The Care of Growing Crops 201 
supply of water from below is cut off. This dry surface 
layer then covers the soil below like a heavy cloth 
spread on the ground. 
Beneath a good surface mulch of dry soil the earth 
is moist, even after long periods of dry weather; and 
when a soil in good physical condition (see page 58) is 
kept moist in this way it remains loose so that the roots 
can easily penetrate it. Thus the mulch not only saves 
the water for the plants, but it keeps the soil in good 
physical condition for the roots. 
When to cultivate. Rainfall and surface irrigation 
destroy a surface mulch. Hence the garden should be 
cultivated soon after each rain or irrigation. If one 
waits several days, a dry crust will form and the surface 
will become cracked and broken up into coarse lumps. 
Much water is lost in this way; also such a soil is in poor 
condition for the roots. 
Shallow cultivation should begin as soon as the seed- 
lings are above the ground, and if seeds are slow in 
germinating, as are parsnips and carrots, the soil should 
be stirred before the plants are up. Crops need more 
careful and more frequent cultivation while they are 
young than they do later, for the roots are nearer the 
surface and the soil is less shaded; hence the roots are 
more exposed to the drying effects of the sun and air. 
In cultivating young crops, work the rake or tool 
used in such a way that fine loose dirt is thrown about 
the base of seedlings or even over seedlings that are not 
yet above ground. Cultivate after each rain as soon as 
the soil is dry enough not to stick to the tools. Do not 
draw the cultivating tools so close to plants that the main 
