No. 570] 



ALFALFA BREEDING 



359 



That the relative humidity had little to do with yield is 

 shown by the fact that the highest averages for this factor 

 occurred on the first and fifth cuttings which were the 

 highest and lowest in yield, respectively. 



Although it was intended to give each plot approxi- 

 mately the same amount of water for each cutting, uneven- 

 ness in the slope made this impossible. The average 

 amount of water applied to each cutting was 6.28 inches 

 with an average standard deviation of 1.54 inches. Now, 

 taking cognizance of this variation in the water supply, 

 we find that its effect upon the yield was only appreciable 

 in the fourth and fifth cuttings. Eecords were not made 

 of the water supplied to the first cutting, but after that 

 time they are complete. By reference to Table II it will 

 be observed that these correlations in the second, third 

 and sixth cuttings are so small as to be negligible, but in 

 the fourth and fifth cuttings they are sufficiently large to 

 indicate that this factor was of some importance in gov- 

 erning the yields. These results may be interpreted as 

 meaning that approximately 6.28 inches of water were 

 ample for each cutting during the cooler weather of spring 

 and fall. That too much was not given at these seasons, 

 however, is shown by the absence of large minus correla- 

 tions. Factors other than water supply, therefore, gov- 

 erned the yields during these periods. Hot, dry weather 

 came on during the growth of the third cutting, but the 

 amount of water supplied plus the winter and spring sur- 

 plus left in the soil was ample to mature the crop. With 

 the continued high demand for water during the hot 

 weather of July and August, the surplus having been 

 exhausted and the summer rains helping but little, six and 

 one fourth inches was not sufficient. There was, therefore, 

 marked suffering for water, which was reflected in the 

 yields of those plots that received slightly more or less of 

 irrigation than the others. 



It would seem, therefore, that high temperature and a 

 slight deficiency of water were the disturbing factors in 



