Abstract
Abstract Knowing a cover crop's carbon to nitrogen (C/N) ratio can help growers time termination to optimize N release. But growers lack simple methods to predict important C/N ratios like 20, an often‐cited “tipping point” between N mineralization and immobilization. We evaluated if Feekes growth stage, days after planting (DAP), and growing degree days (GDD) could predict C/N ratio changes of cereal cover crops. We tracked C/N changes monthly in rye ( Secale cereale L. ‘Merced’) and triticale (x Triticosecale Wittmack, ‘Pacheco’) in five biweekly trials sown from October 1 to November 30, 2021, and related these changes to farmer‐friendly metrics: DAP, GDD, and development. Growth stage and GDD were strongly correlated, as were DAP and C/N. The C/N ratios (1) increased with increasing GDD, DAP, and growth stage, (2) were similar for both cereals, and (3) became more variable over time. With exception of one trial, planted on November 15 where N was more limited, shoot biomass reached a C/N ratio of 20 when October‐planted cover crops were at Feekes 10.1 (heading, 97–103 DAP) and Feekes 8 (flag leaf just visible, 94–98 DAP) in November plantings. Excluding the 15 Nov. trial, fitted regressio curves up to ≈150 DAP showed that a C/N of 20 occurred by 94 to 102 DAP, for October‐ and November‐plantings, respectively. Accumulated GDD to reach a C/N of 20 varied with planting date ranging from approximately 650 to 900 GDD, and tended to decrease with later plantings. Our data illustrate the value and complexity of using growth stage, GDD, and DAP to predict the C/N ratio changes in cover crops. This will help farmers optimize cover crop management and comply with a new California regulation to reduce N leaching to groundwater.
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The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 10
Claim · model-written summary
Growth stage and growing degree days were strongly correlated in rye and triticale cover crops.
- Taxon
- rye and triticale
Secale cereale
×Triticosecalet0 - Outcome
- Growth stagee0
- Direction
- strongly correlatede0
- Comparator
- GDDe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“Growth stage and GDD were strongly correlated”
Claim · model-written summary
Days after planting and C/N ratio were strongly correlated in rye and triticale cover crops.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Outcome
- C/Ne0
- Direction
- as weree0
- Comparator
- DAPe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“as were DAP and C/N”
Claim · model-written summary
The C/N ratios of the cover crops increased with increasing GDD, DAP and growth stage.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Outcome
- C/N ratiose0
- Direction
- increasede1
- Comparator
- GDD, DAP, and growth stagee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“The C/N ratios”
e1“increased with increasing GDD, DAP, and growth stage”
Claim · model-written summary
The C/N ratios were similar for rye and triticale.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Outcome
- C/N ratiose0
- Qualifier
- were similar for both cerealse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“The C/N ratios”
e1“were similar for both cereals”
Claim · model-written summary
The C/N ratios became more variable over time.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Outcome
- C/N ratiose0
- Qualifier
- became more variable over timee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“The C/N ratios”
e1“became more variable over time”
Claim · model-written summary
Shoot biomass of October-planted cover crops reached a C/N ratio of 20 at Feekes 10.1 (heading), 97-103 days after planting.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Outcome
- C/N ratio of 20e0
- Value
- 97–103 DAPe1
- Qualifier
- October‐planted cover crops were at Feekes 10.1e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“shoot biomass reached a C/N ratio of 20”
e1“October‐planted cover crops were at Feekes 10.1 (heading, 97–103 DAP)”
Claim · model-written summary
Shoot biomass of November-planted cover crops reached a C/N ratio of 20 at Feekes 8 (flag leaf just visible), 94-98 days after planting.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Outcome
- C/N ratio of 20e0
- Value
- 94–98 DAPe1
- Qualifier
- Feekes 8 (flag leaf just visible, 94–98 DAP) in November plantingse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“shoot biomass reached a C/N ratio of 20”
e1“Feekes 8 (flag leaf just visible, 94–98 DAP) in November plantings”
Claim · model-written summary
Fitted regression curves showed a C/N of 20 occurring by 94 to 102 days after planting for October and November plantings, respectively.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Outcome
- C/N of 20e0
- Value
- 94 to 102 DAPe0
- Qualifier
- for October‐ and November‐plantingse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“a C/N of 20 occurred by 94 to 102 DAP, for October‐ and November‐plantings, respectively”
Claim · model-written summary
Accumulated GDD to reach a C/N of 20 varied with planting date, ranging from approximately 650 to 900 GDD.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Outcome
- Accumulated GDD to reach a C/N of 20e0
- Value
- approximately 650 to 900 GDDe0
- Qualifier
- varied with planting datee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“Accumulated GDD to reach a C/N of 20 varied with planting date ranging from approximately 650 to 900 GDD”
Claim · model-written summary
Accumulated GDD to reach a C/N of 20 tended to decrease with later plantings.
- Taxon
- rye and triticaleSecale cereale×Triticosecalet0
- Treatment
- later plantingse1
- Outcome
- Accumulated GDD to reach a C/N of 20e0
- Direction
- decreasee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“rye and triticale cover crops”
e0“Accumulated GDD to reach a C/N of 20”
e1“tended to decrease with later plantings”