30 
BULLETIN 1387, U. S. DEPARTMENT OF AGRICULTURE 
Table 17. — Yields of 14 varieties of rice following green-manure crops at the Bigg 
Rice Field Station in 1924 
C. I. 
No. 
Acre 
yields (pounds) 
Type, group, and variety 
Bur-clover 
land 
Mung- 
bean and 
soy bean 
land 
Difference 
in favor of 
bur-clover 
land 
SHORT GRAIN 
Early group: 
3,960 
4,224 
4,504 
5,676 
5,412 
5,280 
5,082 
4,719 
4,719 
4,488 i 
4,389 ! 
4,075 
3,729 
5,049 
1, 996 
2, 3 13 
2,442 
2, 673 
2,920 
3,333 
3, 163 
2,937 
2,788 
3,102 
3,234 
3,795 
3,217 
2,475 
1, 964 

1,881 
Colusa 
Mid-season group: 
Selection No. 170 
Kokuryo-Miyako 
Caloro 
Selection No. 218 . 
1600 
2329" 
1561-1 
2,062 
3,003 
2,492 
1,947 
1,919' 
Selection No. 233 
1,782 
Selection No. 129 
1,931. 
Selection No. 171 _. . . 
1,386 
Selection No. 214.. 
1,555 
Selection No. 138 
280 
Selection No. 139.. 
512 
LONG GRAIN 
Earlv group: Nelson. 
2,574 
Average 
4,665 
2,887 
1,778 
.^The increase in yields on bur-clover land range from 280 pounds 
per acre for Selection No. 138 to 3,003 pounds for Selection No. 176. 
The average increase for all varieties was 1,778 pounds per acre, or 
38 per cent. 
The yields obtained on the mung-bean and soy-bean land were but 
little, if at all, higher than are usual on ordinary fallow. This may 
have been due to the nitrogenous organic matter plowed under in 
November having been nitrified during the fall and winter months, 
the nitrates thus formed then being leached from the soil by spring 
rains and irrigation water preceding submergence and so lost for 
crop use. The bur-clover crop, on the other hand, was not plowed 
under early enough to permit rapid nitrification, due to the dry soil, 
and as a result the nitrogenous organic matter probably decomposed 
during the growing season and the nitrogen compounds formed as a 
result of this decomposition under water were in a form most avail- 
able for the rice crop. At any rate, the result was a material increase 
in yields. 
These results, although not necessarily conclusive, indicate that 
deficiency in available nitrogen is the factor which limits rice yields 
on the soil of the station farm. The data show that yields can be 
increased materially when rice is grown after a winter leguminous 
green-manure crop. The problem is to find a suitable legume which 
can be grown as a winter crop on the old rice lands for green-manure 
purposes. The use of nitrogenous fertilizers also may prove profitable 
in many cases. 
^NURSERY EXPERIMENTS: 
A large number of bulk varieties of rice fronf various countries, as 
well as many selections made from these bulk varieties, have been 
grown in the nursery experiments at the station. These varieties and 
selections have been grown in rod rows spaced 3 feet apart. The 
