24 AMERICAN AGRICULTURE. 



confessed his practice, gave some apparently strong confirma- 

 tions of his theory. By carrying tillage far below the surface, 

 thus securing the minute division of the earth, and render, 

 ing it permeable to the roots, he insured the free access of air 

 and moisture, which are among the first and most important 

 requisites in the growth of vegetables. 



But Tull wrote before agriculture became a science, and 

 omitted to estimate the large amount of fertile ingredients 

 which every crop takes out of the soil, and which can only be 

 supplied by the addition of fresh materials. A succession of 

 crops would therefore, so far reduce the soil as to render it 

 necessary to add manures, or vegetation must inevitably fail. 

 This careful laborious practice could only for the time being, 

 enhance the crop and prolong its available supplies; yet in 

 accomplishing even this object, his example is worthy of the 

 imitation of every tiller of the soil. 



FRIABLENESS OF THE SOIL, is a quality equally removed 

 from the adhesiveness of strong clay, or the openness of loose 

 sand. Good loams, and fertile alluvial soils, always possess 

 this property. When stirred by the plow, the spade, or the 

 hoe, the earth should fall and crumble readily, although wet. 

 Such a condition secures a ready admission to the roots, which 

 thus easily pervade the soil, and draw from it in every direc- 

 tion, their necessary support. Under draining and the 

 addition of coarse manures to clay, fermented manures and 

 ashes to sand, and lime and gypsum to both, will materially 

 enhance their friableness. 



Color is an essential feature in soils, and like friableness, 

 it has an important relation to their capacity for heat and 

 moisture. Dark colored earths, and black in the highest 

 degree, absorb heat more rapidly than any other when exposed 

 to a temperature above their own, and it escapes with equal 

 readiness when their relative temperatere is reversed. 



A rough pulverised surface, which is seen in the minute 

 inequalities of a friable soil, produces the same result. 

 During the heat of the day, especially when the sun's rays 

 fall upon the earth, the dark friable soil imbibes the heat free- 

 ly, and transmits it to the remotest roots, thus securing warmth 

 to the plant, which is one of the necessary conditions of its 

 growth. When the temperature of the air falls, on the 

 approach of evening, a reversed action in the soil takes place 

 by which the heat as rapidly escapes. This immediately 

 brings the surface to "the dew point" and secures a copious 



