4 MASS. EXPERIMENT STATION BULLETIN 318 



Since that time the acreage of onions grown from sets has increased rapidly, and 

 largely at the expense of the acreage grown from seed. Recently the acreage of 

 "set" onions has exceeded that of "seed" onions. Reasons for this shift were 

 earliness for market and greater chance of securing a good crop by avoiding 

 attacks of thrips and the often disastrous effects of "blast" and downy mildew. 



Among the practical problems facing the grower of onions in the Connecticut 

 Valley when the experiments reported in this bulletin were started were some 

 related to production. These included the use of lime, the choice and method of 

 applying fertilizers, value of cover crops, spacing, growing of sets, and improve- 

 ment of onions by breeding and selection, as well as diseases and insect pests. 

 The results of experiments concerned with these problems are reported in the 

 following pages. 



EXPERIMENTS WITH FERTILIZERS FOR ONIONS » 



Soil Conditions and Plan 



These experiments were conducted on an alluvial soil classified as Agawam 

 fine sandy loam. It has a brown surface soil and a light brown, yellow or gray 

 subsoil. This soil type has a rather uniform texture to a depth of three feet or 

 more, is comparatively free from stones, has a level to slightly rolling topography, 

 and poor to fair natural drainage. The drainage of the experimental field was 

 improved by a system of tile drains installed prior to the beginning of the ex- 

 periment. The organic matter content of the soil at the beginning of the experi- 

 ment was 5.9 per cent and the reaction was pH 5.3. It contained 8.2 per cent 

 clay, 58.4 per cent silt, and 33.4 per cent sand. In practically all respects except 

 content of organic matter, which was slightly higher than that of most onion soils 

 of the Connecticut Valley which have grown onions a number of years, this soil 

 is typical of the onion soils of this region. 



During the 20-year period preceding the experiments reported herein, the 

 experimental field was in pasture most of the time, but corn was grown for two 

 years immediately preceding the beginning of the experiment with onions. The 

 field was seeded to mixed grasses and clovers sown in the standing corn the year 

 before starting the onion experiment. The new seeding grew well during the fall, 

 and was plowed under a few weeks before seeding onions in the spring of 1925. 

 The field was limed in 1908 and again lightly in 1922. From 1908 to 1922 little 

 or no fertilizer was applied, but a moderate amount was given the two crops of 

 corn grown in 1923 and 1924. 



The field was divided into plots having an area of approximately 1 square rod 

 each, and arranged according to the chess-board plan. Each plot was 18' 5" x 18', 

 but this allowed a border zone around each plot, leaving a harvested portion of 

 exactly 1 square rod. Plot treatments were replicated a minimum of 4 times 2 , 

 but, as indicated later, some treatments, particularly checks, were replicated 

 more frequently. 



Difficulty was met in the interpretation of the data on yield, especially of 

 onions grown from seed. The "seed" crop, requiring a longer growing season than 

 the "set" crop, is particularly open to the attack of thrips and to the disastrous 



■l redit is given f"r valuable assistance rendered in the early years of the experiments by Drs. 

 I Street a rid J. P. Joi • . ai d Messrs. T. R Swanback and R. M. Home. 

 'Except the 4-7-4 treatment which was replicated 3 times. 



