RICE CULTURE IN CALIFORNIA 
21 
perjacre. The average acre yields for Wataribime show consistent 
increases with increased rates of seeding from 85 to 150 pounds per 
acre except for the 130-pound rate. For Caloro the average yield 
did not show consistent increases for increased rates of seeding. The 
highest average yields were obtained from the 175-pound and 150- 
pound rates, although that for the 100-pound rate was nearly as good. 
These results indicate that on old land rice probably should be sown 
at the rate of about 150 pounds per acre. 
The three-year average acre yield of the three varieties at all rates 
of seeding was 2,876 pounds for Selection No. 175, 2,718 pounds for 
Caloro, and 2,801 pounds for Wataribime. 
Table 12. — Yields from tenth-acre plats of Selection No. 175, Caloro, and Watari- 
bune rices grown in rate-of -seeding experiments at the Biggs Rice Field Station in 
1921, 1922, and 1923 
Acre yields (pounds) 
Rate of seed- 
Selection No. 175 
Caloro 
Wataribune 
Three-year average 
ing 
1921 
1922 
1923 
1921 
1922 
1923 
1921 1922 
1923 
Selec- 
tion 
No. 
175 
Calo- 
ro 
Watar- 
ibune 
85 pounds 
100 pounds 
115 pounds 
130 pounds 
150 pounds 
175 pounds 
1,880 
2,660 
2,710 
2,740 
3,030 
2,450 
2,450 
2,560 
2,920 
3,630 
3,510 
3,820 
2,450 
2,140 
2,650 
3,350 
3.540 
3,280 
2,380 
2,630 
2,460 
2,510 
2,860 
3,080 
2,690 
3,260 
3,170 
2,980 
3,180 
2,900 
1,650 
2,640 
2,550 
2,470 
2,600 
2,917 
2,150 
2,800 
3,210 
3,160 
3,640 
3, 290 
2,340 
2,650 
3,170 
3,160 
3,110 
2,770 
2,140 
2,310 
2,790 
2,680 
2,620 
2,420 
2,260 
2, 453 
2,760 
3,240 
3,360 
3, 183 
2,240 
2,843 
2,727 
2,653 
2,880 
2,966 
2,210 
2,587 
3,057 
3,000 
3,123 
2,827 
Average . 
2,578 3,148 
2,902 
2,653 
3,030 
2, 471 3, 042 
2,867 
2,493 
2,876 
2,718 ; 2,801 
EFFECT OF CONTINUOUS CROPPING ON RICE YIELDS 
In the older rice-producing countries of the world rice is reported 
to be grown on the same land year after year. If this is a common 
practice there is little doubt that every available means is utilized to 
maintain and if possible increase the fertility of the soil. The use of 
manure, green manures, compact materials, sediment from the beds 
of streams, and commercial fertilizers when practicable is reported 
to be common on such lands. 
In California three or four crops of rice are all that usually have 
been profitably grown in succession on the same land. This is 
due largely to the fact that weeds, especially water grass, increase 
so rapidly that rice yields are seriously reduced thereby and not 
because the rice has robbed the soil of its fertility. 
Every agricultural section has its weed problems, and the solution 
is usually diversification and rotation of crops. Maximum yields 
with all cereal crops are usually obtained in rotation systems and 
not by continous cropping. The yields obtained from rice grown on 
the same land 11 of the 12 years from 1913 to 1924, inclusive, are 
presented in Table 13 and are shown graphically in Figure 5. The 
yield in 1913 was the average from 10 tenth-acre plats. Yields in 
1914, 1915, and 1916 were from 12 tenth-acre plats, and those from 
1917 to 1924, inclusive, were from 5 tenth-acre plats. 
