RICE CULTURE IN CALIFORNIA 
15 
irrigated and drained three times before the plats were submerged 
to the required depths. On the date of submergence the rice and 
water grass varied in height from 1 to 2 inches. 
Although the plats submerged 6 and 8 inches grew much less wa- 
ter grass than plats submerged 2 und 4 inches, the stands of rice on 
the more deeply submerged plats were too thin to produce good 
yields. The stands on the deep-water plats also were reduced in 
1922 by injury from leaf miners and by the growth of spike rush. 
Spike rush (Eleocharis palustris), locally known as wiregrass, cat- 
tail ( Typha latifolia) , slender aster (Aster exilis) , annual sedge ( Cy pe- 
rns diff'ormis) , and canary grass (Phalaris) were very thick each year 
on the disked stubble land. The spike rush, slender aster, and cat- 
tail were especially bad on the disked stubble land in 1923 and 1924. 
These weeds are controlled to a large extent by good spring plowing 
followed by drying weather. 
The annual and average acre yields for the method-of-seeding 
experiments on spring-plowed and on disked stubble land submerged 
at various depths after the rice emerged during the years 1922, 1923, 
and 1924 are given in Table 9. 
Each of the four check plats was a single tenth-acre plat each year 
a,nd irrigated in the old way. The yields of plats submerged 2 inches 
are for single fifteenth-acre plats each year. The circled figures in 
Table 9 represent the number of tenth-acre plats averaged where 
more than one was grown. 
Table 9. — Yields of rice obtained on spring-plowed and on disked stubble land, both 
drilled and sownbroadcast and submerged at various depths after the rice emerged, 
at the Biggs Rice Field Station in 1922, 1928, and 192% 
{The circled figures 
represent the number of tenth-acre 
plats averaged where more 
than one was grown] 
Method of 
Submergence 
Acre yields (pounds) 
Seed-bed prepa- 
Com 
pared 
ration 
seeding 
Date 
Depth 
1922 
1923 
1924 
Aver- 
age 
with check 
Gain 
Loss 
Spring plowed 
Drilled 
May 30 
2 
3,510 
2, 115 
2,310 
2,645 
325 
Double disked 
do 
...do.... 
o 
2,430 
1,395 
720 
1,515 
380 
Spring plowed 
Broadcast .. 
...do.... 
4 © 
4 © 
2,585 
GO 
2,235 
1,670 
2,163 
343 
Double disked 
do 
...do.... 
2,180 © 
1,335 
890 
1, 468 
133 
Spring plowed 
Drilled 
...do.... 
4 © 
2,460 
:v 
2,605 
1,820 
2,295 
25 
Double disked 
do 
...do.... 
4 © 
6 ® 
2,455 
i 
1,510 
1,320 
1,762 
133 
Spring plowed 
Broadcast .. 
...do.... 
2,317 
2,037 © 
1,177 © 
1,870 
2,075 
255 
Double disked 
do 
...do.... 
6 © 
1,803 
(£) 
770 
1,250 
85 
Spring plowed 
Drilled 
...do.... 
® 
2,248 
§ 
2,042 © 
2,140 
2,143 
Double disked 
do 
...do.... 
6 © 
2,048 
1,383 © 
975 
1,469 
426 
Spring plowed 
Broadcast .. 
..-do.... 
8 © 
1,360 
w 
1,640 © 
1,610 
1,537 
283 
Double disked 
do 
..-do.... 
8 © 
1,037 
CD 
980 © 
840 
952 
383 
Spring plowed 
Drilled 
...do.... 
8 © 
1,540 
A 
1,950 © 
1,985 
1,825 
495 
Double disked 
do 
...do.... 
8 © 
1,405 
(i) 
710 © 
855 
990 
905 
Spring plowed 
Broadcast 1 - . 
June 16. 
6 
1,760 
1,880 ... 
1,820 
Double disked... 
do.i 
Drilled » .... 
...do.... 
...do.... 
6 
6 
1,780 
890 ... 
1,335 
2,320 
Spring plowed 
2,220 
2,420 ... 
Double disked 
do.i 
...do.... 
6 
2,590 
1.200 ... 
....... 
1,895 
1 Used as checks for the two methods of preparation and of seeding, respectively. 
H'ln these experiments, as in those just described, there was a small 
increase in yield for drilled plats over broadcast plats at each depth of 
submergence. However, the differences are small in most instances. 
In irrigating and draining to germinate the seed it was difficult, when 
