ADDITION OF GUANO TO FAKM-YAKD MANURE. 



That guano should not produce much effect in very 

 dry weather needs no explanation, because, without 

 water, no substance will act in the ground ; that it 

 should, however, equally fail in very wet weather, is, 

 undoubtedly, owing in part to the fact that the oxalic 

 acid is washed out, as an ammoniacal salt, by the rain 

 water, and that there is, accordingly, a corresponding 

 quantity of phosphoric acid not made soluble. By the 

 above simple and cheap means the injurious influence 

 of wet weather upon guano may be completely guarded 

 against, inasmuch as the water and sulphuric acid en- 

 sure the conversion into a soluble form of the whole of 

 the phosphoric acid, which could have been brought in 

 to that condition by the oxalic acid. 



The rapidity with which a nutritive substance em- 

 ployed in the shape of manure produces an effect, de- 

 pends essentially upon the speed with which it spreads 

 through the soil, and this, again, upon its solubility ; 

 hence it is easy to understand why guano surpasses, in 

 these respects, many other manures. 



As regards certainty of action, guano will not bear 

 comparison with farm-yard manure, which, from its 

 nature, is effective in all cases ; for farm-yard manure 

 restores to the land all the soil constituents of the pre- 

 ceding rotations, though not in the same proportions, 

 whereas guano restores only some of them, and cannot, 

 therefore, replace farm-yard manure. As guano, how- 

 ever, contains, with the exception of a certain quantity 

 of potash, the chief constituents (phosphoric acid and 

 ammonia). of the exported corn and flesh, the addition 

 of a certain proportion of guano to farm-yard manure 

 may serve to restore the proper composition of the lat- 

 ter, and, with it, also that of the soil. 



Let us suppose, for the purpose of illustration, that 

 a hectare of land has been manured with 800 cwt. of 

 farm-yard manure, containing, according to Voelker's 

 analysis, 272 kilogrammes of phosphate, and that the 

 field has, at the end of the rotation, returned the same 

 quantity of farm-yard manure of the same composition, 

 and has lost by the corn and the animal produce export- 

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