RICE CULTURE IN CALIFORNIA 19 
WEED CONTROL 
Effect of good preparation. — On well-prepared seed beds there was 
very little water grass on plats continuously submerged 4, 6, and 8 
inches, except for the white, or " Japanese, " barnyard grass, which 
was present to a considerable extent on all plats in 1921 and 1922 
and was sufficiently thick in 1923 to reduce rice yields materially. 
The results indicate that white water grass can not be controlled 
by continuous submergence at these depths. Observations along 
" barrow pits " at the base of levees and in dead furrows indicate that 
water ranging from 10 to 15 inches deep does aid materially in the 
control of white water grass. At such depths, however, it is dif- 
ficult to get good stands of rice, and it is impracticable also to hold 
the water so deep. It therefore appears that white water grass when 
thin should be hand pulled to prevent spreading. 
Effect of no preparation. — The plats sown in 1922 on stubble land 
without seed-bed preparation and those sown in 1924 on double-disked 
stubble land were very foul with spike rush, cat-tail, slender aster, and 
canary grass. Barnyard grass also was much thicker than on plats 
which were spring plowed. Some water grass usually germinates in 
the spring before the rice land is prepared for seeding, and such plants 
must be killed by cultivation, as it is practically impossible to control 
or suffocate them with water 6 to 8 inches deep. 
Control of cat-tail. — Seeding at the rate of 200 pounds per acre on 
land badly fouled with cat-tail did not check its growth. However, 
observations during past years indicate that on clean land good stands 
of rice are very helpful in preventing cat-tail from becoming estab- 
lished. Cat-tail usually first appears in a field where the stands of 
rice are poor; that is, along the levees and on low land where it is 
difficult to obtain good stands of rice. 
YIELD DATA 
Table 11 presents the annual and average acre yields from the 
seed-bed preparation experiments for the three-year period. On a 
well-prepared seed bed there is little difference in the average acre 
yields of plats sown broadcast and immediately submerged 4, 6, or 
8 inches. The average yield of the plats sown broadcast in 6 inches 
of water was considerably less than for the plat sown broadcast and 
immediately submerged 6 inches. The yields on unprepared and 
poorly prepared seed beds, while fragmentary, indicate that there is 
more effect on yield from depth of submergence. All of the data 
taken together show conclusively that good seed-bed preparation is 
a desirable practice. On poorly prepared seed beds acre yields are 
materially reduced by competition with weeds, such as spike rush, 
cat-tail, slender aster, and water grass. 
RATE-OF-SEEDING EXPERIMENTS 
EFFECT OF VARIETY 
Those who are familiar with the growing of cereal crops know that 
the maximum yield of a given variety is not likely to be obtained from 
the same rate of seeding every year. However, in a period of years 
