352 



SOILS. 



soils as those of Florida, mentioned below ; the probability be- 

 ing that where lime is naturally deficient, the effects of dilu- 

 tion will be much more pronounced in diminishing production, 

 because of the absence of the previous favorable action of lime 

 upon the availability of the soil-ingredients. 



Lowest Limit of Plant-food Percentages and Productive- 

 ness found in Virgin Soils. The subjoined table shows some 

 of the very low plant-food percentages found in natural soils, 

 all being of a sandy character : 



The average of plant-food percentages in all these soils is 

 quite ]<>\v, and at first sight there seems to be little choice be- 

 tween them. Vet two of them X< >s. nS and SS. fr, mi Missis- 

 sippi are n*.t only quite productive at the outset, but also 

 fairly durable. This becomes measurably intelligible when it 

 is known that both are of great depth, and SO well drained that 

 roots can descend for many feet; while the o imposition of the 

 soil-material is almost identical for three or four feet. On the 

 other hand, both Nos. 206 and _M4 are quite shallow, being un- 

 derlaid by sand almost devoid of plant-food at about two feet. 

 In addition, both have extremely low percentages of phos- 

 phoric acid ; while the rest show near .io r /f of that ingredient, 

 an amount which, as will be seen hereafter, is considerably 



