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 pur- 
poses only by irrigation and dry-farming. A. per- 
fected 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 agricul- 
tural development of humid regions. Until re- 
cently, 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. 
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