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they are also of value by facilitating the decompositionof vegetable substances employed as manure,
400. As perhaps the most useful part of these kindsof manure is the volatile substances formed during theirdecay, great care should be taken to suffer as little aspossible to escape and be lost. It is probable that thebest method of preserving the greater part of thesematters is to dissolve it in water. The employment ofliquid manure is gradually coming more and more intouse, and the prejudices against its application are vanish-ing, as the beneficial results produced by its use becomeknown.
401. The greatest attention should be paid to themodes of collecting, preserving, and economising animalmanure. There can be no doubt that a very largequantity of manure is constantly wasted under the oldsystems of using it, and the least consideration willconvince any one of this.
402. The food of plants consists principally of certainvolatile or gaseous substances, produced, amongst otherways, by the decomposition of organic matter; we addorganic matters to the soil, to supply plants with morefood than they could otherwise obtain. If, then, previousto using these substances as manure, they are exposedfor some time to the air, sun, and rain, a considerableportion of the volatile products of decay will be lost;and this is constantly done.
403. Manure should be carefully collected — noneshould be neglected or suffered to go to waste ; it should
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