16 BULLETIN 1378, U. S. DEPT. OF AGRICULTUBE 
matter and nitrogen in the soils under trees growing in the yards 
near dwellings were much greater than in the adjoining orchards, 
and the nut yields were correspondingly greater. All of these soils, 
as shown by hydrogen-ion exponents, were slightly acid, but prac- 
tically no difference was found between the degree of acidity of the 
soils producing large and small crops of pecans. 
SUMMARY 
Two badly rosetted orchards grown on soils low in both organic 
matter and fertility were subjected to different cultural treatments, 
one of which included plowing, thorough cultivation, and the grow- 
ing and turning under of two green-manure crops each year; the 
second included only a light disking annually and the growing of 
grasses and weeds with no plowing. In the latter case, the vegetation 
produced was cut and removed as hay and none turned under. 
Chemical fertilizers, as used in the experiments, had no influence in 
decreasing or increasing rosette. 
The former treatment was coincident with an increase in the supply 
of organic matter and nitrogen in the soil, which resulted in a gradual 
improvement and finally in the apparently complete disappearance 
of all rosette symptoms on the trees and a return to a normal pro- 
duction of nuts. On the other hand, the second cultural treatment 
was coincident with a decrease of organic matter and of nitrogen in 
the soil and a marked increase of rosette symptoms, resulting in the 
abandonment of the orchard. 
Soils from healthy and rosetted sections of pecan orchards of uni- 
form soil type and of uniform tree age and variety wore examined 
in the held and laboratory. There is a close correlation in these 
orchard soils having a high nitrogen and organic-matter content with 
healthy productive trees and of soils having a low nitrogen and 
organic-matter content with unfruitful rosetted trees. There was no 
correlation of soil acidity with good or poor pecan orchards. 
In orchards free from rosette there is a correlation of high nitrogen 
and organic-matter content of soil with productive trees and of a 
low nitrogen and organic-matter content with poor tree growth and 
poor nut yield. 
It is apparent that the accumulation of organic matter in the soils, 
whether acquired by the growing and plowing under of cover crops 
or by the addition of manures, composts, or debris, is beneficial to 
pecan trees and stimulates increased growth and yield. 
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