802 



Journal of Agricultural Research voi.xx, no. 



Table III. — Temperature indices in relation to ripening of sweetcorn 



EXPONENTIAL INDICES AS A BASIS FOR AN APPROXIMATE PREDIC- 

 TION OF THE RATE OF RIPENING IN SWEETCORN 



Since the rate of ripening appears to be inversely proportional to the 

 exponential indices, the proportions 



6 : x : : y : 5. 3020 

 2 : x : : y : 5. 3020 

 furnish a basis for an approximate prediction of the number of days in 

 different localities and for different seasons in the same locality required 

 for corn to pass from the premilk stage to the best edible milk stage, 

 and also the maximum number of days that the corn may be expected 

 to remain in this condition. The first term of the first proportion is the 

 number of days actually required for an early crop to pass from the pre- 

 milk to the best edible stage, or from a starch content of about 2.4 per 

 cent to one of 11 per cent. The first term of the second proportion is 

 the maximum number of days that the corn of the early crop here con- 

 sidered remained in the best edible condition. The last term of the 

 proportions is the average of the exponential indices corresponding to 

 the daily mean temperatures for the 6-day period. By substituting for 

 y in these proportions the average of the exponential indices derived from 

 the normal daily mean temperatures for any season of any locality, the 

 value of x in the first proportion gives the approximate number of days 

 on the average that will be required for the corn to pass from the pre- 

 milk to the best edible condition. The value of x in the second propor- 

 tion gives the number of days that the corn may be expected to remain 

 in this condition. 



Table IV gives the values of x for the usual ripening seasons of 

 four sweetcorn localities which show considerable variation in the normal 

 mean temperature for the ripening periods. In this calculation, the 

 normal mean temperatures calculated by Bigelow 1 were employed. 



1 Bigelow, F. H. the daily normal temperature and daily normal prectpitation op the united 

 states. U. S. Dept. Agr. Weather Bur. Bui. R, 186 p. 1908. 



