g2 MANURES. 



original liquid, no less than eighty-one grains have been retained 

 by the soil. This is a result of the greatest importance, inasmuch 

 as it shows that the soil possesses, in a remarkable degree, the 

 power of removing from highly mixed manuring substances, not 

 only ammonia from ammoniacal salts, but also the no less impor- 

 tant soluble potash compounds. -According to this result, 1,000 

 grains of soil absorb no less than 2,313 grains of carbonate of 

 potash. 



But, in addition to carbonate of potash, a considerable quantity 

 of chloride of potassium is retained in this soil by passing the 

 washings from rotten dung through it ; for it will be observed that 

 nearly nine grains of this salt, or, in exact numbers, 8.81, were re- 

 tained in the soil. 



The avidity of the soil for soluble salts of potash is the more 

 remarkable, as it offers a striking contrast to the apparent indiffer- 

 ence in this soil to absorb soda from its soluble combinations ; for 

 it will be seen that the liquid, after filtration through the soil, con- 

 tains only about four grains less of common salt in the gallon than 

 before filtration. 



In a purely chemical point of view, soda salts are closely allied 

 to salts of potash, and yet there is a marked difference observable 

 in the power of this soil, at least, to absorb the one or the other 

 alkali. 



As regards the practical effect which salts of soda and potash 

 are capable of displaying with reference to the nutrition of plants, 

 the former are not to be compared to the latter in point of eflScacy. 

 It was believed at one time that soda was capable of replacing 

 potash in the ashes of our crops, but this opinion was not based on 

 trustworthy evidence. On the contrary, the best and most exten- 

 sive series of ash analyses of our crops show that while the amount 

 of potash, within certain limits, is constant in the ashes of plants, 

 that of soda, especially of chloride of sodium, is liable to great 

 fluctuations, arising, no doubt, from local conditions of the soil. 



The fact that soils are capable of absorbing potash from soluble 

 manurirg matters, while no special care is manifested by them to 

 retain the equally soluble soda salts, appears to rac to account, to 

 some extent at least, for the comparative constancy of the amount 

 of potash in the ashes of our crops, as well as for the fluctuations 

 of the amount of soda in the same. The power of soils to retain 

 potash in large proportions must have the effect of converting the 



