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 



