38 BULLETIN 1381, U. S. DEPARTMENT OF AGRICULTURE 
The results of the experiments on seed-bed preparation for rice 
grown by continuous suomergence show that the best yields were 
obtained on well-prepared seed beds on which the rice was sown 
broadcast and immediately submerged 4 to 6 inches. On unpre- 
pared or poorly prepared seed beds such weeds as spike rush, cat- 
tail, and slender aster reduce rice yields below profitable limits. 
The results show that on land foul with cat-tail, a heavy rate of 
seeding (200 pounds per acre) does not help to eradicate it. Good 
stands of rice do aid, however, in preventing cat-tail from becoming 
established on a clean rice field. 
The results of continuous cropping to rice indicate that profitable 
yields can not be obtained for more than six years in succession by 
the old methods of irrigation, even when weeds are kept under con- 
trol, and that continuous cropping probably will not be practicable 
when irrigating by continuous submergence. 
The varietal experiments show that medium-grain and long-grain 
rices are not so well adapted to California conditions as the short- 
grain rices. During the six-year period from 1919 to 1924, inclusive,* 
Selection No. 1561-3, a mid-season short-grain rice with an average 
acre yield of 2,971 pounds, was the highest-yielding variety. Selec- 
tion No. 115, a late short-grain rice, produced an average acre yield 
for the same period of 2,820 pounds. For the same period Selection 
No. 113, a mid-season long-grain variety, and Early Prolific, a mid- 
season medium-grain variety, produced average acre yields of 2,410 
and 2,129 pounds, respectively. 
Colusa (C. I. No. 1600), an early-maturing short-grain variety, 
matures in 143 days from the date of the first irrigation; Caloro, a 
mid-season variety, in 156 days; and Wataribune (C. 1. No. 1561), a 
late short-grain variety, in 167 days when irrigated by the old method. 
Of 17 varieties and selections of early, mid-season, and late short- 
grain rices grown on small increase plats from 1920 to 1924, inclu- 
sive, the highest average yields were produced by mid-season selec- 
tions, the late group ranking second in yield. 
The average increase in yield of 14 varieties grown on bur-clover 
land when compared with the same varieties grown on mung-bean 
and soy-bean land was 1,778 pounds per acre, or 38 per cent. 
The yield of 63 varieties grown in head rows and also 115 varie- 
ties grown in bulk rows in the rice nursery from 1918 to 1923, inclu- 
sive, are presented. Bulk rows produced higher average yields per 
row than head rows, apparently because of heavier seeding. In 
general, mid-season and late short-grain varieties and selections gave 
higher average yields in the nursery than the medium or long grain 
types. 
