668 FUNDAMENTALS OF FRUIT PRODUCTION 



existing between them. No better evidence to this effect is needed than 

 some of the facts brought out by the analyses of the Florida and Hawaiian 

 pineapple soils that have been mentioned. Certainly it would not be 

 suspected from these analyses that in the Hawaiian soils with their 20 to 

 35 per cent, of iron (indeed there is one local pineapple district in the 

 Hawaiian Islands where the soil contains 85 per cent, iron and titanium ^^) 

 the plants often show symptoms of iron starvation and that iron sulphate 

 is their most valuable fertilizer, though less than three-tenths of 1 percent, 

 of iron furnishes an ample supply in the Florida sands. The relationship 

 between soil and crop is more than that existing between the different 

 factors in a problem in addition and subtraction. Other aspects of this 

 general question are discussed in the sections on Water Relations and 

 Nutrition. 



VEGETATION AS AN INDEX TO CROP ADAPTATION 



Though at present no single feature of the chemical or mechanical 

 composition of the soil can be designated the chief cause for the way 

 some fruit crops grow on it, soil differences, even slight differences, may 

 be of great significance to the fruit grower. His study of soils should 

 include more than the features brought into contrast by chemical and 

 mechanical analyses. The types of the native vegetation may serve as 

 very useful indices of probable productivity when planted to cultivated 

 crop plants belonging to the same or a closely related genus or family; 

 knowledge of plant ecology may make it possible to predict with accuracy 

 the way some entirely unrelated plant will behave on the soil in question. 

 For instance, in Ohio, land upon which the sugar maple, beech, oak, or 

 chestnut thrive naturally is hkely to be well suited to the apple, but land on 

 which the elm is native is seldom desirable for that fruit. ^^ In western 

 Oregon and western Washington, hill land supporting a vigorous growth 

 of the native "brake" or fern (Pteridium aquilinuvi pubescens) is charac- 

 teristically good for prunes. In the Ozarks "post-oak" land is good for 

 grape culture. Ney^^ has pointed out that the kinds of forest trees grow- 

 ing on land often form something of an index of its chemical condition. 

 He says, "As regards the chemical composition of the soil, even slightly 

 sour marshy soils are unfavorable to all species of trees except alder, 

 birch, and spruce ; whilst sour soils, liable to dry up at certain seasons, 

 are unsuited to all except birch, spruce, Scots and Weymouth pines." 

 Ash, maple, sycamore, and elm require a moderate quantity of lime and 

 beech, hornbeam, oak, as also larch and Austrian pine, thrive best on soils 

 that have at least some lime in their composition. The hardwoods— oak, 

 ash, maple, sycamore, elm, chestnut, beech and hornbeam — also appear 

 to demand the presence of a considerable quantity of potash, while on the 

 other hand, spruce, silver fir and especially Scotch pine and birch thrive 



