8 
Bulletin 69 . 
trees appeared to be perfect^ healthy and had made a vigorous 
growth which showed no sign of disease. This experiment tends to 
confirm the conclusion that the difficulty is due to local conditions 
and not to a specific organism which might spread to other portions 
of the vallev. 
Apparent^ the same difficulty is figured and described in a 
recent California bulletin in which the author ascribes the cause to 
the presence of alkalies in the soil. He states that apple trees are 
injured “ by 1,200 pounds of carbonate and 3,000 pounds of common 
salt per acre distributed through four feet depth.” 
The particular soil on Rogers Mesa that was examined con¬ 
tained 1,820 pounds of common salt per acre taken to a depth of 
one foot. While this is a much larger amount of salt than the trees 
are said to be able to endure in California, most of the trees do not 
show any sign of the affection, though they have been planted nine 
years. This statement is confined to the first foot of soil, because it 
is doubtful if there is any portion of the orchard where the soil is 
four feet deep. Moreover, the subsoil is a marl into which the 
trees had thrown very few roots. 
The amount of sodic carbonate in this soil was not determined. 
However, we have had occasion to observe a nursery that was estab¬ 
lished in a soil in which the sodic carbonate content was determined 
and found to be 2,800 pounds per acre, taken to a depth of four feet. 
The trees made an excellent growth for three years and showed no 
sign of the rosette affection. 
While these observations do not prove that this condition of 
apple trees may not be produced by the action of alkalies, they 
point to the conclusion that such an effect is improbable under our 
conditions. 
Treatment .—Apple trees should not be planted on soil where 
the marl substratum comes close to the surface, as it will result in 
shallow-rooted trees with its attendant evils. In other portions of 
the district an attempt should be made to make the soil deeper and 
to add to it substance and fiber. Many Colorado soils are deficient 
in vegetable matter, consequently they become compact and dry out 
rapidly. Depth may be gained by plowing deeply before the orch¬ 
ard is planted, and vegetable matter added by turning under strawy 
stable manure or green manure. For the latter purpose some form 
of clover, vetch or rye may be used, preferably in the form of a cover 
crop, which should be sown in the latter part of summer and plowed 
under during the following spring. If water for fall irrigating is 
available the crop will make growth sufficient to afford considerable 
protection to the roots against the action of frost and from drying 
out by winter winds. Finally, by a judicious use of water, of which 
*Laughridge, R. H. “Tolerance of Alkali by Various Cultures.” Calif. Agri. 
Expt. Sta. Bull. 133:14. 
