Abstract
Abstract Optimum fertilizer nitrogen (N) rates are highly variable from one production corn (Zea mays L.) field to another, but producers usually use about the same N rate over their whole farm. Matching N application rates to actual crop need could have both economic and environmental benefits. The objectives of this research were to evaluate soil and plant tests for their ability to predict optimum N rates across a range of production cornfields in Missouri, and to evaluate the economic performance of recommendation systems based on these measurements. Yield response to N was measured in each experiment, along with soil mineral N measurements (planting and sidedress), tissue N at sidedress time, and chlorophyll meter reading at sidedress time. Optimum N fertilizer rates were fairly evenly spread from 0 to 235 kg N ha−1 in these sixteen experiments. Soil N measurements, tissue N at sidedress, and chlorophyll meter reading at sidedress were all clearly related to optimum N rate—the higher the test result, the lower the optimum N rate. Plant measurements (tissue N content and chlorophyll meter reading) were more strongly related to optimum N rate than were any of the soil measurements. Only two of the recommendation systems tested significantly increased profit (by $17 to 20 ha−1) relative to N rates used by producers in these fields: 1) subtracting both traditional credits (for manure, alfalfa [Medicago sativa L.], or soybean [Glycine max L.]) and a preplant soil nitrate credit from current University of Missouri recommendations, or 2) using sidedress tissue N content to predict sidedress N rate. Three other systems reduced N rates significantly relative to producer N rates without reducing profits: 1) chlorophyll meter to predict sidedress N rate, 2) sidedress soil nitrate test with the critical value adjusted for wet springs, and 3) University of Missouri recommendations with history credits only. *Contribution from the Missouri Agricultural Experiment Station. Journal Series Number 12,767. ACKNOWLEDGMENTS I would like to thank Gordon Hauck, John Hoff, Richard Lenz, Mark Rothermich, Raymond Boland, Wayne Kurtz, Steve Milne, Vernon and Tim Echelmeier, Linus Rothermich, and Ron Sommer for their cooperation, comments, and generosity in allowing me to work on their farms. For help with the field work, I am grateful to Carrie Ferguson, Tonya Mueller, Eric Bohle, Yi Chang Sun, John Lory, Dave Hoehne, Zeke Long, and John Stecker. This work was made possible by financial support from the Missouri Commercial Agriculture Program and the Barbee Fund. Notes *Contribution from the Missouri Agricultural Experiment Station. Journal Series Number 12,767.
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Claims 8
Claim · model-written summary
Optimum N fertilizer rates for corn ranged from 0 to 235 kg N ha−1 across sixteen experiments.
- Taxon
- corn
Zea mays subsp. mayse0 - Outcome
- Optimum N fertilizer ratese1
- Value
- 0 to 235 kg N ha−1e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“production corn (Zea mays L.) field”
e1“Optimum N fertilizer rates were fairly evenly spread from 0 to 235 kg N ha−1 in these sixteen experiments”
Claim · model-written summary
Soil N, tissue N and chlorophyll meter readings at sidedress were associated with lower optimum N rate in corn; the higher the test result, the lower the rate.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- optimum N ratee2
- Direction
- lowere2
- Qualifier
- the higher the test resulte2
- Setting
- Missourie3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“production corn (Zea mays L.) field”
e2“Soil N measurements, tissue N at sidedress, and chlorophyll meter reading at sidedress were all clearly related to optimum N rate—the higher the test result, the lower the optimum N rate”
e3“across a range of production cornfields in Missouri”
Claim · model-written summary
Plant measurements (tissue N content and chlorophyll meter reading) were more strongly related to optimum N rate in corn than soil measurements.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- optimum N ratee4
- Comparator
- soil measurementse4
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“production corn (Zea mays L.) field”
e4“Plant measurements (tissue N content and chlorophyll meter reading) were more strongly related to optimum N rate than were any of the soil measurements”
Claim · model-written summary
Subtracting traditional credits and a preplant soil nitrate credit from University of Missouri recommendations significantly increased profit in corn relative to producer N rates.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- subtracting both traditional credits (for manure, alfalfa [Medicago sativa L.], or soybean [Glycine max L.]) and a preplant soil nitrate credit from current University of Missouri recommendationse5
- Outcome
- profite5
- Direction
- increasede5
- Value
- $17 to 20 ha−1e5
- Comparator
- N rates used by producerse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“production corn (Zea mays L.) field”
e5“Only two of the recommendation systems tested significantly increased profit (by $17 to 20 ha−1) relative to N rates used by producers in these fields: 1) subtracting both traditional credits (for manure, alfalfa [Medicago sativa L.], or soybean [Glycine max L.]) and a preplant soil nitrate credit from current University of Missouri recommendations, or 2) using sidedress tissue N content to predict sidedress N rate”
Claim · model-written summary
Using sidedress tissue N content to predict sidedress N rate significantly increased profit in corn relative to producer N rates.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- using sidedress tissue N content to predict sidedress N ratee5
- Outcome
- profite5
- Direction
- increasede5
- Value
- $17 to 20 ha−1e5
- Comparator
- N rates used by producerse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“production corn (Zea mays L.) field”
e5“Only two of the recommendation systems tested significantly increased profit (by $17 to 20 ha−1) relative to N rates used by producers in these fields: 1) subtracting both traditional credits (for manure, alfalfa [Medicago sativa L.], or soybean [Glycine max L.]) and a preplant soil nitrate credit from current University of Missouri recommendations, or 2) using sidedress tissue N content to predict sidedress N rate”
Claim · model-written summary
Chlorophyll meter to predict sidedress N rate significantly reduced N rates in corn without reducing profits.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- chlorophyll meter to predict sidedress N ratee6
- Outcome
- N ratese6
- Direction
- reducede6
- Qualifier
- without reducing profitse6
- Comparator
- producer N ratese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“production corn (Zea mays L.) field”
e6“Three other systems reduced N rates significantly relative to producer N rates without reducing profits: 1) chlorophyll meter to predict sidedress N rate, 2) sidedress soil nitrate test with the critical value adjusted for wet springs, and 3) University of Missouri recommendations with history credits only”
Claim · model-written summary
Sidedress soil nitrate test with the critical value adjusted for wet springs significantly reduced N rates in corn without reducing profits.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- sidedress soil nitrate test with the critical value adjusted for wet springse6
- Outcome
- N ratese6
- Direction
- reducede6
- Qualifier
- without reducing profitse6
- Comparator
- producer N ratese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“production corn (Zea mays L.) field”
e6“Three other systems reduced N rates significantly relative to producer N rates without reducing profits: 1) chlorophyll meter to predict sidedress N rate, 2) sidedress soil nitrate test with the critical value adjusted for wet springs, and 3) University of Missouri recommendations with history credits only”
Claim · model-written summary
University of Missouri recommendations with history credits only significantly reduced N rates in corn without reducing profits.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- University of Missouri recommendations with history credits onlye6
- Outcome
- N ratese6
- Direction
- reducede6
- Qualifier
- without reducing profitse6
- Comparator
- producer N ratese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“production corn (Zea mays L.) field”
e6“Three other systems reduced N rates significantly relative to producer N rates without reducing profits: 1) chlorophyll meter to predict sidedress N rate, 2) sidedress soil nitrate test with the critical value adjusted for wet springs, and 3) University of Missouri recommendations with history credits only”
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