40 BULLETIN 981, U. S. DEPARTMENT OF' AGRICULTURE. 



ing, the seed of soy beans is somewhat larger than that of cowpeas, 

 but there is a wide variation among varieties in this respect. The 

 Peking and the Arlington are two varieties which have exceptionally 

 small seed. These varieties average 6,800 seeds per pound, while 

 four other well-known varieties, Wilson, Guelph, Ito San, and Mam- 

 moth, average only 2,600 seeds to the pound. This difference in the 

 size of the seed should be taken into consideration in determining the 

 proportions of grass and legume seed. The varieties mentioned 

 above are all very well adapted for use in mixtures, because all of 

 them make a luxuriant growth of vines. 



The greatest drawback to the use of mixtures lies in the difficulty 

 of seeding the two elements uniformly. This can be accomplished 

 most easily by broadcasting the mixture. If a drill is used, great 

 caution is required to keep the Sudan grass and legume seed thoroughly 

 mixed in the drill box. Experimental plantings have been made 

 most successfully by going over the ground twice with a drill in which 

 alternate holes have been closed. In this way rows of the legume 

 can be made to alternate with rows of Sudan grass. This method 

 is too expensive, however, for extensive use by farmers. With drills 

 which have a grass-seeder attachment it is possible to run the Sudan 

 grass seed through the seeder and the cowpeas or soy beans through 

 the grain feed. 



General experience indicates that it is usually more practicable, 

 except in localities where cowpeas or soy beans succeed especially 

 well, to sow the Sudan grass an'd legumes on separate fields. The 

 greater ease of seeding and harvesting the crops is likely to overcome 

 the advantages which might be derived from a mixed seeding. 



Another feature of mixed plantings of annual crops which has re- 

 ceived little attention is the effect on the chemical composition of the 

 Sudan grass produced by its association with the legumes. Lyon and 

 Bizzell (13, pp. 365-368), of New York, found a marked increase in 

 the percentage of protein in nonlegumes when grown in association 

 with legumes; e. g., timothy with alfalfa and oats with field peas. 

 Westgate and Oakley (27), on the contrary, could detect no effect of 

 this nature. 



Table VIII. — Proportions of protein and ash in Sudan grass when grown alone and 

 when grown with legumes at the Arlington Experimental Farm in 1913. 



Crop. 



Sudan grass alone per cent . 



Do do... 



Sudan grass with cowpeas do 



Sudan grass with soy beans do 



Sudan grass with bonavist beans do 



Average, Sudan grass alone do 



Average, Sudan grass with legumes do 



Ash. 



6.63 



7.46 



6.59 



7.56 



6.40 



8.60 



7.30 



10.46 



7.66 



9.11 



6.61 



7.51 



7.12 



9.39 



