36 MANUAL OF TROPICAL AND SUBTROPICAL FRUITS 



most growers, the difference being in the method of carrying the trees 

 through the spring period. The quantity of fertilizer used at each 

 application varies of course with the size of the tree, quantity of fruit 

 it is carrying and the analysis of the fertilizer. For ten year old trees 

 as high as 25 pounds at a single application has been used with good 

 results. For four year old trees, bearing their first crop, four applica- 

 tions of from three to four pounds each, one of four and one-half and 

 one of five pounds have brought the trees through the year in fine 

 shape. As materials from which fertilizers suitable for avocados may 

 be compounded, cottonseed meal, castor pomace, tankage, ground 

 tobacco stems and ground bone are to be recommended, with a cer- 

 tain amount of nitrate of soda used as a source of nitrogen when quick 

 results are sought as in the case of trees which have 'started back.' 

 Previous to the war scarcity of potash, it was thought advisable to 

 use formulae giving from four to six per cent of that element, but the 

 enforced limitations to the percentage of potash obtainable during 

 the past two years has had no apparent ill effects upon the trees or 

 fruit and seemingly a range of from zero to four per cent will provide 

 all the potash that an avocado tree requires under Florida conditions. 

 A formula that has given good results is built up of cottonseed meal, 

 castor pomace, tankage, and ground tobacco stems, analyzing 4 per cent 

 to 5 per cent ammonia, 6 per cent to 7 per cent phosphoric acid and 

 2 per cent potash. 



" The trees were usually cultivated by hoeing three times each year 

 and a heavy mulching of dead grass or weeds during the dry winter 

 season. If instead of the dead grass a mulching of compost or well 

 rotted stable manure is used the results are even more satisfactory and 

 the February application of fertilizer may then be omitted entirely." 



In California, stable manure has been practically the only 

 fertilizer used up to the present. The necessary nitrogen 

 can be obtained from this source, and the organic matter 

 added to the soil is also of benefit. 



Irrigation. 



An abundance of water is especially important during the 

 first two or three years after the tree is planted, if rapid healthy 

 growth is to be maintained. In Florida, particularly in sections 

 where the soil is deep, many young groves have in the past 

 suffered for lack of water. One of the most experienced growers 

 near Miami states that trees which have had abundant irriga- 



