26 



THE WEED FACTOR IN THE CULTIVATION OF CORN. 



cent for the third group. These results are shown in Table VI, and 

 they seem to indicate that when for any reason the uncultivated plat 

 falls below the cultivated plat in yield the uncultivated corn has a 

 tendency to mature earlier than the cultivated corn. 



Table VI. — Relative time of maturity of cultivated and uncultivated corn. 



Relative time of maturity. 



Cultivated ripened first 



No difference in time of ripening 

 Uncultivated ripened first 



Total 



Number of experiments. 



1909 



1910 



1911 



Total. 



3 

 11 

 3 



18 

 9 







10 



10 

 39 

 19 



17 



34 



17 



68 



Average 

 grain 

 yield of 

 unculti- 

 vated ex- 

 pressed 

 as percent- 

 age of cul- 

 tivated. 



100.36 

 101. 68 

 95.58 



RELATION OF CORN-TILLAGE RESULTS TO RAINFALL. 



In the annual charts of the experiments, with the exception of the 

 year 1911, for which the data are not yet available, are given the 

 actual rainfall, the mean rainfall, and the actual rainfall expressed 

 as a percentage of the mean. As previously stated, this rainfall is for 

 the last three months of the previous year and for the first nine 

 months of the year in which the experiment was conducted. Rain- 

 fall data are available for 95 of the 124 experiments. Of the whole 

 series of experiments the lowest rainfall with reference to mean was 

 42 per cent and the highest 133 per cent. In two experiments a rain- 

 fall of over 120 per cent of the mean was recorded, while in three 

 experiments the rainfall was less than 60 per cent of the mean. 

 Working out the relation between the yield of the uncultivated plats 

 expressed in percentage of the yield of the cultivated plats and the 

 rainfall expressed in terms of percentage of the mean rainfall, there 

 was found to be a correlation of only 0.142 ±0.065, which can not be 

 considered significant. 



In actual rainfall the lowest precipitation for any experiment was 

 16 inches for the year and the highest 61 inches. The greater number 

 of the experiments upon which rainfall data are presented received 

 from 30 to 40 inches of rain for the period. Working out the corre- 

 lation between the yield of the uncultivated plat, expressed in per- 

 centage of the cultivated, and the actual rainfall, there was found to 

 be a correlation of only 0.0188 ±0.067. 



These data do not indicate that rainfall enters into the problem 

 to any appreciable extent 



