Abstract
The challenge for variable N rate management is to identify specific field areas that respond to specific N levels. We evaluated two corn ( Zea mays L.) hybrids at two N rates (110–130 vs. 165–185 kg ha −1 at three sites and manure vs. manure + 55 kg ha −1 at two sites) to determine if corn responded differently to N and hybrids within fields. Spatial yield variability existed at all sites in dry years (1999 and 2001) but at only two sites in a wet year (2000). Spatial yield difference variability in response to N existed at only two of 13 site–year comparisons. Although late‐spring soil NO 3 –N concentrations in the upper 30 cm were <25 mg kg −1 on 15 to 25% of the manured fields in the wet year, spatial yield difference variability in response to N did not exist. At a nonmanured site, spatial yield difference variability in response to N existed with temporal yield stability across dry years ( r = 0.96). Surprisingly, corn responded to the higher N rate on 25% of this field where yields were least, but not where yields were greatest. Apparently, variable N rate management of corn requires more information than soil NO 3 –N concentrations and yield maps. Spatial yield difference variability between hybrids existed at only four of 15 site–year comparisons, despite hybrid interactions with sites. Adoption of variable hybrid selection is unlikely if hybrids that show interactions with sites do not show spatial yield difference variability within sites.
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Claims 10
Claim · model-written summary
Spatial yield variability existed at all sites in dry years (1999 and 2001).
- Taxon
- corn
Zea mays subsp. mayse0 - Outcome
- spatial yield variabilitye1
- Qualifier
- at all sites in dry years (1999 and 2001)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e1“Spatial yield variability existed at all sites in dry years (1999 and 2001) but at only two sites in a wet year (2000)”
Claim · model-written summary
Spatial yield variability existed at only two sites in a wet year (2000).
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- spatial yield variabilitye1
- Value
- only two sitese1
- Qualifier
- in a wet year (2000)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e1“Spatial yield variability existed at all sites in dry years (1999 and 2001) but at only two sites in a wet year (2000)”
Claim · model-written summary
Spatial yield difference variability in response to N existed at two of 13 site–year comparisons.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- spatial yield difference variability in response to Ne2
- Value
- two of 13 site–year comparisonse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e2“Spatial yield difference variability in response to N existed at only two of 13 site–year comparisons”
Claim · model-written summary
At a nonmanured site, temporal yield stability across dry years was associated with spatial yield difference variability in response to N (r = 0.96).
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- temporal yield stability across dry yearse4
- Value
- r = 0.96e4
- Qualifier
- At a nonmanured sitee4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e4“At a nonmanured site, spatial yield difference variability in response to N existed with temporal yield stability across dry years ( r = 0.96)”
Claim · model-written summary
Corn responded to the higher N rate on 25% of a field where yields were least, but not where yields were greatest.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- higher N ratee5
- Outcome
- responded to the higher N ratee5
- Value
- 25%e5
- Qualifier
- where yields were leaste5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e5“Surprisingly, corn responded to the higher N rate on 25% of this field where yields were least, but not where yields were greatest”
Claim · model-written summary
Spatial yield difference variability between hybrids existed at four of 15 site–year comparisons.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- spatial yield difference variability between hybridse6
- Value
- four of 15 site–year comparisonse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e6“Spatial yield difference variability between hybrids existed at only four of 15 site–year comparisons”
Claim · model-written summary
Spatial yield difference variability in response to N did not exist in the wet year on manured fields.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- spatial yield difference variability in response to Ne3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e3“spatial yield difference variability in response to N did not exist”
Claim · model-written summary
Soil NO3-N concentrations in the upper 30 cm were below 25 mg/kg on some manured fields in the wet year.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- soil NO 3 –N concentrationse7
- Value
- <25 mg kg −1e7
- Qualifier
- in the wet yeare7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e7“soil NO 3 –N concentrations in the upper 30 cm were <25 mg kg −1 on 15 to 25% of the manured fields in the wet year”
Claim · model-written summary
Variable N rate management of corn requires more information than soil NO3-N concentrations and yield maps.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- variable N rate managemente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e1“Apparently, variable N rate management of corn requires more information than soil NO 3 –N concentrations and yield maps”
Claim · model-written summary
Adoption of variable hybrid selection is unlikely when hybrids interact with sites but show no spatial yield difference variability within sites.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- variable hybrid selectione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We evaluated two corn ( Zea mays L.) hybrids at two N rates”
e1“Adoption of variable hybrid selection is unlikely if hybrids that show interactions with sites do not show spatial yield difference variability within sites”