Soil acidity as affecting germination, growth, and development of plants has received considerable attention in recent years. · These studies have dealt with many phases of the problem, from the effect of hydrogen and hydroxyl ions on the growth of plants to the indirect effect of the concentration of these ions on the toxicity of or deficiency of certain elements. The influence of soil acidity has been ascribed to several causes, the most important of which are effect on supply of available calcium needed by plants in the manufacture of plant foods, influence on the symbiotic nitrogen-fixing bacteria, toxic or destructive effect on root tissues, and prevention of plants from getting at a sufficiently rapid rate the calcium needed to precipitate acids formed in them.
REVIEW OF LITERATUREComparatively little work has been done to determine the effect of hydrogen-ion concentration on seed germination and the growth and development of forest tree seedlings. What literature is available indicates that soil acidity may be a limiting factor in forest tree nursery work and in the establishment of seedlings in the forest. Baldwin (7 ) 3 found that Norway spruce (Picea ex~elsa) seed apparently germinated better in soils having a higher hydrogen-ion con-. centration than in more alkaline soils. Tourney and Li (8) found that
Forest tree nurseries, due to limited area and intensity of management, are compelled to use fertilizers in some form if the quality of stock is to be maintained. Tree seedlings in no way differ from field crops in their dependence on the soil for plant food. Coniferous species undoubtedly demand different elements, while a much greater difference might be expected between conifers and hardwoods. The r6le of fertilizers is to increase growth and quality, whether it is brought about by an ameliorating effect upon the soil or by directly supplying the essential plant nutrients in available form.Following the lead of agronomists, foresters and nurserymen have experimented with various kinds of fertilizers and with varying results. Much of the information available is very general and some of it contradictory: Preference today is for green manures, such as oats, rye, cowpeas, buckwheat, etc., or composted woods litter and soil, with combinations of these and the occasional addition of commercial fertilizers. The addition of humus to most nursery soils proves beneficial and, when space allows, green manuring is undoubtedly an excellent practice. The use of commercial fertilizers alone in most forest tree nurseries has met with indifferent success. This may be due to sev8ral causes, the principal one being rapid loss of fertilizer by leaching, as in sandy soils or soils deficient in other elements than those applied.
REVIEW OF LITERATUREDefinite data on results of fertilizing coniferous seedbeds, such as weight and length of top and roots of seedlings; length, number, and size of rootlets; soil analysis, especially pH reaction; and amount and analysis of fertilizer used are available in only a few instances and then not complete.Hansen (5), 3 in a study of the effect of five different chemical fertilizers on the growth of white and red pine seedlings, found that neither species showed a preference for any one element. His check plat, on which no fertilizer had been applied, was among the best. He con-
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.