RICE CULTURE IN CALIFORNIA 13 
harrowed. For the 1923 and 1924 crops the land was spring plowed, 
double disked, harrowed, and dragged. Each year these tillage opera- 
tions provided a good seed bed. 
The annual yields of all except the check plats represent the 
average yields of two tenth-acre plats. The annual yields of the 
broadcast checks are for two plats irrigated by the old method. The 
annual yields of the drilled checks are the average of four plats in 
all cases except the yield recorded for the May 5 seeding in 1923, 
which is for only two plats. 
In these experiments alternate plats, usually inclosed by the same 
levees, were sown broadcast and drilled, respectively. Each year 
the rice was irrigated and the plats drained three times before the 
plats finally were submerged to the required depths. On the date 
of submergence the rice and water grass varied in height from 
1 to 2 inches. 
The plats submerged 2 and 4 inches were very foul with water 
grass and sprangletop each year, but were worse in 1923 and 1924 than 
in 1922. On plats submerged 6 and 8 inches the water grass was con- 
trolled to a marked extent, but at these depths a good deal of rice 
also was suffocated each season. Some barnyard grass and sprangle- 
top were present on all plats each year, but these grasses were much 
more abundant on the control plats and those submerged 2 and 4 
inches than on plats submerged 6 and 8 inches. 
Table 8 shows the annual and average acre yields from plats sown 
both broadcast and drilled on two different dates and submerged at 
various depths after the rice emerged in 1922, 1923, and 1924, inclu- 
sive. Each year better stands and higher yields were obtained from 
plats sown on April 25 than from those sown on May 5. In 1922 and 
1923 the yields from the plats sown on April 25 were so much higher 
than from those sown on May 5 that the latter date of seeding was 
omitted in 1924. 
The average acre yields for both dates of seeding show that at 
each depth of submergence the average yields of the drilled plats were 
higher than those of the broadcast plats except for the plats sown 
on May 5 and submerged 8 inches. The increased yields from the 
drilled plats, however, in most cases are small and therefore probably 
not significant. 
The three-year average acre yield of the plats sown on April 25 and 
submerged at various depths after the rice emerged shows an increase 
above the check plats ranging from 73 to 283 pounds. The highest 
average acre yield, 2,163 pounds, was obtained from drilled plats sub- 
merged 2 inches after the rice emerged. But the difference in yield of 
plats submerged 2, 4, 6, and 8 inches is not sufficient to indicate witli 
any certainty that in this case one depth of submergence is distinctly 
superior to another. This method of irrigation, based on the result'.- 
presented in Tables for the April 25 date of seeding, is not markedly, 
if at all, superior to the old method of irrigation. The submergence < ■!' 
drilled or broadcast rice soon after emergence is decidedly inferior to 
continuous submergence immediately after the rice is sown broadcast 
(Table 6), both in regard to water-grass control and to rice yields. 
