FARMERS' REGISTER— ROTATION OF CROPS. 



11 



leaves and compact bark, since a greater portion 

 of the nutriment of the former is derived from the 

 atmospliere. 



It is further obvious that, as vegetables Avith a 

 system of large leaves, draw much more of their 

 food from the atmospliere than from the soil, if 

 they be returned wholly, or in greater part, to the 

 soil, it will receive more of the principles of fer- 

 tility than it has lost ; and that their tendency 

 must be eminently enriching. On the contrary, 

 as plants with a system of narrow leaves receive 

 their nourishment principally from the soil, if the 

 greater part of their product be removed from it, 

 that which is restored to tlie earth is less than what 

 has been taken from it, and their effect will be ex- 

 hausting. 



The different proportions, iuAvhich different ve- 

 getables derived their nourishment from the soil 

 and atmospliere, is considerably influenced by tlie 

 changes which tliey undergo in their organization 

 during their growth. Before tlie period of flow- 

 ering, a greater proportion of their nutriment is 

 derived from the atmosphere. But the reverse 

 takes place during the maturing of the seed. The 

 proportion of food derived from the soil while the 

 seeds are ripening, also depend much upon the 

 peculiar character, and the chi^nges which tlie 

 other parts of the plant undergo at that time. The 

 more oleaginous and farinaceous the seeds, and the 

 greater their weight in comparison with the other 

 parts of the vegetable, the greater is the proportion 

 of nutritive principles furnished by the soil. This 

 is still more increased when the leaves, bark, and 

 other spongy parts of the plant, become dried up 

 about the period of flowering, and the nourish- 

 ment requisite to the perfecting of the seeds, is ne- 

 cessarily derived entirely through the roots, from 

 the soil. 



From the review of these principles of vegeta- 

 ble physiology, we arrive at the practical infer- 

 ence, that by the cultivation of crops with systems 

 of large leaves, the soil is less exhausted, than if 

 it be made to produce those with narrow leaves : 

 that if the broad-leaved plants are cut before the 

 period of flowering, they are still less exhausting, 

 than if allowed to mature their seeds : and that ii 

 the product of their vegetation be returned whol- 

 ly, or in greater part to the soil, they become em- 

 inently fertilizing. Hence they have been called 

 ameliorating crojjs. On the contrary, as narrow- 

 leaved crops are highly exhausting, the more par- 

 ticulai-ly when they are allowed to mature their 

 seeds ; and these seeds and much of their other pro- 

 ducts are removed from the soil, they have been 

 denominated exhausting crops. With a know- 

 ledge of these principles, and of the character of 

 the plants which he cultivates, the agriculturist is 

 enabled to maintain a proper degree of fertility in 

 his soil. If his land be poor, "he will cultivate 

 more ameliorating and fewer exhausting crops, un- 

 til it is sufficiently enriched. If sufficiently en- 

 riched, he will maintain it in that state by his 

 ameliorating crops, which are a source of manure 

 to restore to the soil, those principles of vegeta- 

 tion which have been subtracted from it by the ex- 

 hausting crops. This is to be accomplished either, 

 immediately, by ploughing in the ameliorating 

 crops; or mediately, by employing them as food 

 for cattle, and applying the products of the farm 

 yard in the form of manure. 



Tliis interchange of broad and narrow-leaved 



crops, constitutes one of the most important prin- 

 ciples of a rotation of crops. Its application to 

 practice is, however, to be modified by the circum- 

 stances which are about to be mentioned. 



We have just seen that vegetables are separa- 

 ted into two classes, in reference to the organs by 

 which they derive their food from the atmosphere. 

 The same utility results from a classification with 

 respect to those by which they take it up from 

 the soil. Hence they have been divided into tap 

 and tuberous, and fibrous rooted plants. The 

 roots of the first class penetrate far into the earth, 

 subtract their nourishment principally at a great 

 depth, and divide the soil by their mechanical ac- 

 tion. The latter extend themselves near the sur- 

 face, draw their Ibod from it, and tend to bind the 

 soil. It results from the different action of these 

 two systems of roots, that their interchange will 

 be mutually advantageous; and that an economy 

 of manure will be obtained by it, for when the 

 surface of the soil becomes exhausted and unable 

 to support the fibrous rooted crop, its subtratum 

 may still afford an abundant pasture to plants ca- 

 pable of reaching it, by their tap or tuberous roots. 



But independently of the quality in vegetables 

 of withdrawing more or less of their nourishment 

 from the soil, in consequence of the peculiar struc- 

 ture of their leaves and roots, experience has 

 proved that every plant has a habit of vegetation 

 peculiar to itself, which by its action on the soil, 

 after a certain period, renders it unfit to reproduce 

 that particular vegetable, until a restoration has 

 been effected of those peculiar principles of which 

 it has been exhausted. Experience has also 

 proved that, although a soil may be thus exhausted 

 and unfit to produce one vegetable, it may be still 

 in a state highly favorable to the growth of many 

 others. These facts are firmly established by the 

 change of plants which is incessantly renewing 

 and beautifying the vegetable covering of the 

 eartli; by the alternation of the trees of our forests, 

 so familiar to us all; by the succession of grasses 

 on meadoAvs ; and by the daily observation of all 

 practical agriculturists. But while the fact is 

 confirmed beyond the possibility of doubt, it is to 

 be regretted that this is one of the secrets of vege- 

 tation upon which scientific research has shed the 

 least light. In lamenting the want of that clear 

 perception of principles, which is so necessary to 

 the direct and useful application of knowledge, it 

 is, however, satisfactory, that enough has been es- 

 tablished to prove that in the interchange of plants 

 of different habits of vegetation, there is a positive 

 economy of the alimentary principles contained in 

 the soil ; and consequently that by it a greater pro- 

 duct can be drawn from a given amount of ma- 

 nure, than by the continued culture of the same 

 plant. 



The effect of plants in exhausting the soil of 

 those principles peculiarly adapted to their sup- 

 port, will obviously be greater the longer they 

 have been cultivated. And in whatever way 

 those principles are restored, it is evident that the 

 time taken to accomplish it, will bear a ratio to 

 that in which they have been exhausting. It is 

 also evident that, if the recurrence of the same 

 plant, on the same field, proves injurious, the suc- 

 cession of those approaching each other in charac- 

 ter will also be so, to an extent, varying with their 

 greater or less affinity. 



From these views results one of the leading 



