Importance of Nitrogen to Growth of Plants. 



237 



produced on the weed plats was much less than where cultivated in the 

 usual way. It will also be seen that the percentage of moisture was 

 only slightly less on weedy than on cultivated plats. Does it follow, 

 then, that the yield of maize was not influenced by the need for moisture 

 or was the growth of the maize checked by the diversion of some of the 

 water from the maize to the "weeds?" Manifestly the weeds required 

 some water to produce them. If this water had not been employed in 

 producing weeds, would it have been raised in producing maize? It 

 seems almost impossible to plan an experiment which will directly answer 

 this question, since we do not know the relative evaporation of the 

 relative run ofif from cultivated soil as compared with soil covered with 

 weeds. There would seem to be two reasons, however, for believing 

 that while the available water may have been a factor in checking the 

 growth of maize there must have been some other influence, also. First, 

 the total product produced was not as great on the weedy plats as on 

 the cultivated plats; and, second, it is entirely probable that in a dry 

 season all the plats would have had a lower percentage of moisture and 

 yet the cultivated plats would have produced more maize than the weedy 

 plats produced this year. 



The following table gives the water-soluble nitrogen (NO3) in parts 

 per milHon of dry soil on the cultivated plat 461 and on the millet plat 

 462 at dates mentioned and plat 462N to which nitrate of soda was 

 applied as explained hereafter: 



Table X. Variations in Water-Soluble Nitrogen. 



May 31 . 

 June 1 1 . 

 June 22 . 

 July 2 . . 

 July 8 . . 

 July 19. 

 July 30 . 

 Aug. 16 . 

 Aug. 2 1 . 

 Aug. 29. 



56-4 

 80. 



73-9 



96. 



68.5 



52.7 

 12.3 



26.0 



10.5 



6.2 



21.8 

 48.0 



160.0 



320.0 



218.2 



282.5 



up to June 22 no difference in the growth of maize could be ob- 

 served which could be attributed to the weeds. On July 2, however, a 

 difference in the color of the maize upon the millet plat was plainly 

 observable. The millet was about as high as the maize. Hosford further 

 reports that the maize was about the same size on both these plats on 



