PREFACE





Nearly six tenths of the earth's land surface receive an annual
rainfall of less than twenty inches, and can be reclaimed for
agricultural purposes only by irrigation and dry-farming. A
perfected world-system of irrigation will convert about one tenth of
this vast area into an incomparably fruitful garden, leaving about
one half of the earth's land surface to be reclaimed, if at all, by
the methods of dry-farming. The noble system of modern agriculture
has been constructed almost wholly in countries of abundant
rainfall, and its applications are those demanded for the
agricultural development of humid regions. Until recently irrigation
was given scant attention, and dry-farming, with its world problem
of conquering one half of the earth, was not considered. These facts
furnish the apology for the writing of this book.

One volume, only, in this world of many books, and that less than a
year old, is devoted to the exposition of the accepted dry-farm
practices of to-day.

The book now offered is the first attempt to assemble and organize
the known facts of science in their relation to the production of