Late-season fertilization of Picea mariana seedlings: intensive loading and outplanting response on greenhouse bioassays

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 e...

The expression of GintPT, the phosphate transporter of Rhizophagus irregularis, depends on the symbiotic status and phosphate availability

“…However, we do not know whether plants take up more Pi for their needs or whether this is an example of the so-called luxury consumption phenomenon, previously described for a wide array of vascular plants (Lawrence 2001;Tripler et al 2002;Boivin et al 2004;Sharma and Sahi 2005;Sharda and Koide 2010), in which plants acquire Pi resources beyond their requirement levels and then store them. This also suggests that the low Pi level is not only perceived by the host as a starvation condition, but also by the fungus, provoking a sort of competition for Pi uptake between the two symbionts inside the arbusculated cells.…”

Characterizing fertility targets and multi-element interactions in nursery culture ofQuercus rubraseedlings

“…4B) occurred when a decline in K concentration (21%) reduced growth and K uptake (56%). The greater N accumulation in shoots may partly explain K reduction at higher dose rates because increased NH 4 + uptake has been found to reduce K uptake [4,49]. Higher K supplementation can be used to correct K dilution [5,49].…”

“…Extra high fertilization or nutrient loading (l) induces luxury uptake in excess of growth demand, which are stored as reserves for later utilization. Excess fertilization (e) may induce toxicity signified by diminished plant growth and N content at increasing tissue N concentration (adapted from [38] 4 -N (1.20%), NO 3 -N (11.75%) and urea-N (2.05%). Supplemental irrigation was supplied twice weekly at similar rates by periodic weighing of pots to determine amount of water to be added to return pots to container capacity [47,51] to avoid potential confounding effects of irrigation on treatment responses.…”

Fall fertilization of Pinus resinosa seedlings: nutrient uptake, cold hardiness, and morphological development

“…This can be averted by applying fertilizer at a higher rate or exponentially (Boivin et al, 2004). Fall fertilization may significantly increase foliar nitrogen (N) levels (Boivin et al, 2004;van den Driessche, 1985van den Driessche, , 1988, enhance root growth potential (van den Driessche, 1988), promote earlier bud break (Margolis and Waring, 1986;Thompson, 1983;van den Driessche, 1985), and improve survival and growth compared to conventionally fertilized seedlings (van den Driessche, 1988).…”

“…BSP.) (Boivin et al, 2004), loblolly pine (Pinus taeda L.) (Sung et al, 1997;VanderSchaaf and McNabb, 2004), slash pine (Pinus elliottii var. elliottii [Engelm.])…”