On the Chemical Properties of Soils. 



Experiment. 



1st. Hemoved by 7000 grains of water 



2nd. 



3rd. 



4th. 



5th. 



6th. 



7th. 



Total 



Ammonia. 

 Grains. 



236 

 642 

 610 

 622 

 120 

 193 

 228 



. 2-651 



Thus '2651 grains of ammonia were removed by 49,000 grains 

 of water from J Ib. of soil. This quantity of soil absorbed 

 from a strong ammoniacal solution 4 '655 grains of ammonia. 

 By deducting 2'651 grains of ammonia, i. e. the amount washed 

 out by seven successive washings, with 7000 grains of water each, 

 we obtain 2'004 as the quantity of ammonia which was retained 

 by the soil, after all the washings with water. 



More than half the ammonia originally absorbed by the soil 

 was thus again removed by washing with water. 



It appears thus distinctly that the power of soils to remove am- 

 monia from solutions is very much greater than their property of 

 yielding it again to water. 



Indeed even a very much larger quantity of water than that 

 which falls annually upon our fields in the shape of rain is 

 incapable of washing out of the soil such a proportion of am- 

 monia, as can be of any account in relation to the quantities 

 incorporated with it in the shape of natural or artificial manures. 

 In the experiments before us the weight of water which was 

 passed through the soil was twenty-eight times as large as the 

 weight of the soil, and yet little more than half the quantity 

 of ammonia absorbed by the latter was extracted by this 

 immense amount of water. In nature such excessive washings 

 by rain are not likely to occur ; we need not therefore fear that 

 the ammonia absorbed by the soil we cultivate will be removed 

 by the most heavy rain-storms to anything like the extent in 

 which it was removed in my experiments. 



At the same time it is well to remember that each shower of rain 

 renders soluble some ammonia which may have been previously 

 absorbed by the soil. The best fertilizing matters, if presented 

 to plants in great abundance, exercise an injurious effect upon 

 their growth, or, at any rate, favour an unhealthy development 

 of one part of the vegetable organism at the expense of another. 

 Thus wheat or barley grown on a dung-heap becomes rank and 

 attains a great size, but will hardly flower, and never produce any 

 grain. This is accounted for by the fact that farm-yard manure 

 contains far too much soluble manuring matters to be beneficial 

 to the healthy development of the crops which we cultivate. 



