Departmental Activities. 25 



Mr. Blatt, after an extensive inquiry, lias furnished the follow- 

 ing interesting report: — 



Bearing Life of Citrus Trees. — The profitable bearing life of 

 citrus in California is limited to 30 or 35 years — this is the common 

 statement — whereas many trees have been known to reach 100 years. 

 Decline of orchards are due to a combination of causes. Failure to 

 care for trees properly; lack of attention to irrigation, fertilization, 

 pruning, pest, and disease control, particularly tree butchery instead 

 of pruning, and excessive irrigation have been responsible for the 

 decline and loss of large acreage of orchards. On the other hand, 

 there are orchards which have received the best care, and their 

 decline cannot be attributed to any of the above causes, but is due 

 to some specific cause or causes. 



Professor Hodgson, Farm Advisor of Los Angeles County, has 

 studied this problem particularly, hence he is considered an authority 

 on the subject. He is convinced that the two principal factors 

 contributing to the early decline of citrus orchards are: — 



1. Inability to feed tlie soil normally, occasioned through 



improper methods of applying fertilizers. 



2. Slow but certaiii poisoning of the trees through absorp- 



tion of toxic compounds given o& by a variety of trunk 

 and root disease producing fungi. 



The citrus tree is essentially a mat-rooted tree ; the feeder roots 

 are in the main produced from long laterals, which parallel the 

 ground surface at depths ranging from 4 to 24 inches. 



In its native habitat the citrus tree is a surface-feeding plant, 

 the fibrous feeder roots coming very close to the surface, forming 

 rather extensive mats and feeding uninterrupted and undisturbed 

 just underneath the damp mulch of leaf mold. The citrus tree 

 naturally attempts the same thing all over, but in semi-arid climates 

 the surface foot of soil becomes too hot, hard, and dry for the health 

 of the feeder roots. Fertilizers are applied on the surface as a rule, 

 and are ploughed in or cultivated in little deei)er than the soil 

 mulch. The feeder roots are also constantly receiving rebuffs, such 

 as shearing oft' by ploughing and cultivating, and periodic baking 

 and cooling; the result is starvation in plenty, the needs of the tree 

 during the early years being met from the deeper soil stretches, and 

 when these become depleted, which is the case soon after, since 

 fertilizers are not applied deep enough, the tree begins to go back 

 and weaker feeder roots are developed. Surface mulching with 

 organic matter, therefore, has given surprising results in bringing" 

 back deteriorating trees : unfortunately the recovery is only tem- 

 porary — three years at the most — when signs of decline are again 

 noticed, hence surface mulching does not constitute a cure for orchard 

 decline. It does, however, furnish a valuable means of quick recovery 

 for ailing trees. 



The furrow-manuring method of applying not only manures, 

 but other organic fertilizers and all other save the most soluble forms 

 of fertilizers, will do more to prevent the decline of citrus orchards 

 than anything that might be done. One large furrow, 12 to 15 

 inches in depth, located between rows, is all that is necessary: the 

 manure or fertilizer is placed in the furrow and covered up. A 



