Rice Production in Southwestern Louisiana 
21 
more land than was available. Each plat was irrigated and drained 
independently through a gate. 
Since the plats were too small to permit plowing, the land was 
spaded in winter to a depth of 5 to 7 inches and in the spring was 
thoroughly prepared by hand before seeding the crop. A good seed 
bed was always obtained. The seed was sown with a garden drill 
in rows 8 inches apart at the rate of 80 pounds per acre. The soy- 
bean rotation was not used in these experiments. 
DATE OF SUBMERGENCE 
Data showing the effect of date of submergence on yield are given 
in Table 14. The largest average yields, as shown by these data, 
were obtained on land that was submerged 15 days after the rice 
plants emerged. The average yield obtained by submergence at 
this time was 720 pounds greater than that obtained by submerging 
15 days later. With each successive later date of submergence there 
was further reduction in average yield. This reduction in yield was 
largely due to increase in weed growth. Although early sub- 
mergence has a beneficial effect in the control of many weeds, other 
experiments here discussed show that weeds can be more effectively 
controlled by growing rice in rotation with soybeans, and when this 
practice was followed submergence could be delayed 30 days after 
emergence with no apparent loss in yield. 
Table 14. — Annual and average yields of Wataribune rice obtained in the 
date-of -submergence experiments on square-rod plats at the Rice Experiment 
Station, Crowley, La., in the years 1917, 1918, and 1919 
Submergence 
Yields 
per acre (pounds) when sub- 
merged 4 inches 
1917 
1918 
1919 
Average 
2,080 
1,280 
1,840 
1,280 
1,920 
1,520 
1,600 
1,560 
4,480 
3,520 
2,240 
1,760 
2,827 
2,107 
1,893 
1,533 
DEPTH OF SUBMERGENCE 
In Table 15 are given yield data for the depth-of -submergence 
experiments for 1917, 1918, and 1919. These data show that the 
greatest average yield of rice was obtained from submerging 8 
inches, although the highest individual annual yield was obtained 
in 1919 from a 2-inch submergence. Under field conditions prefer- 
ence should be given to the deeper submergence, however, because 
it is more easily maintained. Unless the land is exceedingly level 
and the levees carefully constructed, the usual fluctuations in the 
depth of water during the period of irrigation probably would dam- 
age the crop in a submergence as shallow as 2 inches. A submergence 
of 8 inches probably is the greatest depth of water that is ever 
necessary, while a depth of 6 or even 4 inches may be sufficient on 
very level land where low levees are used, if submergence can be 
easily maintained. At the Rice Experiment Station a submergence 
of 6 inches of water is used in ordinary practice. 
Data showing the average quantity of water, including precipita- 
tion, used in the depth-of-submergence experiments during 1917, 
