110 MANUAL OF GARDENING 
in Fig. 116. A marker can be rigged to a wheel-barrow, as in 
Fig. 117. A rod is secured underneath the front truss, and 
from its end an adjust- 
able trailer, B, is hung. 
The wheel of the bar- 
row marks the row, and 
the trailer indicates the 
place of the next row, 
thereby keeping the 
rows parallel. A hand 
sled-marker is shown 
in Fig. 118, and a simi- 
lar device may be se- 
cured to the frame of a sulky cultivator (Fig. 119) or other 
wheel tool. A good adjustable sled-marker is outlined in Fig. 
120. 
119. Trailing sled-marker. 
Enriching the land. 
Two problems are involved in the fertilizing of the land: 
the direct addition of plant-food, and the improvement of the 
physical structure of 
the soil. The latter 
office is often the more 
important. 
Lands that, on the 
one hand, are very 
hard and solid, with a 
tendency to bake, and, 
on the other, that are 
loose and leachy, are 
very greatly benefited 
by the addition of organic matter. When this organic matter — 
as animal and plant remains— decays and becomes thoroughly 
incorporated with the soil, it forms what is called humus. The 
120. Adjustable sled-marker. 
