SEED INSPECTION 47 



Comparative Laboratory and Field Germinations of Onion Seed 

 Used for Type and Variety Studies 



In order to determine what germination may be expected of onion seeds sowed 

 in the field, compared with laboratory germination of samples of the same seed, 

 samples of each of the 124 varieties and strains of onions used for type and variety 

 studies were germinated in the laboratory and in the field, 200 seeds being used 

 for each test. 



In the laboratory two methods were employed: between blotters for 10 days 

 at 68° F.; in soil chambers containing sterilized soil for 14 days at 68° F. 



For the field tests a typical onion soil was prepared in conformance with good 

 crop practice, and the seeds were sown by hand in drills and covered with 54 inch 

 of soil. The seed had germinated suflficiently for final count at the end of 14 da^'s. 

 For the 21 days elapsing between the first sowing and the final counting of the 

 last sample sown, the mean soil temperature was 70.4° F. and the mean atmos- 

 pheric temperature was 64° F. 



Only those seedlings were counted which might be expected to produce a crop 

 of onions in the field. 



The average of all germinations was: 



Per cent 

 Laboratory tests 



In blotters 70.66 



In soil chambers 69 . 02 



Field tests 62.47 



It will be noted that there was only 1.64 per cent less germination in laboratory 

 soil chambers than in blotters. This may be accounted for because of the added 

 resistance of the soil. In the field the difference was more pronounced, bang 

 8.19 per cent less than in blotters and 6.55 per cent less than in soil chambers. 

 The difference between field germination in soil and laboratory germination in 

 soil chambers cannot be accounted for merely through a difference in soil resist- 

 ance. Some of the factors noted which were responsible for this difference were 

 erosion of the soil by rain washing out of an occasional seed, throwing out of seed 

 by worms, cutting off of seedlings by insects and fungi, burial of a seed beneath 

 lumps of hard soil or small stones, etc. Factors such as those mentioned vary- 

 greatly in different seasons and even in different fields the same season. Conse- 

 quently no figures are obtainable which will accurately represent expected field 

 germination under all conditions. Assuming, however, that all factors taken into 

 consideration during this field experiment represent the average for typical onion 

 soils in this locality for the spring of 1931, field germination was approximately 

 8 per cent less than laboratory blotter germination. 



Publication of this Document Approved by Commission on Administration and Finance 

 2500-4-'32. No. 5181 



