Abstract
Abstract Background and aims : The concepts of critical nitrogen (N) concentration and nitrogen nutrition index (NNI) provide effective tools for assessing the N nutritional status of pastoral systems. However, no conclusive data exist concerning the effects of stubble height at harvest on the N dilution curve [N concentration (N%) = a (biomass) −b ] and mixed species cultivation on N nutritional status of forage plants with contrasting growth strategies. To evaluate these effects, three cool‐season perennial grasses (exploitative, Arrhenatherum elatius L.; moderately exploitative, Dactylis glomerata L.; conservative, Festuca arundinacea Scherb.) were grown under different cultivation methods either as pure stands or as a mixture and conducted two experiments. Methods : In experiment I, canopies of different grass species pure stands and mixtures were subjected to defoliation managements aimed to not exceed the critical LAI at harvest. Forage samples were collected from October 2015 to August 2016 to determine the N nutritional status throughout the seasons. In experiment II, half of each pure stand was mowed to 10 cm in height, and the other half to ground level. Thereafter, herbage samples were taken during regrowth to determine N dilution curves in both scenarios (from ground level and from stubble height of 10 cm). Results : We verified an NNI above 0.8 during autumn and winter for A. elatius, D. glomerata , and the mixture but only in winter for F. arundinacea . Dactylis glomerata grown in the mixture had a lower N% than its pure stand during autumn and winter, whereas A. elatius and F. arundinacea showed no differences irrespective of cultivation method throughout the year. The three forage species presented classical dilution curves when regrowth was initiated from ground level, but quadratic trends were observed when regrowth was initiated from stubble heights of 10 cm. Conclusions : Overall the N nutritional status of cool‐season perennial grasses was not affected by cultivation method when pastures were managed in conditions of non‐limiting N supply and with pre‐cut/grazing height targets derived from critical LAI measured at the full vegetative growth stage. Moreover, the N nutrition status in pastures managed under moderate/lenient defoliation should not be evaluated during periods of less intense canopy renewal and/or right after the cut/grazing events.
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Claims 9
Claim · model-written summary
Arrhenatherum elatius had an NNI above 0.8 during autumn and winter.
- Taxon
- A. elatius
Arrhenatherum elatiuse0 - Outcome
- NNIe0
- Value
- above 0.8e0
- Qualifier
- during autumn and wintere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We verified an NNI above 0.8 during autumn and winter for A. elatius, D. glomerata , and the mixture but only in winter for F. arundinacea”
Claim · model-written summary
Festuca arundinacea had an NNI above 0.8 only in winter.
- Taxon
- F. arundinacea
Lolium arundinaceume0 - Outcome
- NNIe0
- Value
- above 0.8e0
- Qualifier
- only in wintere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We verified an NNI above 0.8 during autumn and winter for A. elatius, D. glomerata , and the mixture but only in winter for F. arundinacea”
Claim · model-written summary
Dactylis glomerata grown in the mixture had a lower N% than its pure stand during autumn and winter.
- Taxon
- Dactylis glomerata
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Dactylis glomeratae2 - Treatment
- grown in the mixturee2
- Outcome
- N%e2
- Direction
- lowere2
- Qualifier
- during autumn and wintere2
- Comparator
- its pure stande2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e2“Dactylis glomerata grown in the mixture had a lower N% than its pure stand during autumn and winter”
Claim · model-written summary
Arrhenatherum elatius showed no difference in N% irrespective of cultivation method.
- Taxon
- A. elatiusArrhenatherum elatiuse3
- Treatment
- cultivation methode3
- Outcome
- N%e2
- Direction
- no differencese3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“Dactylis glomerata grown in the mixture had a lower N% than its pure stand during autumn and winter”
e3“whereas A. elatius and F. arundinacea showed no differences irrespective of cultivation method throughout the year”
Claim · model-written summary
Festuca arundinacea showed no difference in N% irrespective of cultivation method.
- Taxon
- F. arundinaceaLolium arundinaceume3
- Treatment
- cultivation methode3
- Outcome
- N%e2
- Direction
- no differencese3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“Dactylis glomerata grown in the mixture had a lower N% than its pure stand during autumn and winter”
e3“whereas A. elatius and F. arundinacea showed no differences irrespective of cultivation method throughout the year”
Claim · model-written summary
The three forage species showed classical N dilution curves when regrowth started from ground level.
Verbatim
e4“The three forage species presented classical dilution curves when regrowth was initiated from ground level”
Claim · model-written summary
The three forage species showed quadratic N dilution trends when regrowth started from a 10 cm stubble height.
Verbatim
e4“The three forage species presented classical dilution curves when regrowth was initiated from ground level”
e5“quadratic trends were observed when regrowth was initiated from stubble heights of 10 cm”
Claim · model-written summary
The N nutritional status of cool-season perennial grasses was not affected by cultivation method.
- Taxon
- perennial grassese6
- Treatment
- cultivation methode6
- Outcome
- N nutritional statuse6
- Direction
- not affectede6
Not reportedComparator
Verbatim
e6“the N nutritional status of cool‐season perennial grasses was not affected by cultivation method”
Claim · model-written summary
The N nutrition status of pastures under moderate or lenient defoliation should not be evaluated during periods of less intense canopy renewal.
Verbatim
e6“the N nutritional status of cool‐season perennial grasses was not affected by cultivation method”
e7“the N nutrition status in pastures managed under moderate/lenient defoliation should not be evaluated during periods of less intense canopy renewal”