142 THE SOILS OF ST. MAEY's COUNTY 



Miocene marl beds underlying all of the upland portion of the county 

 and reaching the surface in nearly every clitt' and stream cutting over 

 the upper half of the region. This lime supply consists of the calcareous 

 tests of marine shellfish which once lived upon the sea bottom when 

 the ocean covered the county. The shells, buried in sand and elevated 

 above water level, can be dug out by the wagonload and converted into 

 excellent lime by sieving out the sand and burning the remaining shells, 

 just as lime rock is burned to lime. The sifting would be imnecessary 

 in the case of some of the deposits, since the small amount of sand present 

 would be a benefit to the heavier types of land. The Leonardtown loam 

 would benefit materially from such liming, except, of course, when tobacco 

 is to be raised. 



Tlie plowing under of gTeen crops, especially the leguminous plants 

 of the clover and cowpea varieties, furnishes another method of enrich- 

 ment highly desirable on almost all the soil types of St. Mary's County, 

 and does not present the difficulties of liming, since this kind of fertilizer 

 is of great benefit to the tobacco crop. These leguminous crops furnish 

 a fair forage for cattle during a period of their growth, and if allowed 

 to continue growing they produce a mass of organic matter for incor- 

 poration with the soil; and all the time, beneath the surface of the 

 ground, certain minute bacteria, living on the roots, are taking nitrogen 

 from the air and storing it in the soil, thus helping its enrichment. 



The ordinary practice of putting from 200 to 400 pounds of commercial 

 fertilizer, costing from $18 to $40 per ton, upon the farms of St. Mary's 

 County has a double efEect. It produces the crop, but it also enters a 

 large item on the expense side of the farm account, and on some soils 

 its continued use has the effect of burning out the soil, so that periods 

 of fallowing become essential. For certain crops special fertilizers will 

 always be necessary, and commercial fertilizers are to be commended 

 highly, but in St. Mary's County on all soils the use of stable manure 

 and the plowing under of green crops are to be preferred, while on 

 the soils least suited to tobacco the abandonment of that crop and the 

 free use of lime in conjunction with organic matter have already 

 become necessar^y, as is shown by the forest areas given over to nature's 

 cultivation. 



