CRAZY-TOP DISORDER OF COTTON 7 
of Pima cotton; there being few normal plants within the confines of 
the area, an outside zone is noticeable where there is an abrupt change 
from diseased to healthy plants. The field as a whole was very pro- 
ductive, and only a few such spots were present. 
RELATION OF SOIL PERMEABILITY TO CHARACTER AND 
INCIDENCE OF THE DISORDER 
The most aggravated cases of crazy- top have been found associated 
with areas where the soil shows unusual cementing properties or 
where impervious layers occur within two or three feet of the surface 
of the ground. Skinner and Demaree (9) reported that "the un- 
favorable character of the subsoil is evidently an important factor in 
causing [pecan] rosette" and referred particularly to subsoils that are 
stiff and hard. 
In 1923 soil samples wer6 taken from 31 distinct spots in 9 cotton 
fields that were badly affected by crazy-top in the Salt River and 
Casa Grande Valleys. Equal numbers of borings were made in the 
nearest areas where all the plants were normal, usually within 200 feet 
of the affected spots. In seven of the fields the soil within the affected 
spots was definitely harder and obviously more impervious to water 
than the soil in areas where the plants were normal. Iu one field it 
was difficult to find large groups of normal plants, and hard layers were 
encountered both in the definite spots and where the disorder was 
only scattered. By 1925 nearly all of the plants in this field had crazy- 
top symptoms. In the other field, where no material differences were 
noted between the areas of distorted and normal plants, the land had 
bee i cropped to cotton for seven successive years. The soil was mot- 
tled with caliche materials, but a heavy irrigation just previous to the 
examination had penetrated to a depth of 3 or 4 feet. 
At the beginning of the season the occurrence of crazy-top was first 
noted in areas where recently the symptoms had been most severe. 
These areas are characterized by soil of an extremely impervious 
nature. In one of these fields, near Scottsdale, Ariz., the entire area 
of 55 acres was severely affected in 1923, except a narrow strip 
bordering a canal where the soil was deeper than in other parts of 
the field. It was found impracticable to obtain soil samples to a 
depth greater than 3 feet in the worst affected part of this field in 
September, 1923, on account of the hard formation of caliche and 
decayed granite composing the subsoil. An average of 40 strokes 
with a 16-pound hammer was required to penetrate the third foot in 
the crazy-top areas, whereas the area along the canal was sampled 
five feet deep with ease. Deranged plants were observed in this 
field in late July in 1923 although the disorder was not evident 
in neighboring fields until late August. This field was ratooned 
in 1924, and the symptoms were observed on the young cotton 
shoots as early as May 27. 
In another field near Casa Grande the impervious nature of the soil 
made it impracticable to obtain adequate penetration of water after 
July 1. The disorder was identified on the shoots of the ratooned 
plants on April 1, 1924, and on seedlings in the same area as early as 
June 1 1 . The groups of plants growing in these obviously unfavor- 
able locations show extreme morphological distortions of growth in 
the autumn and seldom set any bolls. Where there was evidence of 
somewhat deeper penetration of water the symptoms were more mild 
and a greater number of bolls were matured. 
