Late-season fertilization of <i>Picea mariana</i> seedlings: intensive loading and outplanting response on greenhouse bioassays
Bibliographic record
Abstract
Traditional greenhouse culture involves a late-season hardening period that withholds irrigation and fertilization from black spruce seedlings to promote frost-hardiness.Since nutrient uptake is limited without supplemental fertilization, growth during hardening may lead to internal nutrient dilution, a condition detrimental to field performance of seedlings.We examine whether late-season fertilization, applied as intensive loading, will counter dilution and build up nutrient reserves in seedlings reared conventionally or nutrient loaded before hardening.A mixed NPK fertilizer delivering 0, 12, 24, or, 48 mg N•seedling -1 for 9 weeks after bud set was tested.Root and shoot dry mass increased as much as 104 and 42% during hardening.Seedling biomass, however, was unchanged by late-season fertilization, but N uptake was increased 44-167% signifying induced luxury consumption.Extra K supplementation of treatments averted K dilution in plant tissues often occurring with high N addition.A 13-week outplanting trial on intact soil bioassays retrieved from a boreal site showed that growth and nutrient allocation were significantly enhanced by larger N reserves built up after intensive nutrient loading.About 72-80% of N required for new shoot growth was met from internal cycling, demonstrating the capacity of loading to enhance retranslocation.Intermediate loading (24 mg N) was most effective in promoting N accumulation and outplanting growth of both seedling types.Survival was reduced (30%) only at the highest dose.Study results demonstrate the potential advantage of these practices to improve growth of newly planted seedlings on northern forest sites.black spruce / hardening period / nitrogen / nutrient loading / retranslocation / super-loading Résumé -Fertilisation tardive de semis de Picea mariana : apport intensif et réponse après plantation en serre d'essais biologiques.Les cultures traditionnelles en serre comportent une période tardive d'endurcissement qui retarde l'irrigation et la fertilisation des semis de Picea mariana pour promouvoir l'endurcissement au froid.Puisque le prélèvement de nutriments est limité sans supplémentation de fertilisation, la croissance pendant la période d'endurcissement peut conduire à une dilution interne des nutriments, une situation préjudiciable pour les performances au champ des plants.Nous avons examiné si la fertilisation tardive, appliquée par des apports massifs peut contrebalancer la dilution et accroître les réserves de nutriments dans les semis élevés conventionnellement ou les nutriments apportés avant l'endurcissement.On a testé un mélange de fertilisant NPK libérant 0,12, 24 ou 48 mg d'azote par semis pendant 9 semaines après le débourrement.Le poids sec des racines et des pousses s'est accru de 104 et 42 % pendant l'endurcissement.Cependant la biomasse des semis a été inchangée par une fertilisation tardive, mais le prélèvement d'azote s'est accru de 44 à 167 %, indiquant une consommation de luxe.Une supplémentation en K évite une dilution en K des tissus, ce qui arrive souvent avec un apport important d'azote.Un essai à 13 semaines sur un sol pour essais biologiques, extrait d'une station boréale, a montré que la croissance et l'allocation des nutriments étaient significativement augmentées par de grandes réserves d'azote accumulé après des apports intensifs de nutriments.Environ 72 à 80 % de N requis pour la croissance des nouvelles pousses provenaient du cycle interne, démontrant l'importance des apports pour augmenter les retranslocations.Un apport intermédiaire (24 mg N) était plus efficace pour promouvoir l'accumulation de N et la croissance des deux types de semis.La survie a été réduite (30 %) seulement pour la plus forte dose.Les résultats de cette étude ont démontré l'avantage potentiel de ces pratiques pour l'amélioration de la croissance des semis dans les stations forestières du Nord. Picea mariana / période d'endurcissement / azote / apport de nutriment / retranslocation / super apport
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".