8 Liquid Manure. 



experiment with the same results, and find in all instances in 

 which I operated with liquid manure upon soils rich in oxide of 

 iron and organic matters, that oxide of iron is dissolved. In 

 other cases no oxide of iron passed into the liquid manure. 

 May not the oxide of iron, dissolved in considerable quantities 

 from some soils through the agency of liquid manure, be injurious 

 to vegetation, and partly account for the failure that is expe- 

 rienced with liquid manure on some soils ? 



5. Lime, it will be noticed, was rendered soluble by the liquid 

 manure left in contact with soil. An imperial gallon contained 

 nearly 11 grains more after than before filtration. Most of the 

 lime occurred originally in the manure as bi-carbonate, and some 

 only as sulphate. In the same states of combination, no doubt, 

 the greater part of the lime occurs also in the filtered liquid. 



Combining the sulphuric acid with lime, and the rest of the 

 lime with carbonic acid, we have in this liquid manure, before 

 and after filtration through soil : 



Before After 



Filtration. Filtration. 



Sulphate of lime 6-69 4'89 



Bi-carbonate of lime 22'45 50'24 



Whilst thus the proportion of sulphate of lime in the filtered 

 liquid is but little diminished, that of bi-carbonate of lime is 

 very much greater than in the original liquid manure. 



6. The small proportion of potash left in the manure after 

 contact with soil is particularly interesting, inasmuch as it shows 

 that the soil not only possessed the power of absorbing ammonia, 

 but also potash a constituent which in an agricultural point of 

 view is of the greatest importance. It appears that potash is 

 retained by the soil even with greater avidity than ammonia. 



Besides the potash, which for the greater part exists in the 

 liquid before and after filtration as carbonate of potash, the soil 

 absorbed the whole of the chloride of potassium. 2*74 of 

 chloride of potassium correspond to 1'73 of potash, which 

 quantity added to the 16*92 grains of potash, present chiefly as 

 carbonate of potash, gives 18 '65 grains of potash in the gallon, 

 or, expressed as carbonate of potash, 27'25 grains. After contact 

 with soil, the gallon contained 3'40 grains of potash, or 4'99 of 

 carbonate of potash. 



15-25 grains of potash, or 22'76 of carbonate of potash, were 

 thus absorbed by 20,000 grains of soil. 



1000 grains absorbed '763 of potash, or 1-138 of carbonate of 

 potash. 



7. In a much minor degree than potash the soil absorbed 

 chloride of sodium. By far the larger proportion of common salt 

 remained in the liquid. This result agrees perfectly with previous 

 observations, and with all the experiments noticed in this paper. 



