30 _ BULLETIN 512, U. S. DEPARTMENT OF AGRICULTURE. 
susceptible to overtopping during the next rain. Also the finer, 
lighter, and more fertile particles of soil remain suspended in the 
moving water and are carried off the field. In-such cases, by the 
use of excessive grades, the very cream of the soil is lost. Where 
erosion of a terrace takes place no attempt should be made to culti- 
vate the terrace. It should be seeded to grass. 
COMPARISON OF TERRACE TYPES. 
In order to show the relative merits of the bench terrace and the 
various forms of broad-base ridge terraces, the table below was pre- 
pared. Under the column headed “Least amount of erosion” is 
found the broad-base level-ridge terrace ranking first and the 
uniform-graded terrace last. Since the primary object of terracing 
is to reduce erosion, this advantage should have the greatest weight 
when considering the merits of the different types. The broad-ridge 
terrace is much superior to the bench type of terrace when consider- 
ing the “ Least waste land or weeds.” The embankment of broad- 
ridge terraces can be cultivated successfully and hence no land is lost 
to cultivation or weeds allowed to grow on the terrace. 
Showing how terraces rank with respect to various advantages. 
Fewest Best adapted to— 
Least | Least | ter- | Easeof Seer 
Type of terrace. amount} waste |racesre-| culti- od aid ian 
of ero- |land or| quired | vating| Per- | Imper- F 
sion. | weeds. |in field.| land. | vious | vious Steer builder. 
; soils.1 | soils. | S OPES: 
Horizontal and sloping bench.....-.-- 2 2 3 2 
Broad-base level ridge .-......------- | 1 1 3 1 
Broad-base uniform-graded ridge ---. 4 1 2 1 
Broad-base variable-graded ridge --- ; 3 1 1 1 
1 With reference to least amount of erosion. 
Under the column headed “ Fewest terraces required in field,” the 
graded terrace ranks ahead of the level type owing to the fact that 
by giving the terraces considerable fall they may be spaced farther 
apart than level terraces. However, the greater vertical spacing can 
be used only at a cost of greater erosion to the field. 
Broad-terraced fields are easier to cultivate than the bench type 
since implements and large machinery can be moved across the broad 
terraces and if desirable the rows can be run at any angle. With the 
bench type each bench must be cultivated separately, and difficulty is 
encountered in getting implements from one bench to another. 
From the standpoint of erosion the broad-base level-ridge terrace 
is best adapted for use on pervious soils; on impervious soils the 
graded terrace can be used to the best advantage since in the former 
case most of the water is drained off through the soil and in the 
latter the water is drained off the field over the surface. 
