ORCHARD SOILS 



667 



Evidence on Soil Requirements from Fertilizer Ex-periments. — Point 

 is lent the last statement by data presented in Table 23 assembled 

 by Stewart, showing the response to fertilizer applications of trees growing 

 in soils of varying productivity. In commenting on these data Stewart^^ 

 remarks: "These figures show that the correlation between soil composi- 

 tion, as determined by the methods of soil sampling and analysis above 

 specified, and the actual response of the associated trees to additional 

 fertilization is either exceedingly slight or absent entirely. One would 

 naturally expect that the largest response would appear where the chem- 

 ical fertility of the soil was lowest, and vice versa. This evidently has not 

 occurred. In fact, the least response to practically all types of fertiliza- 



1 Complete fertilizer. 2 Manure. ^ pgr cent, increase in growth, instead of yield. 



tion has occurred in the soil analyzing poorest of all, and some of the largest 

 responses have appeared in the chemically richest soils. The ordinary 

 methods of soil analysis are not yet adequate to furnish a reliable indi- 

 cation of the fertility needs of an orchard. Trees on chemically rich 

 soils will not of necessity prove unresponsive to additional fertilization, 

 nor will trees on chemically poor soils always prove responsive. In other 

 words, some other indicator than the chemical composition of the soil, 

 as here determined, must be relied upon to determine the real need of 

 additional fertility in an orchard. At present, therefore, the surest and 

 most delicate test yet devised for determining the fertility needs of an 

 orchard soil is the actual response of the living tree in the soil concerned 

 to appropriate fertility additions." 



The soil is a very complex substance and the soil solution likewise; 

 apparently absolute amounts of certain elements or compounds that it 

 contains are not so important as the state of balance or equilibrium 



