SOILS. 



27 



luxuriant crops, without the aid of manures ; and it must be 

 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 to a great 

 depth, and rendering 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 v ege- 

 tables. 



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 

 imitation by 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 loam, and fertile, alluvial soils always possess 

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

 hoe, the earth ought to fall and crumble readily, although 

 it should be wet. Such a condition secures a ready admis- 

 sion to the roots, which thus easily pervade the soil, and 

 draw their necessary support from it in every direction. 

 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 temperature is reversed. 



A rough pulverised surface, which is seen in the minute 

 inequalities of a friable and well cultivated soil, produces 

 the same result. During the heat of the day, and especially 

 when the sun's rays fall upon the earth, the dark, friable soil 

 imbibes the heat freely, and transmits it to the remotest roots ; 

 thus securing that 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. 



