Liquid Manure. 21 



into the vegetable organism in a soluble state. I believe that the 

 quantity of water which passes into the plant is amply sufficient 

 to dissolve from the soil a sufficient quantity of the various mineral 

 matters required to meet the wants of cultivated plants. In ac- 

 counting, therefore, for the presence of potash, phosphoric acid, &c., 

 in plants, it cannot be reasonably urged that soluble manuring 

 matters, such as potash, phosphoric acid, &c., in contact with 

 soil, are rendered insoluble, and that therefore plants must take 

 up their food in a solid state. It is true, that the most soluble, 

 and, I may add, the most valuable substances, contained in 

 fertilizing liquids are rendered comparatively insoluble in contact 

 with most soils ; but I feel assured that it is impossible to render 

 them perfectly insoluble. 



All good soils left in contact for a short time with pure rain- 

 water yield a considerable quantity of potash, phosphoric acid, 

 &c., to the water ; and water charged with carbonic acid dissolves 

 a still larger proportion of these and other soil-constituents. 

 Purely sandy soils alter (comparatively) but little the composition 

 of liquid fertilisers which are passed through them ; clay soils, 

 on the other hand, materially alter the chemical constitution of 

 this liquid. If there is truth in the remarks I have made 

 respecting the solubility of mineral food of plants, and the im- 

 probability of plants taking up food in a solid form, we may 

 expect that no soil, however stiff it may be, will completely 

 remove all the ammonia, potash, phosphoric acid, &c., contained 

 in dilute fertilizing liquids. On the other hand, if plants can 

 take up solid food in some mysterious unexplained manner, it 

 would not be surprising that clay soils rendered insoluble the 

 whole of the ammonia, potash, &c., contained in a fertilizing 

 liquid : for, supposing this to be the case, the plant might still 

 grow luxuriantly. The changes which manuring liquids undergo 

 in contact with soil, it will be perceived, have a much wider 

 application than may appear at first sight ; they are, indeed, 

 intimately connected with the theory of vegetable nutrition. I 

 am happy, therefore, to be able to report a fifth experiment, 

 which is of peculiar interest in this respect. The experiment 

 was made with a soil from Tiptree Hall, kindly sent to me by 

 Mr. Mechi. This soil, and the subsoil on which it rests, 

 yielded, on mechanical analysis : 



Subsoil. Surface-soU. 



Moisture 9-46 3*91 



Organic matter and water of combination .. 4*87 4'80 



Sand 9-26 10'97 



Lime 1-12 2-19 



Clay 75-29 78*13 



100-00 100-00 



c 2 



