Editing Conifer (section)

==Conditions for growth==

Conifers [[Plant nutrition |can absorb nitrogen]] in either the [[ammonium]] (NH<sub>4</sub><sup>+</sup>) or [[nitrate]] (NO<sub>3</sub><sup>−</sup>) form, but the forms are not physiologically equivalent. Form of nitrogen affected both the total amount and relative composition of the soluble nitrogen in white spruce tissues (Durzan and Steward).<ref name="Durzan-1967">{{cite journal |last1=Durzan |first1=D.J. |last2=Steward |first2=F.C. |year=1967 |title=The nitrogen metabolism of ''Picea glauca'' (Moench) Voss and ''Pinus banksiana'' Lamb. as influenced by mineral nutrition |journal=Can. J. Bot. |volume=45 |issue=5  |pages=695–710 |doi=10.1139/b67-077  |bibcode=1967CaJB...45..695D }}</ref> Ammonium nitrogen was shown to foster [[arginine]] and [[amide]]s and lead to a large increase of free [[guanidine]] compounds, whereas in leaves nourished by nitrate as the sole source of nitrogen guanidine compounds were less prominent. Durzan and Steward noted that their results, drawn from determinations made in late summer, did not rule out the occurrence of different interim responses at other times of the year. Ammonium nitrogen produced significantly heavier (dry weight) seedlings with a higher nitrogen content after 5 weeks<ref name="McFee-1968">{{cite journal |last1=McFee |first1=W.W. |last2=Stone |first2=E.L. |year=1968 |title=Ammonium and nitrate as nitrogen sources for ''Pinus radiata ''and ''Picea glauca'' |journal=Soil Sci. Soc. Am. Proc. |volume=32 |issue=6 |pages=879–884 |doi=10.2136/sssaj1968.03615995003200060045x  |bibcode=1968SSASJ..32..879M }}</ref> than did the same amount of nitrate nitrogen. Swan  found the same effect in 105-day-old white spruce.<ref name="Swan-1960">{{cite report |last=Swan |first=H.S.D. |year=1960 |title=The mineral nutrition of Canadian pulpwood species. 1. The influence of nitrogen, phosphorus, potassium, and magnesium deficiencies on the growth and development of white spruce, black spruce, jack pine, and western hemlock seedlings grown in a controlled environment |publisher=Pulp Paper Res. Instit. Can. |location=Montreal QC |series=Woodlands Res. Index Number 116 |id=Tech. Rep. 168}}</ref>

The general short-term effect of nitrogen fertilization on coniferous seedlings is to stimulate shoot growth more so than root growth (Armson and Carman 1961).<ref name="Armson-1961">{{cite book |last1=Armson |first1=KA |last2=Carman |first2=RD |year=1961 |title=Forest tree nursery soil management |publisher=Ont. Dep. Lands & Forests, Timber Branch |location=Ottawa ON}}</ref> Over a longer period, root growth is also stimulated. Many [[Plant nursery |nursery]] managers were long reluctant to apply nitrogenous [[fertilizer]]s late in the growing season, for fear of increased danger of frost damage to succulent tissues. A presentation at the North American Forest Tree Nursery Soils Workshop at Syracuse in 1980 provided strong contrary evidence: Bob Eastman, President of the Western Maine Forest Nursery Co. stated that for 15 years he has been successful in avoiding winter "burn" to [[Picea abies |Norway spruce]] and white spruce in his nursery operation by fertilizing with 50–80&nbsp;lb/ac (56–90&nbsp;kg/ha) nitrogen in September, whereas previously winter burn had been experienced annually, often severely. Eastman also stated that the overwintering storage capacity of stock thus treated was much improved.<ref name="Eastman-1980">{{cite conference |last=Eastman |first=B |title=The Western Maine Forest Nursery Company |pages=291–295 |book-title=Proc. of the North American Forest Tree Nursery Soils Workshop |date=July 28 – August 1, 1980 |location=Syracuse, New York |publisher=Environment Canada, Canadian Forestry Service, USDA For. Serv.}}</ref>

The concentrations of nutrients in plant tissues depend on many factors, including growing conditions. Interpretation of concentrations determined by analysis is easy only when a nutrient occurs in excessively low or occasionally excessively high concentration. Values are influenced by environmental factors and interactions among the 16 nutrient elements known to be essential to plants, 13 of which are obtained from the soil, including [[nitrogen]], [[phosphorus]], [[potassium]], [[calcium]], [[magnesium]], and [[sulfur]], all used in relatively large amounts.<ref name="Buckman-1969">{{cite book |last1=Buckman |first1=H.O. |last2=Brady |first2=N.C. |year=1969 |title=The Nature and Properties of Soils |edition=7th |publisher=Macmillan |location=New York}}</ref>