THE RELATION BETWEEN TEMPERATURE AND CROPS. 



DEWEY ALSDORK SEELEY. 



Temperature is one of the most iiiHuential of all the elimatie conditions 

 affecting plant growth and at tiie same time one of tlie most difficult to 

 study. Numerous investigators, beginning as far back as 1735, have 

 attacked the problem but we are still without a satisfactory statement of 

 the relationship between the air temperature and the development of a 

 single farm crop, due largely to the fact that there are so many com- 

 plicated influences involved. We do not know, for example, at what 

 temperature a crop of- wheat will thrive best, from seeding to harvest, 

 nor the number of days with a yet undetermined optimum temperature 

 for growth, that is required for the plant to pass tlirough its life history 

 To be sure tests Iiave been made in tlie laboratory on wheat, corn, etc., 

 to find the growth rate of seedlings, and the minimum, optimum and 

 maximum temperatures at which development proceeds have been deter- 

 mined. But the experiments have not been continued to cover the entire 

 life history, nor have the effects of varying insolation, humidity, wind 

 velocity, etc., surrounding tlie plant in the open, been taken fully into 

 consideration, as to their influence on temperature and growth rate. 



The fruit trees blossom in the spring after a period of warm weather, 

 and then after another period, with much more heat, the fruit comes 

 to maturit}- and ripens. But no one has yet stated the relationship 

 between the temperature of the air and either of the life processes men- 

 tioned, except in the most general terms. No one has been able to deter- 

 mine in advance before the coming of spring, how many days with given 

 ranges of temperature will pass before apples or peaches blossom. 



It is almost self-evident that an immense advantage to agriculture 

 would result if the heat requirements of various crops could be deter- 

 mined and stated in terms of air temperature and time. The problem 

 is complex and involved, as will be discussed later, but I believe it will 

 yet be solved, and that it will be possible from the records of air tempera- 

 ture in a given locality, by using certain formulae embracing correlated 

 influences, to determine definitely how nearly the optimum temperature 

 conditions are approached, in terms of percentage. It should at least 

 be possible to discover whether temperature conditions are such as to 

 prohibit tlie profitable culture of a yet unintroduced crop. If we could 



19th Mich. Acad. Sci. Rept., 1917. 



