CROP TREATMENT 227 
Ordinarily, however, after fall sowing there is no 
further need of treatment until the following spring. 
The spring treatment is of considerably more im- 
portance, for when the warmth of spring and early 
summer begins to make itself felt, a crust forms over 
many kinds of dry-farm soils. This is especially true 
where the soil is of the distinctively arid kind and 
poor in organic matter. Such a crust should be 
broken early in order to give the young plants a 
chance to develop freely. This may be accomplished, 
as above stated, by the use of a disk, corrugated 
roller, or ordinary smoothing harrow. 
When the young grain is well under way, it may be 
found to be too thick. If so, the crop may be 
thinned by going over the field with a good iron- 
tooth harrow with the teeth so set as to tear out a 
portion of the plants. This treatment may enable 
the remaining plants to mature with the limited 
amount of moisture in the soil. Paradoxically, if 
the crop seems to be too thin in the spring, harrowing 
may also be of service. In such a case the teeth 
should be slanted backwards and the harrowing done 
simply for the purpose of stirring the soil without 
injury to the plant, to conserve the moisture stored 
in the soil and to accelerate the formation of nitrates. 
The conserved moisture and added fertility will 
strengthen the growth and diminish the water re- 
quirements of the plants, and thus yield a larger crop. 
The iron-tooth harrow is a very useful .implement 
