular soil organic carbon”

✓ located verbatim in the source · abstract, characters 1146–1263 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Associationobservedoriginal resultpositivemeasured

Claim · model-written summary

Agroforestry improves soil quality and organic carbon.

Taxon
cropt0
Treatment
Agroforestrye0
Outcome
soil quality—in particular soil organic carbone0
Direction
improvemente0

Verbatim

e0

“Agroforestry systematically induces an improvement of biodiversity and soil quality—in particular soil organic carbon”

✓ located verbatim in the source · abstract, characters 1146–1263 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Associationobservedoriginal resultpositivemeasured

Claim · model-written summary

Combining diversification strategies outperforms any individual strategy.

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cropt0
Treatment
a combination of several diversification strategiese0
Outcome
outperformse0
Direction
outperformse0
Comparator
any individual strategye0

Verbatim

e0

“regardless of the context, a combination of several diversification strategies outperforms any individual strategy”

✓ located verbatim in the source · abstract, characters 1279–1393 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Observationobservedoriginal resultnegativemeasured

Claim · model-written summary

The review found knowledge gaps in water use, profitability, quality and stability.

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cropt0
Outcome
knowledge gape0

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e0

“a significant knowledge gap remains, in particular regarding water use, farmers’ profitability, product quality and production stability”

✓ located verbatim in the source · abstract, characters 1419–1555 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Observationobservedoriginal resultnegativemeasured

Claim · model-written summary

Few meta analyses addressed landscape heterogeneity or species beyond cereals and pulses.

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cropt0
Outcome
Few meta-analyses investigate the performancee0

Verbatim

e0

“Few meta-analyses investigate the performance of landscape heterogeneity and of systems with species other than cereals and pulses”

✓ located verbatim in the source · abstract, characters 1557–1687 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Observationobservedoriginal resultnegativemeasured

Claim · model-written summary

Most meta analyses were not fully transparent or reproducible.

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cropt0
Outcome
cannot be considered fully transparent and reproduciblee0

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e0

“most of the meta-analyses studied cannot be considered fully transparent and reproducible”

✓ located verbatim in the source · abstract, characters 1716–1805 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑
Recommendationauthor interpretationoriginal resultbasis n/a

Claim · model-written summary

Authors recommend caution in interpreting the meta analyses conclusions.

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cropt0
Outcome
interpreted with cautione0

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e0

“Their conclusions should therefore be interpreted with caution”

✓ located verbatim in the source · abstract, characters 1807–1869 · show in text ↑
t0

“crop”

✓ located verbatim in the source · title, characters 16–20 · show in text ↑