Abstract
Abstract Nitrification inhibitors (NIs) such as dicyandiamide (DCD) and nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine] (NP) slow the nitrification process, thus reducing N losses from leaching and denitrification. In field studies (1990–1994) on a Renfrow silt loam (fine‐silty, mixed, thermic Udertic Paleustolls) near El Reno, OK, we evaluated these two NIs and their placement effects on nitrification of applied urea in soils and on wheat ( Triticum aestivum L.) yields. Urea at 60 kg N ha −1 treated with or without NIs was placed 3 to 4 cm below the seed (BL) at seeding or was broadcast (BR) after seeding on the day of seeding, with no N as control. Mineral N forms were determined in the 0‐ to 30‐cm soil zone in fall and spring. Differences in soil mineral N concentration below the 10‐cm depth were minimal (but higher than the control) in all N treatments. In the 0‐ to 10‐cm depth, BL placement of NI‐treated urea significantly reduced nitrification in the fall compared with BR urea with or without NIs, except in 1994. Soil mineral N content in spring was similar with either placement of NI‐treated urea, but was significantly greater than untreated BR urea. Warm temperatures and dry soil in the fall tended to reduce the effectiveness of surface‐applied NIs. The highest NH 4 + percentage in total soil mineral N was observed with DCD BL or NP BL, followed by NP BR and DCD BR. Urea treated with NIs increased grain yield from 7 to 31% above untreated urea. Grain yield was highest with DCD BL (31%), followed by DCD BR (26%) and NP BR (24%), compared with the broadcast untreated urea. Grain N yield was 140 g kg −1 greater with DCD‐N than with untreated urea. Deep placement of DCD under no‐till winter wheat in the southern Great Plains can reduce nitrification and increase N availability under varying year‐to‐year environmental conditions and can improve wheat grain yield and grain N compared with surface broadcast of urea with or without NI.
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Claims 12
Claim · model-written summary
Banded (BL) placement of NI-treated urea significantly reduced fall nitrification in the 0-10 cm depth compared with broadcast urea with or without NIs, except in 1994.
- Taxon
- wheat
Triticum aestivume2 - Treatment
- BL placement of NI‐treated ureae1
- Outcome
- nitrification in the falle1
- Direction
- reducede1
- Qualifier
- except in 1994e1
- Comparator
- BR urea with or without NIse1
- Setting
- El Reno, OKe3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In the 0‐ to 10‐cm depth, BL placement of NI‐treated urea significantly reduced nitrification in the fall compared with BR urea with or without NIs, except in 1994”
e2“wheat ( Triticum aestivum L.) yields”
e3“In field studies (1990–1994) on a Renfrow silt loam (fine‐silty, mixed, thermic Udertic Paleustolls) near El Reno, OK”
Claim · model-written summary
Spring soil mineral N content was similar between the two placements of NI-treated urea.
- Taxon
- wheatTriticum aestivume2
- Treatment
- placement of NI‐treated ureae1
- Outcome
- Soil mineral N content in springe1
- Direction
- no_changeinferrede1
- Comparator
- either placemente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Soil mineral N content in spring was similar with either placement of NI‐treated urea”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
Spring soil mineral N content with NI-treated urea was significantly greater than with untreated broadcast urea.
- Taxon
- wheatTriticum aestivume2
- Treatment
- NI‐treated ureae1
- Outcome
- Soil mineral N content in springe1
- Direction
- greatere1
- Comparator
- untreated BR ureae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Soil mineral N content in spring was similar with either placement of NI‐treated urea, but was significantly greater than untreated BR urea”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
The highest NH4+ share of total soil mineral N was observed with DCD BL or NP BL, followed by NP BR and DCD BR.
- Taxon
- wheatTriticum aestivume2
- Treatment
- DCD BL or NP BLe1
- Outcome
- NH 4 + percentage in total soil mineral Ne1
- Direction
- higheste1
- Comparator
- NP BR and DCD BRe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The highest NH 4 + percentage in total soil mineral N was observed with DCD BL or NP BL, followed by NP BR and DCD BR”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
Urea treated with NIs increased wheat grain yield by 7 to 31% above untreated urea.
- Taxon
- wheatTriticum aestivume2
- Treatment
- Urea treated with NIse1
- Outcome
- grain yielde1
- Direction
- increasede1
- Value
- 7 to 31%e1
- Comparator
- untreated ureae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Urea treated with NIs increased grain yield from 7 to 31% above untreated urea”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
Grain yield was highest with DCD BL, 31% above broadcast untreated urea.
- Taxon
- wheatTriticum aestivume2
- Treatment
- DCD BLe1
- Outcome
- Grain yielde1
- Direction
- higheste1
- Value
- 31%e1
- Comparator
- broadcast untreated ureae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Grain yield was highest with DCD BL (31%), followed by DCD BR (26%) and NP BR (24%), compared with the broadcast untreated urea”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
Grain yield with DCD BR was 26% above broadcast untreated urea, second to DCD BL.
- Taxon
- wheatTriticum aestivume2
- Treatment
- DCD BRe1
- Outcome
- Grain yielde1
- Direction
- higherinferrede1
- Value
- 26%e1
- Comparator
- broadcast untreated ureae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Grain yield was highest with DCD BL (31%), followed by DCD BR (26%) and NP BR (24%), compared with the broadcast untreated urea”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
Grain yield with NP BR was 24% above broadcast untreated urea.
- Taxon
- wheatTriticum aestivume2
- Treatment
- NP BRe1
- Outcome
- Grain yielde1
- Direction
- higherinferrede1
- Value
- 24%e1
- Comparator
- broadcast untreated ureae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Grain yield was highest with DCD BL (31%), followed by DCD BR (26%) and NP BR (24%), compared with the broadcast untreated urea”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
Grain N yield was 140 g kg-1 greater with DCD-N than with untreated urea.
- Taxon
- wheatTriticum aestivume2
- Treatment
- DCD‐Ne1
- Outcome
- Grain N yielde1
- Direction
- greatere1
- Value
- 140 g kg −1e1
- Comparator
- untreated ureae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Grain N yield was 140 g kg −1 greater with DCD‐N than with untreated urea”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
Deep placement of DCD under no-till winter wheat in the southern Great Plains can reduce nitrification and increase N availability across years.
- Taxon
- winter wheatTriticum aestivume1
- Outcome
- Deep placement of DCDe1
- Setting
- southern Great Plainse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Deep placement of DCD under no‐till winter wheat in the southern Great Plains can reduce nitrification and increase N availability under varying year‐to‐year environmental conditions”
Claim · model-written summary
Warm temperatures and dry soil in the fall tended to reduce the effectiveness of surface-applied NIs.
- Taxon
- wheatTriticum aestivume2
- Treatment
- Warm temperatures and dry soil in the falle1
- Outcome
- effectiveness of surface‐applied NIse1
- Direction
- reducee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Warm temperatures and dry soil in the fall tended to reduce the effectiveness of surface‐applied NIs”
e2“wheat ( Triticum aestivum L.) yields”
Claim · model-written summary
Soil mineral N concentration below the 10-cm depth was minimally higher than the control in all N treatments.
- Taxon
- wheatTriticum aestivume2
- Treatment
- N treatmentse1
- Outcome
- soil mineral N concentration below the 10‐cm depthe1
- Direction
- highere1
- Qualifier
- minimale1
- Comparator
- controle1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Differences in soil mineral N concentration below the 10‐cm depth were minimal (but higher than the control) in all N treatments”
e2“wheat ( Triticum aestivum L.) yields”
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