66 



ANNUAL REPORT 1918 AND 1919 



A lengthy consideration of the chmatic conditions in different parts 

 of Mexico is not within the scope of this report. It will suffice to mention 

 a few important characteristics of some of the principal avocado regions. 



The West Indian race seems to find optimum conditions of growth 

 and fruit production in regions where high temperatures are combined with 

 reasonably heavy precipitation. The regions of very heavy rainfall do 

 not seem to produce as good fruits as those where there is a dry season of 

 considerable length and where the amount of precipitation during the year 

 is not over 75 or 80 inches. 



The Mexican race, on the other hand, does not seem to be as suc- 

 cessful on the coast as at considerable elevations. This is probably due 

 to the fact that its native home is in the mountains at elevations of 4000 

 to 6000 feet. It has seemed to me that it finds optimum conditions for 

 growth and fruit production at elevations of 5000 to 6000 feet, and in 

 regions where the climate is comparatively dry. I believe this race is 

 naturally adapted to withstand a dryer atmosphere than the West Indian. 



Taking the climate of Queretaro, for example, as representative of 

 the optimum for this race, we find it to resemble rather strikingly that of 

 southern California. The rainfall is perhaps slightly greater (I have not 

 yet been able to obtain meteorolgical data), and occurs at a different 

 season of the year, but the temperatures seem to be very much the same, 

 and the relative humidity is low, though perhaps not so low as in California. 

 With such a climate, good soil, and the proper irrigation, the conditions 

 seem to be almost ideal for this race. 



The soil in the avocado groves of Queretaro is a clay loam, in places 

 heavy enough to be termed clay. I am coming more and more to believe, 

 as I examine the soils of the different avocado regions of tropical America, 

 that the avocado greatly prefers a heavy soil to a light one. In these 

 countries it is very common to find trees growing and fruiting well on 

 heavy clay; the best results which I have seen were obtained on clay 

 loam. Very light soils are rare; I have seen nothing in Mexico so porous 

 as the volcanic soil of Antigua, Guatemala. But volcanic soils, even 

 though light and friable, are usually rich in plant food, I believe. From 

 what I have seen, I would conclude that the avocado prefers a good strong 

 soil; a soil well drained, but rather heavy, and not sandy or exceedingly 

 friable. We know from experience, of course, that the avocado will 

 succeed on a wide range of soils, but it is still something of a question 

 which type may be considered ideal. If I were going to plant an orchard, 

 I would look for a small valley where an alluvial soil had been formed of 

 material washed down from mountains or hillsides where clay predomi- 

 nated. I am speaking now of Mexico; it might be dangerous to plant in 

 a valley in California because of the exposure to frosts. 



So far as I have been able to observe up to the present all races of 

 the avocado have this same preference for a heavy soil. I have not been 

 able as yet to distinguish any differences in this respect. At Orizaba the 

 West Indian, the Mexican, and the Chinini are all three grown in great 

 abundance, often side by side. The land is sloping, hence well drained, 

 and the soil varies from a heavy loam to clay. It seems to give excellent 

 results. 



I believe it will be well for Californians to keep in mind this prefer- 

 ence when selecting land for an avocado orchard. 



