16 Liquid Manure. 



Noticing the chief points of interest that attach to these 

 results, I would direct attention to the following particulars : 



1. It will be seen that this sandy soil possessed in a very weak 

 degree the power of absorbing ammonia from liquids. Thus, 

 1 gallon of liquid, after having remained in contact with soil for 

 24 hours, only contained 2*43 grains less ; or, in round numbers 

 2^ grains less of ammonia. This small quantity, it will be 

 remembered, is removed by 20,000 grains of soil ; 1000 grains 

 consequently absorbed only '121 of a grain of ammonia. In this 

 particular this soil offers a striking contrast to the soils used in 

 the preceding experiments, which absorbed about 6 times as much 

 ammonia. 



2. The proportion of organic matter in the filtered liquid is a 

 little larger than in the original liquid ; but no appreciable differ- 

 ence exists in the amount of nitrogen in the organic matter before 

 and after filtration through the soil. 



3. In passing through the red-coloured sandy soil, the liquid 

 manure took up an appreciable quantity of oxide of iron. In all 

 probability the oxide of iron was united with an organic acid, or 

 with organic matters similar in character to the organic matters 

 found in bog-iron ore. 



4. The soil used in this experiment, it will be remembered, 

 contains a good deal of soluble silica. Liquid manure in con- 

 tact with it appears to dissolve an appreciable quantity of soluble 

 silica. 



5. In the two preceding experiments we have seen that liquid 

 manure kept in contact with soil becomes much richer in lime. 

 But in the case of the sandy soils, instead of lime being taken up 

 by the liquid manure, a considerable quantity of the carbonate of 

 lime contained in the liquid used in the experiment was actually 

 removed by the soil. The amount of lime in this soil is evidently 

 insufficient to supply the wants of the crops we cultivate on the 

 farm ; it is therefore fortunate that a soil thus constituted pos- 

 sesses the power of depriving manuring mixtures of those con- 

 stituents which are required in considerable quantities for sustain- 

 ing a healthy growth of plants. This property of soils to store 

 up food for plants is not confined to one particular kind of 

 fertilizing matter, but it applies to them all, and manifests itself in 

 different ways. In most cases special power exists in soils to 

 remove ammonia, potash, and phosphoric acid from liquid fer- 

 tilizers brought in contact with them ; and less important and 

 more abundant materials pass into the liquid that drains from 

 soils. But this order is reversed if liquid fertilizers act upon such 

 soils as the one used in the experiment before us. Here lime, 

 a cheap and usually abundant ingredient of soils, is actually 



