EOSETTE OF PECAN TREES 11 
NITROGEN 
The nitrogen content of soil from healthy sections of each orchard 
is greater than that from the rosetted sections in 7 cases of the 11 
examined. Even where the reverse is the case, the nitrogen content 
of both soils is very nearly the same. The ratio of nitrogen to 
organic matter is not exactly the same in any two samples of soil. 
ACIDITY 
All of the soils examined,, except one, were found to be acid in re- 
action. The acidity is given in terms of P n values which were 
determined by the hydrogen-electrode method. There is no apparent 
relation between the degree of acidity of the soil and the quantity 
of pecan rosette in the orchard- examined. In seven of these orchards 
the soil from the rosetted sections was found to be slightly : 
acid than that from the healthy sections, in one orchard the degree 
of acidity was the same in both soils, and in three the acidity was 
less. There was no wide variation in the degree of acidity in any of 
these soils except in orchards Xos. 2, 6, and 11, and from the data 
procured it would seem that a slight degree of acidity is not a fa 
in causing rosette. 
In orchard Xo. 2 the soil from the rosetted section was 1 
than that from the unrosetted section. The acidity (P H ) value was 
5.7 and 4.2, respectively. In orchard No. 6 the soil from the rosetted 
section was alkaline, having a P H value of 7.7. and that from the 
healthy section was slightly acid, having an acidity (P H ) value of C.l. 
On the other hand, in orchard Xo. 11 the soil from the rosetted sec- 
tion was more acid than that from the healthy section, the acidity 
(P H ) value being 5.4 and 6.1, respectively. There is nothing in these 
data to show that there is any relation between slight degree 
acidity and rosette. 
ORCHARD CULTURE 
/ 
The growing of leguminous cover crops for green manuring or the 
application of stable manure has been responsible for the greater 
organic-matter content of the soil in the healthy sections of most of 
the orchards examined. 
CONDITION OF THE SUBSOIL 
The unfavorable character of the subsoil is evidently an important 
factor in causing rosette of pecan trees, but only a few cases in the 11 
orchards examined permit study of this factor. In orchard Xo. 3 
the subsoil from the diseased section was very stiff and hard, which 
was not the case in the healthy sections and was probably the prin- 
cipal factor in the cause of the rosette. It was also a possible factor 
in orchard No. 7, where the subsoil was stiffer and harder in the dis- 
eased than in the healthy section. The rosetted condition of a sec- 
tion of orchard No. 5 may be due to the deeper and more porous 
nature of the subsoil. In the other orchards mentioned in Table 10 
the subsoil conditions were similar in the rosetted and healthy sec- 
tions. 
