Abstract
Abstract Cereal–legume intercropping is promoted within semi‐arid regions as an adaptation strategy to water scarcity and drought for low‐input systems. Our objectives were firstly to evaluate the crop model APSIM for pearl millet ( Pennisetum glaucum (L.))—cowpea ( Vigna unguiculata (L.) Walp) intercropping—and secondly to investigate the hypothesis that intercropping provides complimentary yield under drought conditions. The APSIM model was evaluated against data from a two year on station field experiment during the dry season of a semi‐arid environment in Patancheru, India, with severe, partial and no water deficit stress (well‐watered); densities of 17 and 33 plants per m −2 , and intercrop and sole crop production of pearl millet and cowpea. Overall, APSIM captured the dynamics of grain yields, indicated by the Willmott Index of Agreement (IA: 1 optimal, 0 the worst) 0.91 from 36 data points (n), total biomass (IA: 0.90, n = 144), leaf area index (LAI, IA = 0.77, n = 66), plant height (IA 0.96, n = 104 pearl millet) and cowpea (IA 0.81, n = 102), as well as soil water (IA 0.73, n = 126). Model accuracy was reasonable in absolute terms (RMSE pearl millet 469 kg/ha and cowpea 322 kg/ha). However, due to low observed values (observed mean yield pearl millet 1,280 kg/ha and cowpea 555 kg/ha), the relative error was high, a known aspect for simulation accuracy in low‐yielding environments. The simulation experiment compared the effect of intercropping pearl millet and cowpea versus sole cropping under different plant densities and water supplies. A key finding was that intercropping pearl millet and cowpea resulted in similar total yields to the sole pearl millet. Both sole and intercrop systems responded strongly to increasing water supply, except sole cropped cowpea, which performed relatively better under low water supply. High plant density had a consistent effect, leading to lower yields under low water supply. Higher yields were achieved under high density, but only when water supply was high: absolute highest total intercrop yields were 4,000 (high density) and 3,500 kg/ha (low density). This confirms the suitability of the common practice among farmers who use the low planting density under water scarce conditions. Overall, this study confirms that intercropping is no silver bullet, i.e. not per se a way to achieve high yield production or reduce risk under drought. It does, however, provide an opportunity to diversify food production by additionally integrating protein rich crops, such as cowpea.
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Claims 19
Claim · model-written summary
APSIM captured grain yield dynamics with IA 0.91.
- Taxon
- pearl millet–cowpea
Vigna unguiculata
Cenchrus americanust0 - Outcome
- grain yieldse0
- Value
- 0.91e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“grain yields, indicated by the Willmott Index of Agreement (IA: 1 optimal, 0 the worst) 0.91 from 36 data points (n)”
t0“pearl millet–cowpea”
Claim · model-written summary
APSIM captured total biomass with IA 0.90.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Outcome
- total biomasse0
- Value
- 0.90e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“total biomass (IA: 0.90, n = 144)”
t0“pearl millet–cowpea”
Claim · model-written summary
APSIM captured leaf area index with IA 0.77.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Outcome
- leaf area indexe0
- Value
- 0.77e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf area index (LAI, IA = 0.77, n = 66)”
t0“pearl millet–cowpea”
Claim · model-written summary
APSIM captured pearl millet height with IA 0.96.
- Taxon
- pearl milletCenchrus americanuse0
- Outcome
- plant heighte0
- Value
- 0.96e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plant height (IA 0.96, n = 104 pearl millet)”
Claim · model-written summary
APSIM captured cowpea height with IA 0.81.
- Taxon
- cowpeaVigna unguiculatae0
- Outcome
- cowpeae0
- Value
- 0.81e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cowpea (IA 0.81, n = 102)”
t0“pearl millet–cowpea”
Claim · model-written summary
APSIM captured soil water with IA 0.73.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Outcome
- soil watere0
- Value
- 0.73e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soil water (IA 0.73, n = 126)”
t0“pearl millet–cowpea”
Claim · model-written summary
Pearl millet yield RMSE was 469 kg/ha.
- Taxon
- pearl milletCenchrus americanuse0
- Outcome
- RMSEe0
- Value
- 469 kg/hae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RMSE pearl millet 469 kg/ha”
Claim · model-written summary
Cowpea yield RMSE was 322 kg/ha.
- Taxon
- cowpeaVigna unguiculatae0
- Outcome
- cowpeae0
- Value
- 322 kg/hae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cowpea 322 kg/ha”
Claim · model-written summary
Relative model error was high in the low-yielding environment.
Not reportedTaxon
Verbatim
e0“the relative error was high, a known aspect for simulation accuracy in low‐yielding environments”
Claim · model-written summary
Intercropping gave similar total yield to sole pearl millet.
- Taxon
- pearl millet and cowpeaVigna unguiculataCenchrus americanuse0
- Treatment
- intercropping pearl millet and cowpeae0
- Outcome
- total yieldse0
- Direction
- similare0
- Comparator
- sole pearl millete0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“intercropping pearl millet and cowpea resulted in similar total yields to the sole pearl millet”
Claim · model-written summary
Increasing water supply raised yield in sole and intercrop systems.
- Taxon
- cowpeaVigna unguiculatae0
- Treatment
- increasing water supplye0
- Outcome
- sole and intercrop systemse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both sole and intercrop systems responded strongly to increasing water supply, except sole cropped cowpea”
Claim · model-written summary
Sole cowpea performed relatively better under low water supply.
- Taxon
- cowpeaVigna unguiculatae0
- Outcome
- performede0
- Direction
- bettere0
- Qualifier
- low water supplye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sole cropped cowpea, which performed relatively better under low water supply”
Claim · model-written summary
High plant density lowered yield under low water supply.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Treatment
- High plant densitye0
- Outcome
- yieldse0
- Direction
- lowere0
- Qualifier
- low water supplye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“High plant density had a consistent effect, leading to lower yields under low water supply.”
t0“pearl millet–cowpea”
Claim · model-written summary
High density raised yields only when water supply was high.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Treatment
- high densitye0
- Outcome
- yieldse0
- Direction
- Highere0
- Qualifier
- only when water supply was highe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Higher yields were achieved under high density, but only when water supply was high”
t0“pearl millet–cowpea”
Claim · model-written summary
The highest total intercrop yield at high density was 4,000 kg/ha.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Outcome
- total intercrop yieldse0
- Direction
- higheste0
- Value
- 4,000e0
- Qualifier
- high densitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“absolute highest total intercrop yields were 4,000 (high density) and 3,500 kg/ha (low density)”
t0“pearl millet–cowpea”
Claim · model-written summary
The highest total intercrop yield at low density was 3,500 kg/ha.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Outcome
- total intercrop yieldse0
- Direction
- higheste0
- Value
- 3,500 kg/hae0
- Qualifier
- low densitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“absolute highest total intercrop yields were 4,000 (high density) and 3,500 kg/ha (low density)”
t0“pearl millet–cowpea”
Claim · model-written summary
The authors support low planting density under water scarcity.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Outcome
- use the low planting density under water scarce conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“confirms the suitability of the common practice among farmers who use the low planting density under water scarce conditions”
t0“pearl millet–cowpea”
Claim · model-written summary
Intercropping did not inherently increase yield or reduce drought risk.
- Taxon
- pearl millet–cowpeaVigna unguiculataCenchrus americanust0
- Outcome
- not per se a way to achieve high yield production or reduce risk under droughte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“intercropping is no silver bullet, i.e. not per se a way to achieve high yield production or reduce risk under drought”
t0“pearl millet–cowpea”
Claim · model-written summary
Intercropping offers diversification through protein-rich cowpea.
- Taxon
- cowpeaVigna unguiculatae0
- Outcome
- diversify food production by additionally integrating protein rich cropse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“provide an opportunity to diversify food production by additionally integrating protein rich crops, such as cowpea”
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