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Their agricultural character, as described by the farmer, are pretty much alike; the three soils are all of high productive power; but their crops are liable to drought and frost, in circumstances under which the crops of other fields in the immediate vicinity do not suffer.
To correct the evil, the farmers applied lime, and had recourse to hurdling the sheep on the fields during the nights, but without attaining the object they had in view.
The cause of the failure, both of crops and of remedies, is obvious.
The examination of the physical character of the soils shows that their mean capacity for moisture is + 3; their mean absorption of solar says + 16*3; and their terrestrial radiation or emission 8'8; and, consequently, that the one is to the other in the proportion of 1*9 : 1.
Now, in the conclusions which have been drawn from the comparison of fertile and sterile soils, it has been said, that unless the capacity for moisture is + 14, and the absorption to emission is as 5'76 : 1, the production of crops will be precarious.
Hence, before the actual failure of the crop showed the inaptitude of the soil for it, both the frost and drought could have been predicated from the mere examination of the soil; and thus labour, time, and expense might have been saved.
But the examination which proves the defects of the soil, points out also proper remedies to correct them. Experiments which were adverted to in the section on climatology, lead to the belief that the presence in a soil of vegetable matter in certain quantities increases its absorption of solar heat; lessens its emission, and heightens its capacity for moisture; and that 15 per cent, of this matter is highly beneficial to a soil, and 5 per cent, highly injurious.
Now, in the instance before us, the chemical analysis of the three soils shows that, on an average, they possess but 4*5 per cent, of vegetable matter; and hence it is evident that the remedy lies in the augmentation of the vegetable part, by the sowing and ploughing in of the grasses.
But the advantage derived from the study of the physical character of soils intended for cultivation, is not limited to the mere question of frost and drought; that study can indicate to the farmer which soil, out of many productive ones, is the fittest or the best calculated for early crops. For example, in Table I. of the fertile soils, we see that the relation between absorption and emission of heat in the soil No. 3, is equal to that of No. 26; in both cases, the one property to the other is as 3*5 : 1; however, notwithstanding this, soil No. 26 will accelerate the vegetation, as, by virtue of its colour, it absorbs 21° of heat, in circumstances under which soil No. 3 absorbs but 7°.
The application of the chemical knowledge of the soil takes in a still wider range.
Soils No. 16 and 17, in the second table, are represented by Mr. Kennode as being unproductive and subject to frost. Now, the chemical analysis points out the cause of this sterility, in the presence of salts of the peroxide of iron, and in the absence of vegetable matter; and in disclosing the defect, it shows the remedy also, in the application of lime; by the addition of which, the subsulphate of the sequinoxide of iron being converted into peroxide, and the slacked lime into sulphate or gypsum, the soil will be raised from the lowest to the highest degree of productiveness. Sowing grasses, and ploughing them in, will complete the improvement.
But if horse-manure is at hand, it will supply both the exigencies most effectually, as by the analysis of horse-dung, we find that it contains 60 per cent, of
magnesia and lime, both valuable ingredients, per se, and the more so in the case of the soil in question, on account of the presence of the salts of iron.
Thus, it may be seen, how a knowledge of the chemical and physical characters of soils will lead to the right application of manures, and to the process of restoring to the soil what is abstracted from it by cultivation, with a certainty as to the result.
The manures proper for such restitution, or amelioration and correction of the defects of soils, are innumerable. The one which is within the reach of the Australian farmer, and is the cheapest, answering even in an extreme case, is that derived from the farm-yard. "The solid and liquid excrements of an animal are of the highest value as manure for those plants which furnished food to the animal.
"The dung of pigs fed upon peas and potatoes is in the highest degree adapted as a manure for fields growing peas and potatoes. AVe feed a cow upon hay and turnips, and we obtain a manure containing all the mineral constituents of grass and turnips: this manure ought to be preferred, as being more suitable for turnips than that procured from any other source. The dung of pigeons contains the mineral ingredients of corn; that of rabbits the constituents of culinary vegetables; the liquid and solid excrements of man contain, in very great quantity, the mineral substances of all seeds."
But this most valuable farm-yard manure cannot be obtained of proper quality, and in sufficient quantity, to meet the exigencies of an Australian farm, except by stall feeding, or stabling the milch cows*, which requires the increasing of the pasture or green crops, which, again, cannot be done without the introduction of irrigation.
* "The agricultural societies, the numbers of which are, in the present day, so greatly multiplied, would render a real service to agriculture, if they encouraged, by every means at their disposal, the economy of manures; if they established premiums for the farmers
who should show that they kept and managed their dunghills in the most approved and rational manner.
"The most proper spot on a farm for the manures to be deposited, is the vicinity of the stables and cow-houses. The localities may vary to infinity, but in every farm they should be such as to allow of the following conditions being realised.
"1st. That the liquid matter in the dunghill should not drain away from it. 2dly. That this matter should be gathered in a common reservoir formed in the ground, so as to be thrown back, in times of drought, on the solid mass. 3dly. That all watercourses should be prevented from emptying themselves in the depot, or any other water, except the rain that falls on the surface. 4thly. That the area of the depot be sufficiently large to obviate the necessity of heaping the dung too high. It is a great advantage, if the spot on which the manure is placed can be rendered slightly concave, and the reservoir fixed in the lowest part: also, if the soil be a stiff, impermeable clay: otherwise it will be necessaiy to lay a good pavement. The liquid matter from the dunghill, which collects in the reservoir, should be thrown back on the heap when the surface becomes too dry, by means of a pump. To aid this operation, Shaverty recommends moveable troughs or conduits placed on supporters, varying in length, and so adjusted one to the other as to carry the liquid to all parts.
"The mouth of the reservoir, which is necessarily under the manure, must be closed by a very strong wooden grating, the bars of which must lie sufficiently near together to prevent solid matter, straw, &c. from passing. Another most important and essential arrangement is, the having the slope or fall so managed, that the urine from the stables, &c, and the slops from the house, find their way, naturally, to the dunghill. The litter in the stables, however abundant it may be, never absorbs the whole of the urine, especially at the time when the cattle is fed on green food; and the fault that would be committed by neglecting to direct it to the dungyard would be unpardonable. The litter impregnated with excrement, and saturated with urine, must be brought in a barrow without sides, but the dragging it on a fork must not be tolerated, unless the distance be extremely short: if this distance be considerable, a very sensible loss would be thus incurred.
"The various composts should not be thrown carelessly on the heap, but duly spread and divided. An uneven surface occasions inequalities in the mass below, which, in course of time, produce mouldiness. The dunghill must also be properly and compactly piled, in order to check that rapid fermentation which is always prejudicial, and which is apt to take place when the manure is too loosely laid together. It requires special care to watch that the mass preserves, during hot weather, a certain degree of humidity on its surface, which is maintained by frequent use of the pump. At Uechelbrunnen, the manure is laid toge
Irrigation then becomes the first measure with which the agricultural improvements of Australasia must begin.
ther sufficiently closely for a loaded cart, drawn by six horses, to pass over it without much difficulty. The height of the collected mass is not altogether unimportant. Besides the convenience of loading, which ought not to be forgotten, too great a thickness might be injurious, as causing too high an elevation of the temperature; and if, owing to circumstances, a mass of too great a thickness were left undisturbed for a long period, the decomposition might become rapid enough to occasion very serious loss. Experience has proved that the height of the dunghill ought to range between three and six feet. This height lessens gradually on each side until the extremities of the mass form a level with the soil; for it is the custom to preserve a convenient slope for the carts. In Alsace, the loading is performed on the dunghill itself.
"When circumstances, such as the small size of the farm, &c, do not permit the construction of a reservoir, and when the soil is porous, and the farmer has no means of paving, there is great risk of losing the juices of the dung heap. The plan then to be pursued, is to cover the surface of the hollow, in which the dung is deposited, with a layer of earth, sand, peat, or marl; in short, with any dry porous substance capable of absorbing the moisture. This is a practice often advan. tageously resorted to in Alsace.
"When the litter, impregnated with animal excrement, is accumulated in sufficient quantity, fermentation soon shows itself; the temperature rises, and abundance of gas is speedily disengaged. Among the volatile components of this decomposition, is carbonate of ammonia, which it is important to retain. This is done by keeping the mass in a suitable state of humidity, and by favouring, as much as possible, the access of atmospheric air. The daily addition of fresh litter from the stables, &c. powerfully contributes to prevent the escape of the volatile principles it is so important to preserve. If laid on judiciously, it becomes a check to this evaporation, forming a cover which acts as a condenser, at the same time that it preserves the lower layers from a too immediate contact of oxygen. So long as the dunghill is managed in this way, the fermentation is kept from spreading to the inferior layers of the mass.
"Thaer found that the stratum of air which is immediately above the surface of a heap of manure, subject to a moderate fermentation, does not contain much more carbonic acid than that which is further distant. The slow decomposition which this proves, and which is advantageous, is not easily maintained, except in masses sufficiently compressed, and in which the litter has been spread as equally as possible. One important point is to remove the dung before the upper portion, recently added, begins to enter into the state of decomposition; otherwise the entire mass is drawn into full fermentation, and the volatile matter, being no longer arrested by the upper layer, escapes into the air. A means of preventing this loss, when (which is rarely the case) there is a reason for wishing the fermentation to spread itself at once through the