RICE CULTURE IN CALIFORNIA 7 
June, July, and August are the months of highest evaporation. 
The average evaporation for these three months for the 12-year period 
from 1913 to 1924, inclusive, was 24.834 inches. The average evap- 
oration from June to October, inclusive, for the 11-year period from 
1913 to 1923, with 1917 omitted, was 34.02 inches, with a range 
from 27.136 inches in 1922 to 44.571 inches in 1913. 
EXPERIMENTS ON THE CONTROL OF WATER GRASS AND ITS 
VARIETIES 
METHODS USED 
The term "water grass" as used in this bulletin includes all forms 
of water grass (EcMnocJiloa crusgalli) and its varieties except the 
white, or " Japanese," barnyard grass. 
Experiments to control water grass by continuous submergence 
were started at the Biggs Rice Field Station in 1921. The results 
obtained in that year have been published. 2 
Experiments are being conducted at the station to determine, if 
possible, the best method of seed-bed preparation, date and rate of 
seeding, and date and depth of submergence for rice when grown by 
continuous submergence after broadcast seeding or when submerged 
soon after the rice emerges. These experiments were planned also 
to study the effect of the different irrigation methods on the control 
of water grass and on the yields of rice. 
The work on water-grass control herein reported covers (1) exper- 
iments on immediate submergence after seeding, including the effect 
of sowing broadcast on the soil and in the water and the effect of 
drilling the seed; (2) experiments on depth of submergence after the 
rice has emerged, including a comparison of broadcasting and drill- 
ing seed and comparison of spring plowed and disked stubble land; 
(3) experiments on rate of seeding and method of irrigation; and 
(4) experiments on seed-bed preparation, including comparison of 
the effects of good preparation and poor or no preparation and the 
control of cat-tail by heavy seeding. In most of these experiments 
the dates of seeding and depth of submergence also were varied. 
None of the rice sown broadcast was harrowed or covered after 
sowing. On plats submerged at specified depths the water was 
maintained at as near the depths stated as was possible under field 
conditions until the land was drained for harvest. All plats were 
sown at the rate of 150 pounds per acre unless otherwise stated. 
The few" Japanese," or white, barnyard-grass plants which appeared 
were hand pulled in all experiments, except those on seed-bed 
preparation. 
During the crop years 1922 and 1924, the temperature was favor- 
able for rice production, but during the crop year 1923 the tempera- 
ture was apparently too cool for maximum yields of rice. 
EXPERIMENTS ON IMMEDIATE SUBMERGENCE AFTER SEEDING 
Experiments involving immediate submergence after seeding were 
conducted in 1922, 1923, and 1924 on land that had been continu- 
ously cropped to rice in the fertilizer experiments from 1913 to 1920, 
2 Jones, J. W. Op. cit 
