22 N. H. AGR. EXPERIMENT STATION. [Bulletin 11 



The summer of 1915 was very wet and as a consequence the 

 nitrates recovered in our samples were low as compared with 

 other years. This can be well seen on Charts 3 and 8, as the 

 heavy rains began July 6. The curves drop down at that time 

 and remain low throughout the rainy period without much dif- 

 ference between the plots. This is likely due to two things, first, 

 nitrification was probably not so rapid when the soil was very 

 high in moisture, and second, what nitrates were formed were 

 readily leached out. Plot 5 here fell a little below Plot 4 with a 

 difference in favor of the latter of about 2 p. p.m. 



This evidence seemed to warrant the position that the forma- 

 tion of nitrates is greatly reduced in a sod orchard and from a 

 fertility standpoint is the first limiting factor. Not only does 

 the growth average about half as great as where a good system 

 of culture is practiced, i.e., as 4.80:8.83, but also we find a smaller 

 size of the leaves and a poor color, denoting an insufficient amount 

 of available nitrogen. That the lack of vigor is due to an insuffi- 

 cient supply of moisture cannot be advanced for it has been some- 

 what of a surprise throughout the entire experiment that there 

 was a higher per cent of moisture in the sod plot than in the adja- 

 cent tilled ones. 



NITRIFICATION UNDER SOD. 



During the past season we have attempted to determine the 

 approximate amount of nitrates formed under sod. In order to 

 determine this a small plat 3 feet square was selected in Plot 1 

 (the sod plot) quite near to the point where the soil samples had 

 been previously taken, and the sod carefully removed without 

 stirring the soil beneath. Another plat of equal size was selected 

 close to the first and after the sod was likewise removed the soil 

 was spaded to the depth of the surface soil and cultivated with a 

 hoe weekly. This gave three conditions within the original sod 

 plot: (1) sod; (2) bare soil; (3) bare soil, stirred each week. 

 While the bare plat would not represent the exact conditions 

 under sod, yet it seems to be as near that condition as is practical 

 to obtain in the field. While this phase of the work was not 

 begun until the middle of summer the determinations seem to 

 throw light on the question. 



