193 



ROTATION OF CROPS. 



ROTATION OF CROPS. 



194 



round A B, and its equal and contrary round F, produce nothing but 

 a motion of translation, while the remaining rotation about E F, corn- 



Fig. 3. 



pounded by the first rule with that about c D, gives what would be 

 an axis of repose, if it were not for that translation. The whole result 

 then irt, that the system begins to move about an axis, which axis 

 begins to undergo a translation in space. 



For higher theoretical investigations in this subject, the reader is 

 referred to the writings of M. Poinaot. The best practical view will 

 be derived from experiments with the GVBOSCOPE. See also an 

 article on the Gyroscope by Mr. John Bridge in the ' Philosophical 

 Magazine ' fur November, 1857. 



KI iTATION OF CROPS. It has been observed in a former article 

 [ARABLE LAND] that a repetition of the same crops in succession has a 

 peculiar effect on the soil, so that if grain of the same nature be sown 

 year after year in the same ground, it will not produce the same 

 return of the seed, even when abundantly manured. The reason of 

 this is not satisfactorily explained, but the experiments which have 

 been made bj men of science lead us to conclude that the real cause 

 will be gradually discovered; and considerable advance* have been 

 made towards a rational solution of the question. It has been observed 

 that it is the formation of the seed which principally causes the 

 deterioration of the soil ; for if the crop be fed off in a green state, or 

 mown Iwfore the seed is formed, the same may be safely repeated, and 

 no diminution of the plants is apparent. Thus grasses in a meadow 

 which are mown before the blossom is faded or the seed formed, will 

 .-]>rini< up again vigorously; but if the seed be allowed to ripen, the 

 roots die away, and the best grasses gradually disappear. It is thus 

 that when a meadow is mown year after year for hay, and the earliest 

 gnus oe are allowed to ripen their seed, the crop will be later and later, 

 and all the earliest grasses will disappear. Irrigation prevents this, 

 and seems to restore to the land whatever the RiimiiiH require for their 

 continuance. Feeding off the meadows does the same ; and this leads 

 that water restores the power of production ; and 

 tli if. the grasses not being permitted to run to seed, the deteriorating 

 effect is not produced. 



If it had been a mere exhaustion of the nutritious particles in the 

 noil which caused the deterioration of the subsequent crops, some kind 

 of manure might restore the fertility ; but this is not the case. How- 

 ever judiciously the land may be manured, it is not practicable to 

 raise a crop -of wheat or clover, or of many other plants, on a soil 

 which has shown that, as the farmers say, it is tired of that crop ; but 

 clover grows well after wheat, and wheat after clover, so that the same 

 fleet is not produced in the soil by these two crops. A plant which 

 has fibrous roots, and throws up a seed-stem with few leaves, thrives 

 bat after one which has a fleshy root and many succulent leaves on a 



i'i.iii< i;iii_- - i.i. TliM- !.--.'- .iif I MSI tiiri.-- if-- r ': : H -1 '.!. 

 barley and oats after turnips, carrots, or potatoes. Independently of 

 the manure which may be put into the ground, the crops will be better 

 where the proper succession is attended to, than where plants of a 

 .-iinilar kind are nude to follow each other. 



In all countries where peculiar attention has been paid to agriculture, 

 tin- most advantageous succession of crops is generally known ; and if 

 any deviation takes place, it is as an exception to the rule, and is not 

 looked upon as a model for imitation, but rather as an experiment of a 

 doubtful result Certain general principles are commonly admitted as 

 fully established ; the chief of these is, that a plant with a naked stem 

 and farinaceous seed should follow one with a branching stem and a 

 fleshy root, which has been taken from the ground by mowing or 

 .- before the seed was ripe; or if all these conditions cannot IT 

 obtained, that some of them at least should be complied with. Wheat 

 sown after clover, which is allowed to be the best succession on light 

 soils, fulfill all the conditions : when it is sown after beans, the con- 

 dition of the preceding crop not ripening its seed is given up; and 

 consequently this succession is inferior to the other, but it is admirably 

 effective nevertheless on all heavy soils. Potatoes, at first sight, appear 

 to fulfil all the necessary conditions ; but although they do not often 

 ripen the seed above ground, in the formation of the tubers the soil is 

 notoriously deteriorated. 



In order to find the crops which may advantageously succeed each 

 other in rotation, many circumstances must be taken into considera- 

 tion. First of all the quality of the soil, and its fitness for particular 

 crops ; next the wants of the farmer and his family, and the mainte- 

 nance of the stock r<i|iiir<il to produce a sufficient supply of manure. 

 It is unri-.won.ible to expect poor light land to produce wheat and 

 beans, although by high cultivation these crops may be forced. Rye, 

 oats, and roots may give the fanner a better profit, by being raised at 



ARTS AXD SCI. DIV. VOL. TIL 



a less expense than more valuable crops, which must be forced with 

 manure, and at best are precarious in soils not adapted to their growth. 

 In moderate loams wheat may recur every fourth or fifth year, 

 whereas in very rich compact loams it may recur every third, and even 

 every alternate year. Clover and many artificial grasses do not succeed 

 well if they recur oftener than every sixth year, or with even a longer 

 interval. Rape, flax, and potatoes require a still more distant recur- 

 rence on the same ground. All these considerations lead the farmer 

 to the selection of the most advantageous rotation for the soil of his 

 farm ; and where the land in a considerable district is nearly of an 

 uniform quality experience soon establishes a course which no one 

 finds it prudent to deviate from. It happens frequently however that 

 a great variety of soils, very different in their nature and fertility, are 

 intermixed ; and then, unless the farmer can apply the true principles 

 of rotations, he may greatly err by following the course, which may be 

 very judicious for the prevailing soil of the district, but not at all 

 suited to some of his fields. Hence a knowledge of the crops suited to 

 any jiarticular soil, and the order in which these crops should succeed 

 each other, is indispensable to the advantageous cultivation of a farm. 



That which forms the food of man is always the principal object in 

 the cultivation ; and, excepting rice, which only grows in warm 

 climates, there is no food more universally used than that which is 

 made from wheat. Rye, barley, oats, and pulse are only substitutes 

 where wheat cannot be raised in sufficient quantities. Next to grain 

 comes meat, chiefly beef, mutton, and pork, of which the consumption 

 increases with the wealth of a nation and the advance of its agricul- 

 ture. Wheat and fat cattle are therefore primary objects with every 

 good farmer ; and he who can raise most wheat and fatten most oxen 

 or sheep or pigs will realise the greatest profit. 



Many circumstances may indicate a deviation from the course which, 

 as a general rule, is most advantageous. The facility of purchasing 

 manure from neighbouring towns may allow of more frequent crops of 

 corn, and of nutritious roots which require much manure, such as 

 potatoes, and which give no return to the land in the shape of dung. 

 But we must lay down rules for those who are to rely on their own 

 resources to recruit the land with manure, so that it may give the 

 greatest produce without diminishing in fertility ; and this can only be 

 done by a judicious feeding of livestock. 



The simple rotation of wheat and beans alternately would be by far 

 the most profitable in rich clay soil, as both these crops always obtain 

 a good price in the market; but if a whole farm were so cropped, 

 nearly all the manure must be purchased ; for, after a few crops, the 

 wheat-straw and bean-halm would not produce half the manure re- 

 quired for the land. Hay and oats must be purchased for the horses 

 required for the tillage, which might not be procured so readily or so 

 cheap as they may be raised on the farm. On very light sands wheat 

 or beans cannot be raised, except by a very expensive mode of culti- 

 vation ; but rye, oats, peas, buckwheat, and roots for cattle must be 

 substituted. On chalky loams the principal crops are barley and 

 artificial grasses for sheep. In short, no particular rotation can be 

 prescribed without a complete knowledge of the soil, the locality, and 

 every circumstance connected with any particular farm. As the most 

 universal rule, it may be laid down that every alternate crop should 

 be consumed by niml on the farm, and that, as much as possible, 

 the plants which succeed each other should be of different natural 

 botanic families. Experience has generally shown the time that should 

 be allowed to intervene between the recurrence of the same kind of 

 crop, and we have only to form our plans accordingly. 



Of the old triennial course (fallow, wheat, barley or oats) it mn.-t lie 

 observed that the two corn-crops so rapidly deteriorate the soil, that a 

 complete year of fallow is required to purify it, and a good manuring 

 to keep the land in heart, and that all the industry of the farmer 

 cannot keep up the fertility of the land without extraneous help, 

 either from the manure made in towns, or in the farm-yard by cattle 

 bred and kept in commons or pasture-grounds. This system, which 

 prevailed so long, cannot be called a rotation ; and no real improve- 

 ment was introduced into agriculture until the notion of its perfection 

 was exploded, and tenants were permitted to deviate from it. The 

 rotations adopted in the place of this old system necessarily partook at 

 first of its main defects. Green crops were introduced of necessity to 

 supply the loss of the commons and pastures, which, as the population 

 increased, were gradually cultivated as arable land : but the two white 

 crops remained in succession, and even now, such is the force of habit 

 and early impression, that one of the most difficult points to be gained 

 with practical farmers, accustomed to the old rotations, is to make 

 them have patience when their land is in a good state, and to prevent 

 then- sowing a white crop, which is immediately profitable, instead 

 of a green crop, which will keep the land in heart and improve it for 

 future crops, but which does not figure in the account of sales. Yet 

 it can be clearly shown, that in most cases the second corn crop is 

 dearly purchased by the expense required to restore the land to the 

 state in which it was when the seed was sown a second time : manure 

 alone will not do this ; fallowing and repeated ploughing can alone 

 effect it : and whether you plough several times before a crop, or are 

 forced to do so after it, there is no difference in the expense of labour, 

 although there may be much in the value of the subsequent crops. 



The Norfolk course (turnips, barley, clover, wheat), which is so well 

 known and deservedly in repute for light sands, has only one defect, 



