Washington, D. C. July, 1926 
FERTILIZER EXPERIMENTS WITH ALFALFA CONDUCTED AT THE UNITED 
STATES YUMA FIELD STATION, BARD, CALIF., 1919 TO 1925 
By H. L. Westover, Agronomist, Office of Forage Crops, and Epwarp G. NoBLe, 
Farm Superintendent, Office of Western Irrigation Agriculture, Bureau of Plant 
Industry 
CONTENTS 
Page Page 
introductions 2) sa3s es aetna ICs Ee tec taonEsceduyieldsas ea seis. oy ae ee 8 
Historical and statistical data____------------ 1 | Sources of supply of acid phosphate__________ 
bxpermental results. 22.225. 355 pees Sek Bia SAS ULIMIT ATA yer eee or ee eee ue eee 10 
XMeRIeN Ces Of taALIMECL Sse sas ee 7 
INTRODUCTION 
The agriculture of the Yuma Reclamation Project has been built 
up largely around the alfalfa-hay and alfalfa-seed industries. From 
the beginning these crops have constituted and to a large extent still 
represent the real backbone of the farming operations. Naturally, 
when the yields began to decline a few years ago the farmers became 
much concerned. This led to the need of experimental work to 
assist In arriving at some satisfactory explanation for the decreasing 
yields. With this in mind, some rather simple fertilizer experiments 
were begun in 1919 at the United States Yuma Field Station, Bard, 
Calif., the results of which indicated the efficiency of available phos- 
phoric acid. Further tests have shown pretty conclusively that 
phosphoric acid when applied in the form of acid phosphate increases 
the alfalfa yields sufficiently to render its use very profitable. Some 
of the details of these tests are presented in the following pages. 
HISTORICAL AND STATISTICAL DATA 
The agricultural area of the Yuma Reclamation Project comprises 
about 110,000 acres lying on both sides of the Colorado River in 
California and Arizona and situated just north of the Mexican line. 
About 65,000 acres of this land lies in the valley, and before the con- 
struction of levees was subject to overflow. The valley soils are 
alluvial in origin and range in texture from almost pure sand to 
heavy clay. Except where they are highly impregnated with alkali 
or else very sandy, the soils in general have been very productive. 
Farming was begun in the Yuma Valley about 1890. The early 
agriculture was confined to the production of grain and alfalfa. 
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