SOIL PREPARATION 83 
purpose. One of the best tools for greenhouse work is 
the smallest-sized smoothing harrow (Fig. 28) with a 
second leveling board adjusted behind the last row of 
disks. When it is desired to use the plow, the Icttuce 
should be planted in long, narrow strips, so that when the 
successional crops of lettuce are harvested the strips can 
be plowed, harrowed and replanted with the minimum 
loss of time. When horse implements are used (Fig. 26), 
some hand work will be required along the sides and ends 
of the houses, to secure a finished appearance. 
Spading and raking.—In the smaller houses and in 
most of the large establishments the soil is prepared by 
the use of the spade and rake. Spading forks are often 
used instead of spading shovels. Whatever the method 
Fig. 28.—Small smoothing harrow. 
employed, the soil should be left in a fine state of division. 
Applying lime.—The various commercial forms may 
be used for the treatment of greenhouse soils. While 
ground stone lime is most convenient to apply, unslaked 
stone lime and hydrated lime are used more generally 
than other forms. Stone lime is simply deposited in 
small piles in the greenhouses and sufficient water 
applied to it with a hose to cause prompt slaking, and the 
lime is then spread with a shovel. There is no better 
time to apply lime than after plowing or spading and 
before harrowing or raking. It should not be mixed 
directly with manure because it will release the ammonia. 
No experiments have been conducted to determine the 
