238 MASS. EXPERIMENT STATION BULLETIN 271 



stitution. All the experiments thus far indicate that lime is indispensable 

 for successful onion production on the soils of the Connecticut Valley. 



In the old fertilizer ratio series, the 4-12-8, which has led in former 

 years, was inferior to the 4-8-4 and about equal to the 4-8-8. (Figures 

 refer to percentages of NH3 (old basis), PiOs, and K2O, respectively.) The 

 highest yield was from the 4-8-4 with later side dressing of nitrate of soda 

 e(!uivalent to a 2-0-0, and the lowest from 2-12-8. It is quite possible that 

 the substitution of sets for seed influenced the effect of fertilizers. The 

 4-7-4 with a side dressing of fish (2-1-0) gave a low yield. These results 

 with additional nitrogen as side dressing are similar to those of last year, 

 but cannot be explained in the same way; last year was unusually dry, 

 while in 1930 the rainfall during the growing period of the onions (sets) 

 was slightly above normal. In the lime series the 4-12-8 was superior to the 

 4-8-4, and in the old cover crop series the 4-12-8 was superior to the 

 G-8-8. Considering the results of this experiment for the six years of its 

 duration, it would seem that for land which has not been intensively fer- 

 tilized for several years previously, a fertilizer high in prosphoric acid 

 and potash, something like a 4-12-8, is needed for at least the first several 

 years of onion growing. Fertilizer has been applied at the rate of 2500 

 pounds per acre, a comparatively high rate, and it is quite probable that 

 a cumulative effect of previous years is beginning to manifest itself. 



A field experiment with onion sets of three size groups demonstrated the 

 superiority of sets of medium size. Sets from one-half to three-fourths inch 

 in diameter yielded almost twice as much as those one-fourth to one-half 

 inch, and slightly more than those three-fourths to one inch. The medium 

 group threw less than 1 per cent seed stalks, the large sizes 72.9 per cent, 

 and the smallest none. The largest sets produced 33.0 per cent multiple 

 bulbs, medium sets 1.4 per cent, and smallest sets 0.12 per cent. About 

 three times as many bushels were required to plant an acre with large 

 sets as with medium-sized sets. Altogether, the results were strikingly in 

 favor of medium sets. 



Onion breeding work was continued on lines previously described. 



Nitrogen Assimilation by Tobacco^ (A. B. Beaumont and G. Rohde). 

 Further evidence has been secured from solution cultures which supports 

 statements made in the last report that nitrogen in the form of nitrates is 

 better assimilated than in the form of ammonia, urea, and certain organFc 

 forms. This nutritive relation prevails when the entire growing period of 

 the plant is considered, although there api)ear to be stages of growth when 

 ammonia is assimilated as well as nitrate, if not better. 



Field Experiments with Tobacco. (A. B. Beaumont and M. E. Snell). 

 1930 has been the best year for the growth of tobacco since the field ex- 

 periments were started seven years ago, with the best plots producinjr 

 slightly more than 1 ton of cured leaf per acre, and all plots averaging 

 around 1800 pounds per acre. The highest yield, averaging 1998 pounds 

 per acre, was from a series of 10 plots which received 262.5 pounds of 

 tobacco fertilizer analyzing 4.1 per cent N, 4.0 per cent PlO-., and 5.0 per 

 cent K.O, and 10 tons of manure. Five plots which had a cover crop of 

 redtop were next with an average yield of 1936 pounds, followed by those 

 which had timothy and rye as cover crops. .\s in previous years, tobacco 

 yields were poorest in the animal husbandry rotation (corn, timothy or 

 clover, and tobacco), yields being 1201 pounds after timothy and 1326 



