16 BULLETIN 1155, U. S. DEPARTMENT OF AGRICULTURE. 
The soil on which this experiment was conducted is Stockton clay 
adobe. The land was fall-plowed each year except 1918, well pre- 
pared in the spring before seeding, and kept free from water grasses 
and tules. Plowing for the 1918 crop was not done till the spring of 
that year. New land usually produces about one-third more per 
acre than second or third year land. The yields just stated do not 
show a gradual decline as the land becomes old, but erratic changes, 
possibly due to favorable or unfavorable weather conditions in 
different years. The yield in 1914 was less than in 1915 and about 
the same as in 1917. In 1918 and 1919 the yields were much lower 
than in the preceding years. The average yield for the 7-year period 
was 3,528 pounds per acre, which is above the average yield for the 
State each year. 
These yields show that if weeds are kept under control the land will 
produce rice for at least seven years in succession, though com- 
mercially it has not been possible to grow rice more than three or 
four years in succession, because the cost of eradicating weeds was 
prohibitive. 
Land that is foul with water grasses and cat-tails, if spring-plowed 
and fallowed, will grow barley or wheat the following year, after 
which a crop of rice can be grown. 
IRRIGATION EXPERIMENTS. 5 
The irrigation experiments at the Biggs Rice Field Station have 
been conducted cooperatively by the Office of Cereal Investigations 
of the Bureau of Plant Industry and the Office of Irrigation Investi- 
gations of the Bureau of Public Roads and Rural Engineering. 
When these experiments were started in the spring of 1914, the rice 
industry in California was still in its infancy. Information regarding 
the best methods of irrigation for rice was sorely needed. 
The plan of the experiments included a study of the effect of 
varying the dates of submerging the rice crop, of varying the depth 
of submerging the crop, of fluctuating the depth of water during the 
submergence period, of slow changing versus stagnant water during 
submergence, and of no submergence but the ground kept wet by 
frequent irrigations. During the conduct of these experiments water 
grass had not become so much of a menace as it now is, and the experi- 
ments were therefore concerned primarily with yield under the 
different irrigation treatments rather than with water-grass control, 
which has since become one of the chief subjects of investigation. 
The irrigation experiments were conducted on fifth-acre plats in 
1914. 1915, 1916, 1918, and 1920. In 1917, 1919, and 1921 the 
experiments were on tenth-acre plats. In 1914 the irrigation experi- 
ments were on new land, in 1915 on second-year land, in 1916 on 
third-year land, in 1917 and 1918 on fallowed land that had produced 
three rice crops, in 1919 and 1920 on fallowed land that had produced 
four rice crops, and in 1921 on fallowed land that had produced five 
rice crops. Good stands were obtained each year. 
6 For further data on the irrigation of rice in California, see Adams, Frank, Rice irrigation measurements 
and experiments in the Sacramento Valley, 1914-1919, Calif. Agr. Exp. Sta. Bui. 325, p. 45-69, 4 fig., 1920. 
