244 SOILS. 



practiced in California, but has now been mostly abandoned 

 for furrow irrigation. The latter has been adopted partly 

 because it requires a great deal less hand-labor, partly under 

 the impression that the whole of the soil of the orchard is thus 

 most thoroughly utilized; partly also because of the injurious 

 effect upon trees produced at times by basin irrigation. 



The explanation of such injurious effects is, essentially, 

 that cold irrigation water depresses too much the temperature 

 of the earth immediately around the roots, and thus hinders 

 active vegetation to an injurious extent, sometimes so as to 

 bring about the dropping of the fruit. This of course is a 

 very serious objection, to obviate which it might be necessary 

 to reservoir the water so as to allow it to warm before being 

 applied to the trees. 1 In furrow-irrigation the amount of 

 soil soaked with the water is so great that the latter is soon 

 effectually warmed up, besides not coming in contact too in- 

 timately with the main roots of the tree ; along which the water 

 soaks very readily when applied to the trunk, thus affecting 

 their temperature much more directly. It is for the farmer to 

 determine which consideration should prevail in a given case. 

 If the water-supply be scant and warm, the most effectual use 

 that can be made of it is to apply it immediately around the 

 tree, in a circular trench dug for the purpose. When on the 

 contrary, irrigation water is abundant and its temperature low, 

 it may be preferable to practice furrow irrigation, or possibly 

 even flooding. 



As to the supposed more complete use of the soil under the 

 latter two methods, it must be remembered that while this is 

 the case in a horizontal direction, if irrigation is practiced too 

 copiously under the shallow-furrow system, it may easily hap- 

 pen that the gain made horizontally is more than offset by a 

 corresponding loss in the vertical penetration of the root- 

 system. This is amply apparent in some of the irrigated 

 orange groves of southern California, where the fine roots of 

 the trees fill the surface soil as do the roots of maize in a 

 corn field of the Mississippi States; so that the plow can hardly 

 be run without turning them up and under. In these same 

 orchards it will often be observed, in digging down, that at a 

 depth of a few feet the soil is too water-soaked to permit of 



1 See below, chap. 17. 



