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of the Andes wheat fields, which had yielded excellent crops annually for more than two centuries. Maize may likewise be continually reproduced upon the same ground without inconvenience; this fact is well known in the south of Europe; and the greater portion of the coast of Peru has produced nothing else, from a date long anterior to the discovery of America. Further, potatoes may come again and again upon the same soil; they are incessantly cultivated_at Santa-Fé and Quito, and nowhere are they of better quality. Indigo and sugar-cane may be brought under the same category. In Europe the Jerusalem artichoke produces constantly in the same place.* It must be conceded, that if all these plants excrete from their roots, their excretions are not of such a nature as to interfere with the progress of vegetation of the species producing them.

But the capital objection to the hypothesis of De Candolle is this, that it would be very remarkable indeed did any soluble organic matter, like such secretions, not putrefy when lying in the ground. In a word, it is difficult to understand how it should resist for years, as is pretended, the decomposing influence of heat and moisture together.

That there is no absolute necessity for alternation of crops when dung and labor can be readily procured, is undeniable. Nevertheless, there are certain plants which cannot be reproduced upon the same soil advantageously except at intervals more or less remote. The cause of this exigence on the part of certain vegetables is still obscure, and the hypotheses propounded for clearing it up far from satisfactory.

One of the marked advantages of alternate cultures, is the periodic cultivation of plants which improve the soil. In this way a sort of compensation is made for exhaustion. The main thing to be secured in rotation of crops is such a system as shall enable the husbandman to obtain the greatest amount of vegetable produce with the least manure, and in the shortest possible time. This system can be alone realized by employing in the course of rotation those plants which draw largely upon the atmosphere.

The best plan of rotation in theory, is that in which the quantity of organic matter obtained most exceeds the quantity of organic matter introduced into the soil in the shape of manure. This does not hold quite in practice. It is less the surplus amount of organic matter over that contained in the manure, than the value of this same matter which concerns the agriculturist. The excess required, and the form in which it should be produced, must vary widely according to locality, commercial demand, and the habits of people, considerations wholly apart from theoretical provisions. One point

* To this list might be added, according to the recent researches of M. Braconnot, the bay-rose with double flowers, and Papaver somniferum. That distinguished chemist terminates his memoir as follows: "My experiments are unfavorable, as may be perceived, to the theory of rotation of crops based on the excretions of the roots. These excretions if really occurring in the formal state are so obscure and little known as to lead to the inference that the general system of rotations must be referred to some other source. (Recherches sur l'influence des plantes sur le sol, Annales de

Chimie t lxxii. p. 27.)

in theory that should agree with practice is this, that in no case is it possible to export more organic matter, and particularly more azotized organic matter, than the excess of the same matter contained in the manure which is consumed in the course of the rotation. By acting upon another presumption the productiveness of the soil would be infallibly lessened.

This irrefragable condition as to the term of exportation from a farm suggests some critical remarks upon sundry notions lately promulgated. The manufacture of beet-root sugar is an instance. European agriculture may probably derive certain advantages from this modern branch of industry, although these have been much overrated by certain speculators, who contend that sugar may thus be obtained through rotation of crops without lessening the other produce of the domain; so that the sugar constitutes an additional source of income. This seems to me erroneous.

To

If an estate yields annually 100 tons of beet-root for the support of cattle, their number must be diminished if the root is to be used for making sugar. The organic matter of the sugar extracted therefrom, is just so much nourishment withheld from the cattle. assert the contrary would be equivalent to saying that potatoes grown upon a couple of acres of land, and submitted to the process of distillation before being employed as fodder, would feed as many animals as if eaten directly assuredly, the organic principles of the potato converted into alcohol are lost as regards nutrition.

This does not imply that the manufacture of indigenous sugar, and of potato spirit, is less productive than breeding and fattening cattle. My sole object is to show that only a limited quantity of organic matter can be advantageously exported from an agricultural establishment. It must depend upon local and commercial circumstances whether this is to be exported in the form of sugar, corn, spirit, or butcher-meat.

The above statement is in apparent contradiction with generally received notions. Many persons believe that the manufacture of sugar, instead of injuring, is favorable to the breeding of cattle. It appears, from a Parliamentary return on this subject, in 1836, that in certain estates where sugar was made, the number of animals was increased; the numerical results are no doubt exact, but this augmentation in cattle is rather to be ascribed to an improved mode of farming than to the manufacture of sugar. In establishments where the triennial rotation with fallow was pursued, a rotation of four or five years with clover and weed-destroying plants has been introduced; so that it is by no means to be wondered at, that independently of beet-root, there should have been a considerable increase in other things. The introduction of this root, where it was not formerly grown, is of itself an important melioration. But in highly cultivated countries, where the most productive rotations have been long followed, the extraction of sugar would not effect such advanIf at tageous changes as those announced in the above return. Bechelbronn a time should ever come, and at present it seems far distant, when it would be deemed expedient to make sugar from the

beet there grown it would certainly be requisite to diminish the number of cattle, or else to annex more meadow land. It is only indirectly, therefo: e, that the manufacture of home-sugar can promote the breeding of cattle, and so prove serviceable to agriculture. From the definition given by me of the most advantageous course of crops, theoretically considered, it may be inferred how closely the study of rotations is connected with that of the exhaustion of the soil. Hence, to discuss the value of divers rotations, we must, in consonance with theory, compare the quantity of organic matter in a sequence of crops, with that in the manure expended upon them.

From a well-managed farm, where for a series of years an invariable system of culture has been steadily pursued, we must look for data. This I have done, as regards Bechelbronn, determining by analysis the composition of the manures and crops, and also of the more ordinary kinds of fodder or food. For a long time, a five years' rotation has been there adopted in the following order:

1st year.-Potatoes or beet-root manured.

2d year. Wheat sown the autumn of the first year; clover interposed in the spring. 3d year. Trefoil (clover) two crops; the third crop ploughed in or smothered. 4th year.-Wheat on the clover-break, turnips after the wheat.

5th year.-Oats.

The crop of oats which ends the rotation is generally scanty. The soil is then brought back to the point of fertility which it had before being dunged; and it is known by experience that it will not now yield a crop of any value.

I now proceed to detail the analyses of the different substances which enter into the rotation, indicating at the same time the average produce per acre.

POTATOES.

In the rather strong soil of Bechelbronn one acre produces upon an average about 105 cwts. of potatoes. This is below the ordinary rate of Alsace, where the crop amounts to from 155 to 165 cwts. per acre. The leaves and stems are left upon the ground.

A potato was cut in two, in order to subject it to analysis with a proportional part of the peel. The half weighed 335.2 grs. Stovedried and reduced to flour, it weighed 289.3 grs. By absolute desiccation in vacuo, at a temperature of 230° F. it was found that one of moist tuber became 0.241; 15.4 grs. left of ash 0.039.

The average quantity of azote is 1.2. In 1836, I found 1.8 of azote. This notable difference, perhaps, depends on the analysis not having been made immediately after the harvest; or it may be partly due to meteorological influences. To convince myself that it did not depend upon any error of analysis, I examined anew the potato of 1836, preserved in the farinaceous state: it yielded 1.8 of azote. I shall, therefore, reckon the azote at 1.5:

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WHEAT.

I analyzed the grain gathered in 1837: one of wheat, dried in vacuo at 230° F. was reduced to 0.885; one of dry wheat left of ash 0.0243:

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The mean produce in wheat at Bechelbronn varies from 20 to 22 bushels per acre; this variation depends on the drill crop which commences the rotation. After potatoes the average crop is 19 bushels; after beet-root, 17 bushels; on clover-breaks it is 24 bushels. The average weight of the grain is 63 lbs. per bushel.

WHEAT-STRAW.

I estimate the proportion of the produce in grain to that in straw, as 44 to 100.

One of straw completely dried in vacuo at 230° F. becomes 0.740; one of dry straw leaves 0.0697 of ash :

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Clover delights in clayey soils; it thrives generally in good wheat lands; in light and sandy ground it gets bare and frosted. During its growth, it always requires the shelter of some other plant. For this reason, in spring, it is generally sown among wheat, which is put in the preceding autumn, or barley sown the same spring. We generally give from 11 to 14 lbs. of seed per acre. Clover is mowed the second year, as it is coming into flower; but when it is not to be consumed as green fodder, the mowing may take place before the flowering; this is required from the difficulty of making it into hay. In fact, in the process of drying clover, there is great risk of losing part both of the leaves and flower; besides, the drying always requires a considerable time, during which the clover runs the chance of being damaged by rain, and clover hay-making is almost impracticable in wet weather. Schwertz proposed to dry the clover on a sort of parrot-perches stuck into the ground. These supports are but eight feet high, and capable of bearing a load of 2 cwt. of green fodder, mowed twenty-four hours, and already withered. This method, as I have seen it practised in the Duchy of Baden, answers well, but there is considerable cost for manual labor, and in the first instance for perches. Schwertz reckons that 2 cwts. of green clover

yield 48 lbs. of hay.

with the age of the

The relation of green to dry fodder varies plant, and the meteorological circumstances under which it has grown. Subjoined is the result of some experiments which I performed on the making of clover hay:

1 ton of clover in flower, 2d year (1841) afforded in hay 7 cwts. 1 ton of clover

1st year (1842)

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4 cwts. 2 qrs. 24 lbs.

The average produce of this fodder reduced to hay at Bechelbronn is 41 cwts. 3 qrs. per acre.

One of clover hay, after complete desiccation, weighed 0.790; one of dry hay left 0.078 of ash :

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When turnips are cultivated as a second crop, as after rye or wheat, the produce is very uncertain. Attempts are occasionally made to raise them after wheat which has followed clover.

When cultivated on fresh manured soil, the produce is considerable; in some places it amounts to from 28 to 33 tons per acre; but as a second crop, we only obtain upon an average 71 tons per acre. This crop is only counted as a half-crop in the general produce of the rotation.

Turnip the most watery root I have examined. A slice weighing 2 oz. 17 dwts. dried in the stove, was reduced to 4 dwts. After thorough desiccation, one of turnip weighed 0.075; consequently the root contains 92.5 per cent. of water; one of dried turnip incinerated, left 0.0758 of ash :

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As this grain closes the rotation, the produce is not great. The average crop is 37 bushels per acre, at the weight of 33 lbs. per bushel;* one of oats completely dried weighs 0.792; one of dried oats leaves 0.0398 of ash :

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* This is but a light weight for a bushel of oats.-ENG. ED.

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