26 MAIZE 



CHAP. It is important that we should understand the relation of 



' these several factors to the maize crop. Speaking broadly, 

 the most favourable conditions are long humid summers, hot 

 days and warm nights, comparatively heavy, intermittent rains, 

 with abundance of clear, sunshiny weather between. Hot, 

 arid climates, hot and continuously humid and shady regions, 

 and arid cool-temperate climates with short summer season, 

 are, generally speaking, unfavourable to the commercial pro- 

 duction of maize. Open plains or plateaus are therefore more 

 suitable than forest country. 



22. Altitude. — Altitude affects the growth of crops indi- 

 rectly as it influences length of season, temperature, precipita- 

 tion of moisture, depth, and richness of soil, etc. 



Evidence collected by Harshberger (i) suggests that the 

 maize plant came originally from tropical table-lands at a 

 considerable altitude, probably above 4,500 feet. 



Increase in elevation is accompanied by decrease in tem- 

 perature and a steady shortening of the summer season, until, 

 at very high altitudes, alpine conditions prevail ; long before 

 this point has been reached, however, it has ceased to be 

 possible to produce maize. Davis (1) finds that in Argentina 

 the decrease in temperature due to altitude is not a constant 

 factor but varies according to the season of the year and the 

 dryness of the air. The shortening of the season with in- 

 creasing altitude has an immediate effect upon the crop in 

 that the earliest autumn frosts, not falling regularly at the 

 same date, are apt to kill the plants before the grain is ripe 

 for harvest. The range of altitude within which a maize 

 crop can be successfully grown largely depends on latitude ; 

 the nearer the Equator the higher the altitude, within certain 

 limits, and the farther from the Equator the lower must be 

 the altitude. 



Humboldt records vast maize fields on the Mexican 

 plateau (between the 15th and 30th parallels) at 8,680 feet. 

 Near Lake Titicaca, Peru, at about the 16th degree of S. 

 latitude, maize is grown successfully at 10,000 feet. In the 

 Indian Panjab, between the 30th and 35th parallels, it is more 

 extensively grown in the hill country at 7,000 feet and over, 

 than in the valleys, where it is largely replaced by rice. In 

 Baluchistan it is grown as a regular crop at 5,000 to 9,000 



