Farm Types in Nebraska 
11 
Fig. 4. — Soil the limiting factor within favorable agricultural regions. 
the difficulty of ; obtaining food. It may be added in con- 
nection with these statements that our inability to control 
bodily temperature is one of the chief hindrances to a suc- 
cessful intensive tropical agriculture. 
From the foregoing discussion it can easily be seen that 
Nebraska data will bear heavily upon moisture problems 
I such as are common to areas near the center of the Great 
Plains. Altitude in the extreme western part of the State 
adds to what would otherwise be a short scale in heat differ- 
ences. As concerns soil, there is almost a complete scale in 
both texture and topography. 
THE EFFECT OF HEAT UPON THE ACREAGE OF CROPS 
TREATED AS ANNUALS* 
A CLASSIFICATION OF FIELD CROPS 
! Most field crops can be classified as either annuals, bien- 
5 nials, or perennials. In field practice biennial crops have no 
*For a number of the ideas presented in this division of the bulletin the author 
is indebted to Professor E. Hopt, formerly in cbarsre of Field Crops instruction 
in the College of Agriculture, University of Nebraska. 
el- 
