114 PRINCIPLES OF TILLAGE. 



culture of drilled and hoed crops, the surface soil should 

 be kept clean while the crop is growing, for the same rea- 

 son that the soil is required to be made so before depos- 

 iting the seed ; viz. , to facilitate the decomposition of the 

 vegetable food, to stimulate the organs of the plants, and 

 increase the growth and product of the crop. There is 

 no better expedient for preventing the evils of drought 

 upon a soil, than that of keeping the surface mellow and 

 clean. Atmospheric air and dew, always charged with 

 the food of plants, penetrate such a surface as into a 

 sponge, and impart to the roots of plants both aliment 

 and stimuli. Dews fall upon a hard surface, and are 

 evaporated by the first rays of the morning sun ; but they 

 penetrate a loose surface, and moisten and fructify it. 

 Hence the high repute of drill husbandry, which enables 

 the cultivator to keep his crops clean, and the surface of 

 his soil mellow and open. 



Good tillage has reference to depth, as well as quality 

 of tilth. " There are many plants, the roots of which 

 are found from fifteen to twenty, and even thirty feet un- 

 der ground — sainfoin and lucerne, for instance ; even red 

 clover will strike down three feet if the soil be a fertile 

 loam ; and some of our commonest vegetables, if it be a 

 friable or sandy, push their tap roots to about the same 

 depth. The roots of wheat will penetrate as far as eight 

 inches into the earth ; and when sown on the crowns of 

 ridges, they have been found at the depth of twelve. We 

 may therefore assume the depth of twelve inches as the 

 utmost vegetative Hmit of corn land. Provided the soil 

 be open and fertile, the nearer its depth approaches to 

 tw^elve inches, the greater number of plants may it there- 

 fore be supposed capable of furnishing with support." — 

 British Husbandry, vol. ii. pp. 49, 50. 



nSoils should be ploughed as deep as the substratum 

 will admit, at least once in a course of crops, if this can 

 be reached with the force of an ordinary team ; and when 

 the surface soil is superficial, it should be deepened, as 

 fast as fertility can be imparted, by turning up, at suitable 

 intervals, some portion of the subsoil. The atmosphere 



