GROWING ALFALFA SEED. 451 
A hundred plants may be counted off and tripped by hand three 
times a week during the blooming period, using either of the 
methods previously described. Another hundred plants of similar 
seeding habits should be left to be exploded by insects. Any 
greater production of seed on a given number of heads on the 
manipulated plants as compared with the same number of heads 
on those not so manipulated may with reasonable safety be at- 
tributed to artificial tripping. 
If the increased yields which have been obtained in the pre- 
liminary experiments are equaled in seed-producing sections, it is 
probable that means will be devised for exploding the flowers on 
a large scale. The only sections in which this method will be 
likely to prove profitable are those where for any reason proper 
insects are not present in sufficient numbers to explode a large 
percentage of the flowers. 
Areas Adapted for Seed.—The experiments thus far carried out 
in the production of seed in cultivated rows have been located 
principally in the semi-arid portions of the Great Plains, in the 
intermountain area, and in the Palouse country of eastern Wash- 
ington. It is probable that the method will be found to be 
adapted to many of the semi-arid sections of the country which 
have a rainfall of from 14 to 20 inches, and possibly also to irri- 
gated sections where the supply of water is insufficient for the 
production of full hay crops. It is also recommended for trial 
in irrigated sections having water for but half or less of the nor- 
mal acreage of alfalfa in the district, and also for fields lying 
slightly higher than the ditch lines, but which have the water 
level moderately near the surface. 
Experiments in humid sections indicate that even there row 
cultivation makes possible much higher yields of seed than are 
produced by fields sown broadcast or drilled in the ordinary 
manner. It is doubtful, however, whether even this method will 
insure the production of paying crops of alfalfa seed under humid 
conditions. 
Row cultivation under conditions of ample rainfall is more 
valuable as a method of weed control than for increasing seed 
yields. At the time when pod formation is going on, a certain 
amount of dry weather and heat is necessary to insure the great- 
est production of alfalfa seed, even when the plants are isolated. 
This method promises to be more successful in sections where the 
annual rainfall is from 14 to 20 inches than elsewhere. Where 
the precipitation ranges from 20 to 25 inches thin seeding by 
broadcasting or drilling in the ordinary way may be preferable 
to row cultivation. Fields sown by either of these methods can 
