658 FUNDAMENTALS OF FRUIT PRODUCTION 



doing fairly well in soils ranging from almost pure sand to heavy clay, 

 but it does its best only in those that are fairly heavy and well drained; 

 however, it will endure a wet, poorly aerated soil much better than 

 most fruit plants. ^^ Probably nowhere in the world does the pineapple 

 do better than along the east coast of Florida, between Fort Pierce and 

 Lake Worth, where the soil is almost a pure white sand (containing 

 actually upwards of 98 per cent sand, gravel and silt);^^ nevertheless 

 they are grown very successfully on some of the heavy soils of the Hawa- 

 iian Islands. It is generally recognized, however, that the soil that 

 may be best for a particular fruit or some particular variety in one sec- 

 tion may not be best in another section with different chmate and distinct 

 environmental conditions. Thus in New York the Concord grape 

 grows on a wide variety of soils but seems to prefer a fairly strong loam 

 with considerable clay; in western Washington the same variety can 

 be grown successfully only in hght sandy or sandy loam soils that tend 

 to hasten maturity of fruit and vine. In general, the more favorable 

 the texture of the soil for both the lateral and vertical development of 

 the root system, the better. 



Requirements as to Depth. — Theoretically, a soil need be only half 

 as rich as another in order to support equally well a certain amount 

 of vegetative growth if it is of such a character that roots penetrate 

 twice as deep. Furthermore, since water is a limiting factor as often 

 as plant nutrients, a tree with the deeper root system, though in poorer 

 soil, is really in a better position than one growing in a richer, but shal- 

 lower, medium. Only under very special conditions should ordinary 

 deciduous tree fruits be planted in a soil in which the roots cannot pene- 

 trate freely to a depth of 2}-^ to 3 feet in humid regions and to a depth of 5 

 to 10 feet in arid and semi-arid regions; soils that will permit greater pene- 

 tration are preferable. Shallowness of soil, hardpan or plowsole close to 

 the surface, impervious subsoil and poor drainage are interrelated factors 

 which check vegetative growth, reduce yields and the size, quality and 

 grade of the fruit, favor irregular bearing and lead to numerous physio- 

 logical troubles, the treatment of which is difficult. 



Classification of Soils According to Size of Soil Particles. — Since 

 there is occasion repeatedly to refer to soils of different physical structure, 

 a classification based on mechanical analysis, as used by the Bureau 

 of Soils of the Federal Department of Agriculture, is presented here^* 

 (see Table 15). 



It should be noted in connection with this classification that no 

 account is taken of gravel or stones above 2 millimeters in diameter. 

 Many soils contain rock particles larger than this maximum and not 

 infrequently these constitute a large proportion of the soil volume. 

 Accordingly a soil that in this scheme would be classified as a silt or even 

 a clay might in fact be gravelly or rocky or stony in character. Though 



