Abstract
Environmental legislation may impose limitations on the quantity of nitrogen (N) used in corn production on the basis of soil type and ground water flow. If N rates are reduced, this might influence the relative competitiveness of weed species. Therefore, the objectives of this research were to develop a surface response model to provide estimations of the effect of differing N rates on threshold values of green foxtail in corn and to use this model as a theoretical framework for hypothesis testing. Field experiments were conducted from 1999 to 2001 to examine the interaction of N rate and green foxtail density on corn grain yield. The experiment was designed as a two-factor factorial with N levels ranging from 0 to 200 kg N ha −1 and targeted green foxtail densities ranging from 0 to 300 green foxtail plants m −2 . The addition of up to 200 kg N ha −1 increased corn grain yield in both weed-free and weedy treatments. Corn yield loss attributed to green foxtail ranged from 35 to 40% at 0 kg N ha −1 to 12 to 17% at 200 kg N ha −1 . Ridge analysis of the response surfaces indicated that optimal corn grain yield could be achieved at derived values of 131 to 138 kg N ha −1 while maintaining a green foxtail density of 8 to 9 green foxtail plants m −2 on a sandy soil with less than 2% organic matter. The analyses of simulation results led to the generation of hypotheses of practical relevance to N management. On the basis of the generated hypotheses, a legislated reduction in N or an increase in the cost of N fertilizer would result in a lower threshold value for green foxtail in corn. If legislation were to ban the use of all herbicides in corn production, higher N rates or an increase in mechanical weed control measures would be required to offset yield losses caused by green foxtail. The human health and environmental consequences of such legislation would be significant.
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Claims 6
Claim · model-written summary
Adding up to 200 kg N per hectare increased corn grain yield in both weed-free and weedy treatments.
- Taxon
- corn
Zea mays subsp. mayse1 - Treatment
- up to 200 kg N ha −1e1
- Outcome
- corn grain yielde1
- Direction
- increasede1
- Qualifier
- in both weed-free and weedy treatmentse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The addition of up to 200 kg N ha −1 increased corn grain yield in both weed-free and weedy treatments”
Claim · model-written summary
Corn yield loss attributed to green foxtail was 35 to 40% at 0 kg N per hectare.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- 0 kg N ha −1e1
- Interactor
- green foxtaile1weed
- Outcome
- Corn yield losse1
- Value
- 35 to 40%e1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Corn yield loss attributed to green foxtail ranged from 35 to 40% at 0 kg N ha −1 to 12 to 17% at 200 kg N ha −1”
Claim · model-written summary
Corn yield loss attributed to green foxtail was 12 to 17% at 200 kg N per hectare.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- 200 kg N ha −1e1
- Interactor
- green foxtaile1weed
- Outcome
- Corn yield losse1
- Value
- 12 to 17%e1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Corn yield loss attributed to green foxtail ranged from 35 to 40% at 0 kg N ha −1 to 12 to 17% at 200 kg N ha −1”
Claim · model-written summary
Ridge analysis indicated optimal corn grain yield at 131 to 138 kg N per hectare while keeping green foxtail at 8 to 9 plants per square metre on sandy soil.
- Taxon
- cornZea mays subsp. mayse1
- Interactor
- green foxtaile1weed
- Outcome
- optimal corn grain yielde1
- Value
- 131 to 138 kg N ha −1e1
- Qualifier
- while maintaining a green foxtail density of 8 to 9 green foxtail plants m −2e1
- Setting
- sandy soil with less than 2% organic mattere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Ridge analysis of the response surfaces indicated that optimal corn grain yield could be achieved at derived values of 131 to 138 kg N ha −1 while maintaining a green foxtail density of 8 to 9 green foxtail plants m −2 on a sandy soil with less than 2% organic matter”
Claim · model-written summary
A legislated reduction in N would lower the green foxtail threshold in corn (hypothesis from simulation).
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- a legislated reduction in Ne1
- Interactor
- green foxtaile1weed
- Outcome
- threshold value for green foxtaile1
- Direction
- lowere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“a legislated reduction in N or an increase in the cost of N fertilizer would result in a lower threshold value for green foxtail in corn”
Claim · model-written summary
A ban on all herbicides in corn would require higher N rates or more mechanical weed control to offset green foxtail yield losses (hypothetical).
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- ban the use of all herbicidese1
- Interactor
- green foxtaile1weed
- Outcome
- yield lossese1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“If legislation were to ban the use of all herbicides in corn production, higher N rates or an increase in mechanical weed control measures would be required to offset yield losses caused by green foxtail”
The same questions in other papers
nitrogen · yield · Zea mays (maize)Positive and negative results
1,905 papers in the same direction as this paper · 234 in the opposite direction · 45 reporting no difference from an alternative
- no effect
- positive
- positive
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