148 



SOIL CONDITIONS AND PLANT GROWTH 



TABLE LIX. MECHANICAL ANALYSES OF SOILS WELL SUITED TO CERTAIN CROPS IN 

 THE SOUTH-EASTERN COUNTIES; LIMITS OF VARIATION. HALL AND RUSSELL (1230). 



Low amounts of clay and fine silt, and high amounts of coarse 

 sand whenever the clay begins to approach 1 2 per cent, characterise 

 the potato soils ; these are the most porous of the series, allowing free 

 drainage and aeration. Barley soils on the whole are heavier and 

 other analyses show they may be much shallower. Fruit and hops 

 both require deep soils, and only seem to find their most favourable 

 circumstances in a restricted class of soils : the fruit soils generally 

 contain rather more sand and less silt than the hop soils. But the 

 fruits differ among themselves ; the best nursery stock is raised on soils 

 of the potato class, where the conditions are for some unknown reason 

 very favourable to fibrous root development ; strawberries prefer the 

 lighter and apples the heavier kinds of fruit soil. Even different 

 varieties of the same plant show distinct preferences for one class of 

 soil over another : the finest varieties of hops are found only on the 

 typical hop soils, and have to be replaced by coarser varieties directly 

 it is desired to grow hops on heavier soils. Preferences for certain 

 soil conditions are also shown by varieties of the common crops, oats, 

 barley, wheat, etc. ; unfortunately these can only be discovered by 

 direct field trials, and even then the results only hold so long as 

 similar conditions prevail and may often be reversed in a different 

 climate or season. 



Still more subtle differences may be observed : one and the same 

 variety of a crop will acquire one habit of growth on one soil and a 

 different habit on another. Wheat growing under the best soil 

 conditions will produce stiff straw and ears well set with corn, so that 

 a crop of fifty or sixty bushels per acre may be raised without diffi- 

 culty ; on soil rather different in type, and especially under somewhat 

 different climatic conditions, only thirty or forty bushels can be raised, 

 because the ears are less thickly set and the straw is too weak to 

 carry a heavier crop, becoming " laid " directly an attempt is made to 

 increase production by increased manuring. 1 Whether some unknown 



1 Further illustrations are given by the author in Science Progress, 1910, v., 286. 



