250 SEEDING AND PLANTING 



and spray; now, however, the beds of larger trees are irrigated by 

 flooding and the seedbeds are usually flooded before the seeds 

 germinate. 



23. THE FERTILITY OF NURSERY SOIL: MANURING 



Large amounts of potash, phosphorus, nitrogen, and other 

 chemical elements in compounds available as plant nutrients are 

 taken yearly from the soil by growing nursery stock. Nothing is 

 returned to the soil as the trees are removed root and branch. A 

 rapid deterioration of the soil takes place unless its fertility is 

 maintained by the liberal application of fertilizers. Nursery 

 stock can be successfully grown for a period of several years on 

 exceptionally good soils without manuring, but sooner or later 

 the application of fertilizer becomes necessary. 



On rich, sandy loams and other soils having a high degree of 

 fertility, the decrease in productivity due to successive cropping is 

 often very slow. As a rule, fertilizers should not be applied until 

 the appearance of the crop clearly shows their need. Experi- 

 ments conducted at the Wind River nursery indicate that a heavy 

 dressing of well-composted manure worked into the surface soil of 

 the seedbed had the effect of stimulating top growth far more 

 than root growth. It also had the effect of producing irregular- 

 sized plants and retarding the formation of winter buds. These 

 unfavorable results more than overbalance the increase in average 

 size due to fertilizing. 



The application of the plant nutrients that are deficient in the 

 soil, without regard to their effect upon its physical condition, 

 will seldom suffice. Special attention should always be given to 

 maintaining an adequate supply of humus. As the nursery stock 

 leaves nothing on the ground to decay and form humus, soiling 

 crops and stable manure are usually preferable to concentrated 

 or commercial fertilizers when used alone. 1 



Whether a vegetable, animal, or mineral fertilizer alone or in 

 mixture will give the best results at least cost depends upon local 

 conditions as well as upon the physical and chemical characteris- 

 tics of the soil. Fertilizers are most effective when applied in the 

 form of fertilized soil or compost. Thereby the danger of excessive 



1 Mayr, Heinrich: Waldbau auf naturgesetzlicher Grundlage. S. 410. 

 Berlin, 1909. 



