144 



Bulletin 394 



there is a difference due to time of harvest. Therefore, the averages 

 of the results obtained for the different periods are listed, with their 

 probable errors computed according to Peter's formula. For the four- 

 months period the results of both years are included. The figures are 

 given in table 10. 



From this table it is evident that the fiber content was least at the 

 end of the first period of growth. There was also a small decrease during 

 the last period as compared with the second. While this may not be a 

 general characteristic, that it did obtain under the conditions of these 

 experiments was indicated by cultural observations as well as by analysis. 

 It may be concluded that from the standpoint of fiber content there is 

 no disadvantage in allowing sweet clover to grow for the four-months 

 period before turning it under for green manure. 



Rate of decay 



The variations in the values tabulated as a result of the nitrate deter- 

 minations make evident the necessity of computing probable errors before 

 discussing these values. A statistical study of nitrate formation, made 

 up from the data listed in tables 4, 5, and 7, is given in table 11. For 



TABLE II. Statistical Study of Nitrate Formation 



Treatment 



Unlimed 



Unlimed 



Slaked lime 



Slaked lime 



Ground limestone . 

 Ground limestone . 



Unlimed 



Unlimed 



Slaked lime 



Slaked lime 



Ground limestone . 

 Ground limestone . 



Unlimed 



Unlimed 



Slaked lime 



Slaked lime 



Ground limestone . 

 Ground limestone . 



Duration 



of growth 



(days) 



89 



89 



89 



89 



89 



89 



118 



118 



118 



118 



118 



118 



116 



116 



116 



116 



116 



116 



Treatment 



of crop at 



tiarvest 



Removed. . . . 

 Turned under 

 Removed .... 

 Turned under 

 Removed .... 

 Turned under 

 Removed. . . . 

 Turned under 

 Removed .... 

 Turned under 

 Removed .... 

 Turned under 

 Removed .... 

 Turned under 

 Removed .... 

 Turned under 

 Removed .... 

 Turned under 



Mean gain 

 in nitrates in 

 four months 



None 

 None 



None 



74 



51 



160 



13 



85 



83 



230 



54 



± 



± 

 ± 

 ± 

 ± 

 ± 



12 



8 



16 



8 



24 



2 



38 

 10 



274 ± 25 



16 



32 



37 

 244 



45 

 226 



± 

 ± 

 ± 



± 

 ± 



o 



8 



5 



25 



o 



5 



Net gain 

 due to crop 

 turned under 



None 



74 ± 12 3 

 109 ± 18.0 



72 ±25.4 

 147 ± 38.6 

 220 ±27.9 



16 ± 8.9 

 207 ±26.4 

 181 ± 5.6 



I 



a given pot the nitrates at harvest were subtracted from those found after 

 four months. The values obtained for each pair of pots treated alike 

 at harvest were averaged, resulting in the column headed Mean gain in 

 nitrates in four months. Next, for a given treatment as regards liming, 



256 



