THE PORTERS LOAM AND PORTERS BLACK LOAM. 9 



The adoption of these methods for the prevention of erosion would 

 considerably increase the extent of the area capable of cultivation in 

 the case of the Porters loam, and would somewhat extend it even in 

 the case of the Porters black loam. In addition to these methods of 

 the control of soil erosion there should be added a systematic 

 rotation of crops, which will permit the soils to remain under grass 

 cover for a considerable period during each rotation. The fact that 

 timothy, bluegrass, and the clovers all grow to advantage upon both 

 types of soil renders this an easy as well as an efficient method for 

 the reduction of the ravages of soil-washing. 



The restoration of organic matter to the surface soil in the case of 

 the Porters loam has been mentioned as one of the essential steps 

 toward the prevention of soil erosion. It is also necessary in order 

 to form a complete, easily tilled surface soil, which will be suffi- 

 ciently retentive of moisture to maintain a good growth of the grain 

 crops, particularly of corn, during the summer season. For such 

 purposes the growing of cowpeas, seeded between the rows of corn at 

 the last cultivation, should be practiced at the lower altitudes where 

 the type is found. Crimson clover would also be a valuable crop for 

 seeding with the corn under the same conditions. At the higher 

 altitudes the restoration of organic matter to the soil, because of 

 climatic conditions, must be dependent upon the growing of winter 

 cover crops such as rye and winter wheat, and upon the turning under 

 of the sod from grass, which should be grown in regular rotation 

 with other crops. In addition, an occasional crop of buckwheat grown 

 solely for this purpose might be turned under upon areas where both 

 the mineral matter and the organic matter of the surface soil have 

 been bodily removed by erosion. In general the Porters black loam is 

 sufficiently supplied with organic matter, so that these practices 

 are not essential upon that type. 



LIMITATIONS UPON SPECIAL CROPS. 



The chief limitation upon the production of both general and 

 special farm crops within the area occupied by the Porters loam and 

 Porters black loam, aside from those limitations of use already men- 

 tioned, consists in the climatic variations dependent upon the wide 

 differences in altitude occupied by these two types. Since the chief 

 special crop produced within the area is the apple crop, and since this 

 is largely confined to the Porters black loam, the climatic limitations 

 which circumscribe the growing of this crop are illustrative of the 

 effect of climate upon the agriculture of the region. 



For successful fruit growing by far the best orchard location is 

 within the " frostless belt " or " thermal zone," the altitude of 

 which varies considerably in the different locations from Virginia 

 1240 Cir. 3011 2 



