1 20 TILLA GEMO VEMENT$ OF SOIL WA TER [chap. 



evaporation from the firm surface. Thus a tool like the 

 old broadsharing plough, still used on the chalk, is par- 

 ticularly valuable in preparing a tilth for roots, for, while 

 creating a loose surface tilth, it is consolidating the soil 

 below and increasing its power of lifting water from the 

 subsoil. 



Similarly, in the semi - arid regions of Western 

 America and in Australia, where the rainfall is barely 

 sufficient for the needs of the crop, in the preparation of 

 the land great importance is laid on the two operations 

 of " subsoil packing" and "the establishment of a soil 

 mulch." This is the equivalent of the English practice of 

 preparing a seed bed for roots ; frequent cultivation with- 

 out inverting the soil in order to work it down to a fine 

 tilth, constant use of the ring roller or subsoil packer to 

 consolidate this crumb until it will lift water by capillarity, 

 and, finally, the production and continual renewal by 

 means of light cultivators or horse hoes of a very thin 

 skin of loose soil on the surface. 



Valuable as the operation of rolling is on grass 

 land in the early spring, in order to consolidate the soil 

 round the roots of the grass after the surface has been 

 lifted by the winter frosts and by the action of worms, 

 it should be borne in mind that it is easy to do harm 

 by injudicious rolling in wet weather on soils that are 

 at all heavy. Even on grass land the clay may become 

 so puddled or tempered that it dries round the roots 

 with a very harsh caked surface, little permeable to 

 air and water. This sort of damage is perhaps most 

 often seen on lawns and cricket grounds which are 

 rolled repeatedly with heavy rollers when the ground 

 is thoroughly wet ; a smooth, pasty surface is pro- 

 duced to the ultimate great detriment of the growth 

 of the grass. Of course upon arable land the greatest 

 care must be taken never to roll when the top is at all 



