Abstract
SUMMARY In the Central Rift Valley (CRV) of Ethiopia, low productive cereal systems and a declining resource base call for options to increase crop productivity and improve resource use efficiency to meet the growing demand of food. We compiled and analysed a large amount of data from farmers’ fields (>10,000) and experimental data across the CRV from 2004–2009 to quantify yield gaps ( Y g ) between actual (average and best performing farmers) and experimental (water-limited potential ( Y w )) yields of maize and wheat in homogenous farming zones (HFZs). Resource use efficiencies (nutrients and water) of maize and wheat were also analysed to assess spatial variation and scope for improvements. The average (2004–2009) yield gap of maize and wheat in the CRV ranged between 4.2 t ha −1 and 9.2 t ha −1 , and 2.5 t ha −1 and 4.7 t ha −1 , respectively, across farming zones. The yield gap was lowest in the Central lowlands, where Y w was also lowest, i.e. 6.5 t ha −1 for maize and 4.4 t ha −1 for wheat, compared with Y w in the Eastern highlands (11 t ha −1 for maize and 6.7 t ha −1 for wheat) and Western highlands (10.8 t ha −1 for maize and 5.7 t ha −1 for wheat). The actual nitrogen (N) and phosphorus (P) application in farmers’ fields was low, as about 46% of maize and 27% of wheat fields did not receive fertilizers, while the average applied mineral fertilizer rates across all farmers (2.6–16.5 kg N ha −1 and 2.2–17.3 kg P ha −1 across HFZs and crops) were far below the recommended rate. On average, the best performing farmers applied 8–20 kg N ha −1 and 5–21 kg P ha −1 ranging across HFZs and crops. Increasing N application to recommended rates had only a small effect on narrowing the yield gap under current farmers’ management. Therefore, the yield gap closure strongly depends on improving other aspects of crop management while paying attention to the interaction with nutrient management. Since rain water use efficiency (seasonal rainfall) of water-limited yields was 12–17.3 kg mm −1 for maize and 7.4–10.6 kg mm −1 for wheat and much higher than that of actual yields (2.7–4.3 kg mm −1 for maize and 2.3–3.5 kg mm −1 for wheat), improving the input use and crop management can increase water use efficiency. A large set of experimental and survey data enabled us to gain insight in the spatial and temporal variation in yield gaps and input rates and in differences between average and the best performing farmers.
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Claims 16
Claim · model-written summary
Maize yield gaps ranged from 4.2 to 9.2 t ha −1 across farming zones.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The average (2004–2009) yield gap of maize and wheat in the CRV ranged between 4.2 t ha −1 and 9.2 t ha −1 , and 2.5 t ha −1 and 4.7 t ha −1 , respectively, across farming zones.”
Claim · model-written summary
Wheat yield gaps ranged from 2.5 to 4.7 t ha −1 across farming zones.
- Taxon
- wheat
Triticum aestivume0 - Outcome
- yield gape0
- Value
- 2.5 t ha −1 and 4.7 t ha −1e0
- Setting
- CRVe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The average (2004–2009) yield gap of maize and wheat in the CRV ranged between 4.2 t ha −1 and 9.2 t ha −1 , and 2.5 t ha −1 and 4.7 t ha −1 , respectively, across farming zones.”
Claim · model-written summary
Yield gaps and water-limited potential yields were lowest in the Central lowlands for both crops.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The yield gap was lowest in the Central lowlands, where Y w was also lowest, i.e. 6.5 t ha −1 for maize and 4.4 t ha −1 for wheat”
Claim · model-written summary
Maize water-limited yield was 6.5 t ha −1 in Central lowlands, 11 t ha −1 in Eastern highlands, and 10.8 t ha −1 in Western highlands.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“6.5 t ha −1 for maize and 4.4 t ha −1 for wheat, compared with Y w in the Eastern highlands (11 t ha −1 for maize and 6.7 t ha −1 for wheat) and Western highlands (10.8 t ha −1 for maize and 5.7 t ha −1 for wheat)”
e1“The yield gap was lowest in the Central lowlands, where Y w was also lowest, i.e. 6.5 t ha −1 for maize and 4.4 t ha −1 for wheat”
Claim · model-written summary
Wheat water-limited yield was 4.4 t ha −1 in Central lowlands.
- Taxon
- wheatTriticum aestivume0
- Outcome
- Y we0
- Value
- 4.4 t ha −1e0
- Setting
- Central lowlandse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The yield gap was lowest in the Central lowlands, where Y w was also lowest, i.e. 6.5 t ha −1 for maize and 4.4 t ha −1 for wheat”
Claim · model-written summary
About 46% of maize fields received no fertilizer.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“about 46% of maize and 27% of wheat fields did not receive fertilizers”
Claim · model-written summary
About 27% of wheat fields received no fertilizer.
- Taxon
- wheatTriticum aestivume0
- Outcome
- did not receive fertilizerse0
- Value
- 27%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“about 46% of maize and 27% of wheat fields did not receive fertilizers”
Claim · model-written summary
Average mineral nitrogen fertilizer rates were 2.6–16.5 kg N ha −1, below recommendations.
- Outcome
- average applied mineral fertilizer ratese0
- Direction
- far belowe0
- Value
- 2.6–16.5 kg N ha −1e0
- Comparator
- recommended ratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“average applied mineral fertilizer rates across all farmers (2.6–16.5 kg N ha −1 and 2.2–17.3 kg P ha −1 across HFZs and crops) were far below the recommended rate”
e1“The average (2004–2009) yield gap of maize and wheat in the CRV ranged between 4.2 t ha −1 and 9.2 t ha −1 , and 2.5 t ha −1 and 4.7 t ha −1 , respectively, across farming zones.”
Claim · model-written summary
Average mineral phosphorus fertilizer rates were 2.2–17.3 kg P ha −1, below recommendations.
- Taxon
- wheatTriticum aestivume1
- Outcome
- average applied mineral fertilizer ratese0
- Direction
- far belowe0
- Value
- 2.2–17.3 kg P ha −1e0
- Comparator
- recommended ratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“average applied mineral fertilizer rates across all farmers (2.6–16.5 kg N ha −1 and 2.2–17.3 kg P ha −1 across HFZs and crops) were far below the recommended rate”
e1“Resource use efficiencies (nutrients and water) of maize and wheat were also analysed”
Claim · model-written summary
Best-performing farmers applied 8–20 kg N ha −1.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the best performing farmers applied 8–20 kg N ha −1 and 5–21 kg P ha −1 ranging across HFZs and crops”
e1“Resource use efficiencies (nutrients and water) of maize and wheat were also analysed”
Claim · model-written summary
Best-performing farmers applied 5–21 kg P ha −1.
- Taxon
- wheatTriticum aestivume1
- Outcome
- appliede0
- Value
- 5–21 kg P ha −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the best performing farmers applied 8–20 kg N ha −1 and 5–21 kg P ha −1 ranging across HFZs and crops”
e1“Resource use efficiencies (nutrients and water) of maize and wheat were also analysed”
Claim · model-written summary
Increasing nitrogen application to recommended rates only slightly narrowed yield gaps under current farmer management.
- Treatment
- Increasing N application to recommended ratese0
- Outcome
- yield gape0
- Direction
- narrowinge0
- Qualifier
- only a small effecte0
- Comparator
- current farmers’ managemente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increasing N application to recommended rates had only a small effect on narrowing the yield gap under current farmers’ management.”
e1“Resource use efficiencies (nutrients and water) of maize and wheat were also analysed”
Claim · model-written summary
Water-limited maize rainwater use efficiency was 12–17.3 kg mm −1 versus actual-yield efficiency of 2.7–4.3 kg mm −1.
- Outcome
- rain water use efficiencye0
- Direction
- much highere0
- Value
- 12–17.3 kg mm −1e0
- Qualifier
- 2.7–4.3 kg mm −1e0
- Comparator
- actual yieldse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rain water use efficiency (seasonal rainfall) of water-limited yields was 12–17.3 kg mm −1 for maize and 7.4–10.6 kg mm −1 for wheat and much higher than that of actual yields (2.7–4.3 kg mm −1 for maize and 2.3–3.5 kg mm −1 for wheat)”
Claim · model-written summary
Water-limited wheat rainwater use efficiency was 7.4–10.6 kg mm −1 versus actual-yield efficiency of 2.3–3.5 kg mm −1.
- Taxon
- wheatTriticum aestivume0
- Outcome
- rain water use efficiencye0
- Direction
- much highere0
- Value
- 7.4–10.6 kg mm −1e0
- Qualifier
- 2.3–3.5 kg mm −1e0
- Comparator
- actual yieldse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rain water use efficiency (seasonal rainfall) of water-limited yields was 12–17.3 kg mm −1 for maize and 7.4–10.6 kg mm −1 for wheat and much higher than that of actual yields (2.7–4.3 kg mm −1 for maize and 2.3–3.5 kg mm −1 for wheat)”
Claim · model-written summary
Closing yield gaps depends strongly on improving crop management together with nutrient management.
- Outcome
- improving other aspects of crop managemente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yield gap closure strongly depends on improving other aspects of crop management while paying attention to the interaction with nutrient management.”
e1“Resource use efficiencies (nutrients and water) of maize and wheat were also analysed”
Claim · model-written summary
Improved input use and crop management can increase water use efficiency.
- Taxon
- wheatTriticum aestivume1
- Outcome
- increase water use efficiencye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“improving the input use and crop management can increase water use efficiency.”
e1“Resource use efficiencies (nutrients and water) of maize and wheat were also analysed”
The same questions in other papers
nitrogen · yield · Zea mays (maize)Positive and negative results
1,905 papers in the same direction as this paper · 234 in the opposite direction · 45 reporting no difference from an alternative
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- negative
- no effect
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