44 CONTROL SERIES No. 72 



Laboratory and Field Germination Tests of Sweet Corn 

 Seed Laboratory, Departments of Botany and Vegetable Gardening Cooperating 



The purpose of this project is two-fold: First, to compare germination results 

 obtained in the seed testing laboratory with those obtained in the field, in order 

 to evaluate the relation between field and laboratory testing of sweet com, so that 

 from careful observation of the laboratory germination test one may be able to 

 predict the field performance of the same seed; and second, to determine the kinds 

 of disease organisms that occur in commercial lots of sweet com and their effects 

 upon germination both in the laboratory and in the field. Official rules for seed 

 testing were followed in making all tests. 



In the laboratory the rag-doll method was used; that is, the seeds were placed 

 between folds of moist paper toweling, rolled up, and wrapped in a sheet of oiled 

 paper. Tests were alternated between germinators which are kept at constant 

 temperatures of 20° and 30° C. They were allowed to remain in the 30° oven for 

 a period of 8 hours and then placed in the 20° oven for 1 6 hours. Preliminary counts 

 of the germinated seeds were made after tests had been in the ovens 3 days, a sec- 

 ond record taken after 5 days, and a final one at the end of 8 days. Some varieties 

 of sweet corn germinate much more quickly than others, but 8 days seems to be 

 the maximum requirement for most varieties. During the 1933 season 200 seeds 

 each of 253 samples were tested. Three divisions were considered in the germina- 

 tion readings: Normal sprouts, abnormal seedlings, and dead or otherwise non- 

 viable seeds. To be called normal a seedling must have produced a strong plumule 

 and a vigorous root system, it must be apparently disease-free, and the root and 

 shoot must be of good measure, depending upon the variety of com. Seedlings were 

 classed as abnormal because of weakness as shown by slow development or efTect 

 of disease. All tests were critically examined and records kept of percentages of 

 normal and abnormal seedlings, as well as of the kinds and percentages of disease 

 present in each lot. 



Field plantings were made in carefully prepared soil, 200 seeds of corn being 

 planted from each sample that had been tested in the laboratory. The soil was 

 rather moist and heavy, and the temperature was cool during the test period. 

 Preliminary counts of plants were made at the end of 2 weeks. After 4 weeks the 

 plants were removed from the soil and final observations recorded. Normal and 

 abnormal plants were counted. All plants were inspected for disease and findings 

 carefully tabulated. 



The following is a summary of the results, with interpretations. 



1. Number of seed lots germinated in the laboratory and in 



the field 253 



2. Germination in the laboratory (average of all lots) Pet Cent 



a. Abnormal due to diseased roots or shoots 8.9 



b. Abnormal due to other causes 2.7 



c. Dead or otherwise non-viable seeds 6.5 



d. Normal germination 81.9 



3. Total emergence in field (average of all lots) 71.3 



a. Weak and diseased seedlings 0.7 



b. Normal germination 70.6 



The probable reasons why the laboratory germination was higher than the field 

 germination are: First, laboratory conditions of moisture and temperature are 

 nearer the optimum requirements for germination than field conditions; second, 



