DEPARTMENT OF AGRICULTURE 23

may be such as to lead to the production of tobacco of an
undesirable quality. Heavy broadcast applications of manure
are not recommended for the same reason. However, light
applications of manure, particularly on the poor spots in the
field, may be used advantageously provided the manure is
free of tobacco diseases.
 It is recommended that not less than one-fifth of nitrogen
be derived from nitrate nitrogen. A one-third ration of nitrate
S nitrogen is not excessive and when used under growing con-
ditions such as shown in figure 9 this leaf roll condition does
not exist.
 Figure 9 shows tobacco leaves damaged by excessive am-
monia nitrogen. This type of growth has been observed on
soil of low pH value and also on soils of good pH for tobacco.
A low nitrate carrying fertilizer, on a medium acid soil or
on one that has been fumigated will also give similar growth.
As the nitrifying organisms build up and with warmer weather
this growth condition will change to normal leaf development.

 High organic nitrogen fertilizers have not been any more
desirable than all mineral or chemical sources of nitrogen under
both irrigated and non-irrigated conditions in Florida. Tests


Fig. 10: The Effect of Phosphorus on the Growth of Tobacco. Left: 40
 pounds per acre; Right: 120 pounds per acre.