Decomposition of Sweet Clover as a Green Manure 143 



Assuming that odds of 30 to i represent a chance which is practical 

 certainty, a gain must be 3.12 times its probable error to make certain 

 its significance. On this basis it is seen that the gains calculated in 

 table 8 are significant, except that for dry matter from the slaked-lime 

 pots in comparison with the unlimed pots. Here the gain falls just 

 below the value postulated to denote certainty. It is believed, however, 

 that table 8, taken as a whole, shows that the effect of lime was evident 

 during the second period of growth. 



In considering the results obtained for four months growth, tables 

 3 and 6 are available. Thus four yields for a given treatment are 

 averaged to obtain the mean. In computing the probable errors of 

 these means the same formulas were used as for table 8. The results 

 are given in table 9: 



TABLE 9. Statistical Study of Tables 3 and 6 



Treatment 



Mean grams of 

 drv matter 



(A) Unlimed 



(B) Slaked lime 



(C) Ground limestone 



Gain, B over A 



Gain, C over A 



Gain, B over C 



18.69 ± -22 

 28.61 ± 1 .80 

 26.77 ± 71 



9.92 ± I 

 8.08 ± 

 1.84 ± I 



81 

 74 

 94 



Mean grams of 

 nitrogen 



0.5743 d= .0324 

 0.9112 ± .0462 

 0.8353 ± 0148 



0.3369 ± .0566 

 0.2610 ± .0362 

 0.0759 ± 0484 



A perusal of table 9 shows that the gains due to lime are significant 

 but when the two kinds of lime are compared the difference is not 

 sufficient to allow of any conclusion. The limed crop produced, roughly, 

 50 per cent more dry matter and nitrogen than did the unlimed. 



Percentage of fiber 



A study of the tables does not reveal any differences in fiber content 

 due to different methods of treatment. It is indicated, however, that 



255 



