CUM A TIC REQ UI RE ME NTS 3 7 



An American writer points out that the curling of the chap. 

 leaves of the maize plant in July (equivalent to January in IL 

 South Africa) is a bad omen to maize-growers in the drier 

 districts. The time of the formation of the ear (January and 

 February) is the critical period in the life of the plant, and 

 lack of moisture at this time means curtailment of yield 

 (Bowman and Crossley, 1). 



29. Rainfall. — Though no direct relation exists between 

 actual temperature and yield, rainfall, on the contrary, has a 

 very direct bearing upon yield. 



At the Illinois Agricultural Experiment Station a rainfall 

 of 13 inches during the five growing months, produced 

 1,792 lbs. (practically 9 muids) of dry maize-grain per acre. 

 The following year, with 22-5 inches during the same period, 

 the yield (without fertilizer) was 5,264 lbs. (over 26 muids) 

 per acre. The mean temperature was more favourable the 

 first season than the second. The results indicate that the 

 increase of 17 muids per acre was due to the additional 95 

 inches of rain, an average of 1-9 inches per month. 



In the Corn-belt of the United States the most favourable 

 condition is found to be a series of comparatively heavy rains 

 during the growing season, but at considerable intervals, with 

 clear sunshiny weather between, and followed by a warm, 

 dry, ripening period. If the rainfall equals 1 1 '5 to I2'0 inches 

 in the three summer months corresponding to December, 

 January, and February in the Southern Hemisphere, this 

 should be adequate; of this, 4-5 to 5 'O inches should fall in 

 January, when the ears are growing most rapidly. The aver- 

 age rainfall for these three months for thirty-nine stations 

 through the Maize-belt of South Africa is 11-92 inches, while 

 the average for January is 4-35, or 4-6 if we omit the three 

 driest localities, which are really outside the Maize-belt. 

 Heavy rainfalls and cloudy weather during the planting season 

 (corresponding to October and November in South Africa and 

 South America) are in North America found to decrease 

 the yield. In South Africa a wet October and November 

 prevents proper weeding and encourages early growth of weeds 

 which withdraw moisture and plant-food from the young 

 maize plants, thereby reducing the yield. But excess of 

 moisture, as already explained (IT 27), is injurious. 



