March 24, 1870. ] 



JOURNAL OP HORTICULTURE AND COTTAGE GARDENER. 



kinds of manures generally placed at the gardener's disposal, 

 and the right method for their preparation and application to 

 the soil. 



Generally speaking, the manures for a garden are obtained 

 from the stable, the piggery, and the cowyard. The organic 

 manures contain chemical constituents which must be carefully 

 guarded. When a heap of manure is in a state of fermentation 

 or decay, it should be covered with some such material as earth 

 or charcoal, to absorb and retain the ammonia which would 

 otherwise be lost ; a covering of earth answers very well, but if 

 fine charcoal can be had it is far preferable, from its greater 

 power of retaining those gases so beneficial to vegetation, and 

 which are the quintescence of a manure heap. Charcoal even 

 alone is a valuable fertiliser, but when it has become charged 

 with ammonia it forms one of the be9t agents for the renova- 

 tion of fruit-tree borders and plantations. If a heap so covered 

 ceases to exhale effluvia, it may safely be concluded that it re- 

 tains within itself all those constituents by which the soil will 

 be benefited. The importance of this principle is far from 

 being so fully recognised as it ought to be. Large quantities 

 of rich manure brought from the farmyard or fattening pound, 

 may frequently be seen heaped on some piece of waste land by 

 the roadside, where it is fully exposed, its po.verful gases con- 

 stantly escaping, and its rich juices, washed out of it by every 

 passing shower, trickling down the road. Thus the richest 

 elements of the heap are wasted and lost. Such sights as this, 

 and they are by no means uueommon, cause one to think that 

 there is some truth in the adage that " a little knowledge is a 

 dangerous thing ; " for this heaping and mixing of manure in 

 order to promote fermentation and decay is sensible and right, 

 because the more manure is decayed when applied to the 

 land the sooner will it become soluble and fit for the food of 

 plants ; but it is in the too frequent exposure to the air for 

 a lengthened period, especially during fermentation (by which 

 process ammonia is developed), and by the washing away of 

 the soluble matter by rain, that error is committed. Yet, 

 although this faulty mode of procedure is bad enough, it 

 becomes far worse if the heap is turned during fermentation, 

 because the gases then generated are partly absorbed and 

 fixed by the cool external layers, and if, after those gases be- 

 come fixed, the outer layers are turnet to the bottom and 

 centre of the heap, the gases would again be set free and the 

 greater part of them lost. 



The degree of decay to which it is desirable that manure 

 should be brought before it is used, depends upon the condition 

 of the soil for which it is in preparation. To a damp heavy 

 loam it is best to apply the manure in as rough a state as 

 possible, as every straw would serve for a time to keep the soil 

 open and admit air ; but in almost every other case, manure in 

 an advanced state of decay is the most valuable. Horse dung, 

 by its stimulating quality, is best adapted to cold clayey soils, 

 while cow dung, from its colder nature, is admirably suited to 

 hot sandy Boils. Pig's dung is considered the most powerful 

 stimulant of the three ; but whatever kind is used, it is of equal 

 importance that it be thoroughly incorporated with the soil, 

 bo that its nourishing constituents may be as equally dis- 

 tributed as possible. — Edward Luckhokst, Egertun Rouse 

 Gardens, Kent. 



THE CHEMISTRY OF MANURES.— No. 2. 



In pursuing the subject of the value of nitrogen in manures, 

 we must bear in mind that all the constituents of a plant have 

 to be assimilated in a state of solution. It would be of just as 

 much use to put an infant into the middle of a yard filled with 

 stacks of Wheat, and to tell it to feed itself, as there was 

 plenty of material in the stacks to make bread of, as to put a 

 plant into the middle of dry straw and expect it to grow. 

 There may be all the materials necessary for the existence of 

 the plant in the straw ; and, moreover, having been already 

 once assimilated, all the inorganic constituents would be in the 

 best possible form to be again up into the tissues of a plant, 

 but the straw will be of no U6e till it be thoroughly decom- 

 posed, and all its particles again rendered soluble. 



The principal constituents of the humus to be found in all 

 our cultivated soils are nearly all of them soluble in ammonia, 

 and this is one of the most valuable of the properties of am- 

 monia. Humus is formed by the decay of animal or vegetable 

 matter ; thus, all farmyard manure before it is capable of being 

 absorbed or assimilated into a plant must first take the form 

 of humus. The composition of this humus is very variable, 

 and has been divided into three groups. The first is the 



humic acid group, which consists of acids formed from carbon 

 and water only. 



Carbon. Hydrogen. Oxygen. 

 Tbas humic acid from the soil 



of a pasture field 40 .. 14 .. 14 



From hard peat 40 .. 15 .. 15 



From soot 40 . . 16 . . 16 



all of which are formed of carbon in combination with a vari- 

 able proportion of water. The second, the ulmic acid group, 

 consists of carbon and water with a variable proportion of 

 excess of hydrogen. The third, the geic acid group, consists of 

 carbon and water with a variable excess of oxygen. 



Now, in all these soils of vegetable or animtil origin, part is 

 soluble in water, part in alkaline solutions, and part, which is 

 called humin or ulmin, is insoluble. Of these three groups 

 which I have alluded to, the geic acid group, which contains an 

 excess of oxygen, is the most soluble in water. The other 

 two groups, the humic and ulmic acid groups, are less so. 



It would take up too much of your space and of your readers' 

 time to enter more fully into the details with regard to the 

 humus of soil, and I would refer those of your readers who 

 wish to study the subject for themselves to the chapter devoted 

 to it in Johnston's " Agricultural Chemistry," pages 69 to 78, 

 &3. I have, however, referred to it because I think ammonia 

 is far more valuable, in the first instance, for the property it 

 possesses of dissolving these different acids, and enabling the 

 sap to take them up, rather than for the nitrogen it contains. 

 It is also, I think, important to note that these different acids, 

 which form part of the vegetable constituents of the soil, are 

 very closely allied to the hydro-carbons found in plants, as 

 gum, sugar, starch, dextrine, etc., all of which, as I pointed out 

 in my last, are formed from carbon with variable proportions 

 of water. Thus humic acid, by the addition of more water, 

 would become starch or gum sugar, just as it may be elabo- 

 rated in the plant. How these different chemical changes take 

 place in the great laboratory of nature is as yet but little 

 known, and is only a matter of conjecture ; but when we find in 

 the earth in which plants grow, different substances which are 

 already formed from decomposed vegetable matter, and are so 

 nearly allied to other substances found in the living plant, it 

 is only fair to argue by analogy that the plant can assimilate 

 these substances more readily than others that are less nearly 

 allied. Now, the acids of these groups — the ulmic, geic, and 

 humic acids — are all of them capable of being dissolved by alka- 

 lies, especially by ammonia, and it is only the geic acid group, 

 which contain an excess of oxygen, which are easily dissolved in 

 water without the aid of some solvent. 



It may be stated as a broad rule that nearly half the weight 

 of plants consists of carbon, which it is very fairly concluded is 

 the most important ingredient in all vegetables ; and though 

 plants have the power of assimilating carbon from the atmo- 

 sphere by means of their leaves, yet a great proportion of the 

 carbon must be elaborated by means of their roots. Liebig 

 lays down a broad rule, that plants take up carbon from the 

 soil in the earlier stages of their growth, but not in the later ; 

 but I look upon this as j ust about as valuable as his broad state- 

 ment that there is no reason whatever to Buppose that plants can 

 assimilate nitrogen from the air. It is too absurd to say that 

 plants can take the carbon which is necessary to their existence 

 from the soil while they are young, but that the power should 

 cease when they get matured, especially, as is well shown by 

 Professor Johnston, plants must absorb much more moisture 

 through their roots during the heat of summer than at any 

 other time, and the leaves in presence of the sun have much 

 more power to elaborate the carbon than at any other time. 

 But not only does the ammonia help to support the carbon by 

 acting as a solvent to these different acids found in humus, 

 but ammonia is also formed by the further decay of vegetable 

 soils. Professor Johnston says, page 76, cap. 3° — " They 

 have all a strong tendency to combine with ammonia. Hence 

 when extracted from the soil they are almost universally found 

 to contain a quantity of this important compound. When 

 prepared in a perfectly pure state, and exposed to the air, they 

 are soon found to contain traces of ammonia. This ammonia 

 is not merely extracted from the air ; it is actually formed 

 either in whole or in part, by the mutual action of these acids 

 and of the constituents of the atmosphere to which they are 

 exposed. The ammonia they are thus the instruments of pro- 

 ducing is one of the agents by which the acids themselves are 

 rendered soluble in water, and thus fitted to become the food 

 of plants." Again, cap. 5° — " The soluble compounds which 

 these acids form with potash, soda, or ammonia, possess the 

 property of dissolving small quantities of the earthy substances 



