THE FOREST NURSERY 251 



application is not likely to occur and they are brought to the 

 young trees in their most useful form. 



Extensive researches and experiments conducted in Europe by 

 Heck, Grundner, Kienitz, Engler, Swappach, Moller, Reuss, and 

 others prove the necessity for the liberal use of fertilizers in per- 

 manent nurseries. Recent investigations of Pettis, 1 Bates, 2 and 

 others in the United States show favorable results from the appli- 

 cation of farm manures and various commercial fertilizers. Ex- 

 periments conducted by the author at New Haven on sandy loam 

 from 1900 to 1908 show that two successive crops of 2-year white 

 pine seedlings are as many as can be grown without applying 

 fertilizers, as there is a marked falling off in size and quality, 

 due entirely to soil exhaustion, particularly the absence of humus. 



As fertilizers not only add useful plant nutrients to the soil but 

 also improve its physical condition, sand added to a clay or other 

 heavy soil, by improving its consistency and causing better plant 

 growth, is a fertilizer. The application of stable manure or 

 other well-rotted organic material to an overlight soil or a very 

 heavy soil is particularly useful in improving its physical con- 

 dition. It renders overlight soils less permeable and heavy soils 

 more permeable to both air and water. 



The materials which are brought into the soil by manuring 

 and which directly supply a deficiency in plant nutrients are for 

 the most part phosphates, potash salts, and nitrates or materials 

 which become converted into these in the soil. Lime, magnesia, 

 and sulphur in various forms can occasionally be applied to ad- 

 vantage. The sole purpose of fertilizers is to increase growth and 

 quality, whether it be brought about by their ameliorating effect upon 

 the soil or by directly supplying the essential plant nutrients in 

 available form. 



24. Classification of Fertilizers Used in Nursery Practice. 

 Although all kinds of materials that are useful in improving the 

 fertility of soil may be used in nursery practice when properly 

 applied, those most acceptable may be classed as follows: 



a. Fertilizers of vegetable origin, such as leaves, moss, weeds, 

 and other similar material ; also soiling plants, such as the cowpea, 



1 Pettis, C. R.: New York forest, fish and game commission. Twelfth 

 annual report, p. 29. Albany, 1907. 



2 Bates, C. G. and Pierce, R. G.: Forestation of the sand hills of Nebraska 

 and Kansas. (U. S. Forest Service, Bui. 121. 1913.) 



