Abstract
Abstract Agronomic biofortification of crops with zinc (Zn) can be enhanced under increased nitrogen (N) supply. Here, the effects of N fertilizer on grain Zn concentration of maize ( Zea mays L.) and cowpea ( Vigna unguiculata L.) were determined at two contrasting sites in Zimbabwe over two seasons. All treatments received soil and foliar zinc‐sulphate fertilizer. Seven N treatments, with three N rates (0, 45, and 90 kg ha −1 for maize; 0, 15, and 30 kg ha −1 for cowpea), two N forms (mineral and organic), and combinations thereof were used for each crop in a randomized complete block design ( n = 4). Maize grain Zn concentrations increased from 27.2 to 39.3 mg kg −1 across sites. At 45 kg N ha −1 , mineral N fertilizer increased maize grain Zn concentration more than organic N from cattle manure or a combination of mineral and organic N fertilizers. At 90 kg N ha −1 , the three N fertilizer application strategies had similar effects on maize grain Zn concentration. Co‐application of N and Zn fertilizer was more effective at increasing Zn concentration in maize grain than Zn fertilizer alone. Increases in cowpea grain Zn concentration were less consistent, although grain Zn concentration increased from 39.8 to 52.7 mg kg −1 under optimal co‐applications of N and Zn. Future cost/benefit analyses of agronomic biofortification need to include information on benefits of agro‐fortified grain, complex farmer management decisions (including cost and access to both N and Zn fertilizers), as well as understanding of the spatial and site‐specific variation in fertilizer responses.
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Claims 7
Claim · model-written summary
Maize grain zinc concentration increased across sites from 27.2 to 39.3 mg kg −1.
- Outcome
- grain Zn concentrationse0
- Direction
- increasede0
- Value
- 27.2 to 39.3 mg kg −1e0
- Setting
- across sitese0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize grain Zn concentrations increased from 27.2 to 39.3 mg kg −1 across sites”
Claim · model-written summary
At 45 kg N ha −1, mineral N increased maize grain zinc more than organic or combined N.
- Treatment
- 45 kg N ha −1 , mineral N fertilizere0
- Outcome
- grain Zn concentratione0
- Direction
- increasede0
- Comparator
- organic N from cattle manure or a combination of mineral and organic N fertilizerse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 45 kg N ha −1 , mineral N fertilizer increased maize grain Zn concentration more than organic N from cattle manure or a combination of mineral and organic N fertilizers”
Claim · model-written summary
At 90 kg N ha −1, the three N strategies had similar effects on maize grain zinc.
- Treatment
- 90 kg N ha −1e0
- Outcome
- grain Zn concentratione0
- Direction
- similare0
- Comparator
- three N fertilizer application strategiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 90 kg N ha −1 , the three N fertilizer application strategies had similar effects on maize grain Zn concentration”
Claim · model-written summary
N and Zn together increased maize grain zinc more effectively than Zn alone.
- Treatment
- Co‐application of N and Zn fertilizere0
- Outcome
- Zn concentration in maize graine0
- Direction
- increasinge0
- Comparator
- Zn fertilizer alonee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Co‐application of N and Zn fertilizer was more effective at increasing Zn concentration in maize grain than Zn fertilizer alone”
Claim · model-written summary
Cowpea grain zinc responses were less consistent.
- Taxon
- cowpea
Vigna unguiculatae0 - Outcome
- grain Zn concentratione0
- Direction
- Increasese0
- Qualifier
- less consistente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increases in cowpea grain Zn concentration were less consistent”
Claim · model-written summary
Under optimal N and Zn co-application, cowpea grain zinc rose from 39.8 to 52.7 mg kg −1.
- Taxon
- cowpeaVigna unguiculatat0
- Treatment
- optimal co‐applications of N and Zne0
- Outcome
- grain Zn concentratione0
- Direction
- increasede0
- Value
- 39.8 to 52.7 mg kg −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“grain Zn concentration increased from 39.8 to 52.7 mg kg −1 under optimal co‐applications of N and Zn”
t0“cowpea”
Claim · model-written summary
The authors recommend considering fortified-grain benefits, farmer management, fertilizer access and spatial variation in future cost-benefit analyses.
Verbatim
e0“Future cost/benefit analyses of agronomic biofortification need to include information on benefits of agro‐fortified grain, complex farmer management decisions (including cost and access to both N and Zn fertilizers), as well as understanding of the spatial and site‐specific variation in fertilizer responses”
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