Alfalfa Seed Production 
9 
half of the rows are suffering for the need of moisture, while in the up¬ 
per half the rows can hardly be distinguished, due to the rank growth 
resulting from the subsoil moisture. 
The dry portion of this nursery has been divided into three dif¬ 
ferent parts, each portion to be irrigated with a different amount of 
moisture. 
Before irrigating, moisture determinations were made for each 
foot in depth in the moist, and dry portions of the plat, with the fol¬ 
lowing results of moisture percentages based on the dried soil samples: 
AMOUNTS OF MOISTURE IN MOIST AND DRY PARTS OF ALFALFA PLAT. 
1 ft. 
2 ft. 
3 ft. 
4 ft. 
5 ft. 
6 ft. 
7 ft. 
8 ft. 
9 ft. 
10 ft. 
Per 
Per 
Per 
Per 
Per 
Per- 
Per 
Per 
Per 
Per 
cent 
cent 
cent 
cent 
cent 
cent 
cent 
cent 
cent 
cent 
Moist part. . 
. . 7.9 
7.5 
6.1 
5.1 
5.3 
6.0 
7.0 
7.6 
10.3 
11.8 
Dry part. . . . 
. . 5.3 
4.5 
3.9 
3.8 
4.1 
5.0 
5.5 
5.6 
5.1 
7.7 
Gravel was encountered at ten feet under the dry portion, and was 
not encountered under the moist part of the plat. 
It will be observed that in both portions of this plat the soil 
is driest from three to six feet in depth. It is evident that the plants 
have made their growth from the precipitation at the surface, and 
from the deep subsoil moisture through their long roots that were de¬ 
veloped when irrigation kept the whole subsoil moist, as rootlets were 
encountered to the depth of ten feet. More extended investigations 
will be necessary before drawing definite conclusions. But these tests 
suggest two reasons why alfalfa growing on deep subsoil moisture 
might fail to set seed well. First, when the plants are in full bloom 
and forming seed there is an extra demand for moisture that may not 
be supplied fast enough through the long roots passing through the 
dry surface soil, consequently the flowers “blast”. Second, owing to 
the fact that the plants are deriving most of their nourishment from the 
deep soil areas, it may be that the failure to set seed is due to the 
availability of food constituents in the subsoil or to the absence of some 
constituent. 
* \ 
Controlling Moisture for Seed Production. 
The usual attempts to regulate moisture for seed production are 
fruitless of results because the ordinary methods of growing alfalfa 
for hay are inadequate for the purpose of seed production. 
Thick Seeding .—The method of seeding alfalfa thickly, either by 
drilling or broadcasting, is admirably suited to the production of fine 
hay, but is not suitable for the production of seed. The stems growing 
thickly, fine and succulent are more likely to “lodge” with wind or rain, 
and the flowers are borne principally on the tips of the plants due to 
the overcrowding. In a very thin stand of alfalfa the stems grow 
more branched and stocky, the flowers are produced in greater profu¬ 
sion over the whole plant and are more inclined to set seed. 
