Abstract
Abstract This study examines historical maize production in the U.S. Corn Belt and the impact of weather variability on yields using crop reporting districts (CRDs) in Illinois, Indiana, Iowa, and Nebraska. We used the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI), to evaluate the reliability of predicting district-level yields using the national commodity crop productivity index (NCCPI). Corn yield data were sourced from the USDA’s NASS Quick Stats database, covering three periods: 1929–1959 (first hybrid genotypes), 1960–1979 (rise of agrochemicals), and 1980–2022 (advancements in biotechnology and knowledge). We assessed the relationships between annual yield and the NCCPI, SPI, and SPEI through regression analysis. Corn yield showed a significant linear increase with the passage of time across all evaluated periods and CRDs, with an average increase of 113 kg per hectare per year. Some Nebraska districts recorded peaks exceeding 150 kg per hectare per year between 1960 and 1980. Factors influencing corn production have changed over time, and consequently, the NCCPI has become less robust for predicting corn yield since 1960. While corn yields demonstrated greater variability in earlier periods, stability has improved in recent years. The strongest relationship between historic relative yields (RYs) (actual yields divided by predicted yields) and precipitation indices was observed in central Illinois and northwestern Indiana; several CRDs in Nebraska showed weaker relationships. Notably, SPI during July is the most significant factor related to changes in historic RYs, impacting yields in 11 of the 35 CRDs in the central U.S. Corn Belt.
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Claims 7
Claim · model-written summary
Corn yield rose across periods and districts by an average 113 kg per hectare per year.
- Taxon
- Corn
Zea mays subsp. mayst0 - Outcome
- Corn yielde0
- Direction
- increasee0
- Value
- 113 kg per hectare per yeare0
- Setting
- CRDse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Corn yield showed a significant linear increase with the passage of time across all evaluated periods and CRDs, with an average increase of 113 kg per hectare per year”
t0“corn”
Claim · model-written summary
Some Nebraska districts exceeded 150 kg per hectare per year in 1960–1980.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- peakse0
- Direction
- exceedinge0
- Value
- 150 kg per hectare per yeare0
- Setting
- Nebraskae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Some Nebraska districts recorded peaks exceeding 150 kg per hectare per year between 1960 and 1980”
t0“corn”
Claim · model-written summary
NCCPI became less robust for predicting corn yield since 1960.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- predicting corn yielde0
- Direction
- less robuste0
- Value
- 1960e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the NCCPI has become less robust for predicting corn yield since 1960”
t0“corn”
Claim · model-written summary
Corn yield stability improved in recent years.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- stabilitye0
- Direction
- improvede0
- Comparator
- earlier periodse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“corn yields demonstrated greater variability in earlier periods, stability has improved in recent years”
t0“corn”
Claim · model-written summary
Relative yields had their strongest precipitation-index relationship in central Illinois and northwestern Indiana.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- relationship between historic relative yields (RYs) (actual yields divided by predicted yields) and precipitation indicese0
- Setting
- central Illinois and northwestern Indianae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The strongest relationship between historic relative yields (RYs) (actual yields divided by predicted yields) and precipitation indices was observed in central Illinois and northwestern Indiana”
t0“corn”
Claim · model-written summary
Several Nebraska districts had weaker precipitation-index relationships.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- weaker relationshipse0
- Direction
- weakere0
- Setting
- Nebraskae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“several CRDs in Nebraska showed weaker relationships”
t0“corn”
Claim · model-written summary
July SPI was the most significant factor related to historic relative yield change in 11 of 35 districts.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- changes in historic RYse0
- Value
- 11 of the 35 CRDse0
- Setting
- central U.S. Corn Belte0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPI during July is the most significant factor related to changes in historic RYs, impacting yields in 11 of the 35 CRDs in the central U.S. Corn Belt”
t0“corn”