No. 3. 



Rotation of Ci-ops. 



97 



worm, muck-worm, and all other worms that 

 attack plants. I am led to this conclusion, 

 Mr. Editor, by numerous observations and 

 some experiments. I have found that where 

 there was the proper quantity of alkaline 

 substances plants were not injured by worms, 

 bugs, or flies, in any other way than by being 

 eaten up by them. And, indeed, tliey are 

 not so apt to be eaten when they have a 

 sufficiency of alkalies, for by their aid they 

 form carbonate of lime, phosphate of lime, 

 silicate of potash, «Sic., and make their stalks 

 and leaves so hard and strong as to be almost 

 impenetrable to the attacks of many insects 

 that infest them. And their juices are so 

 insipid that they are not so well relished by 

 such insects. 



Hoping, Mr. Editor, that my poor labours 

 may be of some service to my fellow men, I 

 take leave of you for the present. If my 

 services are acceptable, perhaps I may have 

 occasion often to write an article for your 

 paper. Yours, &,c., 



Chemico. 



Wilkesbarre, Pa., October 4tli, 1S45. 



Rotation of Crops. 



We take the following extract from Petzholdt's Ag- 

 ricultural Chemistry, as we find it published in the se- 

 cond number of the Farmers' Library. If this work, 

 BOW publishing by Greeley and McElrath,of New York, 

 .and edited by J. S. Skinner, does not sudBeed, it will 

 not be for lack of valuable matter, both original and 

 selected. — Ed. 



The practice of rotation of crops, has 

 arisen out of pure experience. The practi 

 cal farmer observed that, in most cases, when 

 the same plant was grown for two, three, or 

 more years consecutively upon the same 

 soil, it did not yield the same abundant har- 

 vest; whilst, when another crop was tried 

 upon that soil, the production was satisfac- 

 tory. Observation and experience subse- 

 quently and gradually established for differ- 

 ent parts a different alternation of crops, but 

 the practical agriculturist has never been 

 able to devise a fixed rule for every kind of 

 soil ; although many efforts have been made 

 to attain this desirable end, the subject has 

 not been able to pass the limit of mere em- 

 piricism. 



While the practical farmer wns content 

 to rest simply upon the facts supplied by his 

 experience, and remained satisfied with be- 

 lieving that some plants exhaust the soil, 

 while others do not, the theorist endeav- 

 oured to discover a key to this remarkable 

 phenomenon. Of all the hypotheses devised 

 to explain it, that of secretion and excretion 

 by the roots of plants, seems to have had the 



greatest number of adherents, because it ap- 

 pears to explain satisfiictorily the necessity 

 for the rotation of crops. 



According to this hypothesis, all plants 

 secrete or form certain matters during vege- 

 tation, which they cast out by their roots, 

 and the accumulation of these in the soil 

 exercises an injurious influence upon future 

 crops of the same plants, but does not inter- 

 fere with the growth of a different crop; nay, 

 it was further supposed that the excrements 

 of one species of plants might furnish an 

 appropriate nourishment for another species. 

 The framers of this hypothesis, no doubt, 

 imagined that plants in this respect exhib- 

 ited an analogy with animals, because we 

 see animals turn witb aversion from the e.v- 

 crements of their own species, whilst the 

 same excrements are sought and eagerly de- 

 voured by animals of a different species. 

 But this supposed analogy is utterly falla- 

 cious ; and if we examine the adaptation of 

 the hypothesis to the facts of the rotation of 

 crops, we shall find it to be altogether un- 

 satisfactory. 



The experiments made to prove that certain 

 matters are secreted by the roots of plants, 

 are by no means conclusive; but, since it is 

 well established that plants possess the power 

 of absorbing and adapting matter for their 

 growth, we may also suppose, in the ab- 

 sence of direct proofs, that they likewise 

 secrete matter by their roots. For brevity's 

 sake, we will admit that such secretion takes 

 place, and enquire into the proofs adduced 

 to render the opinion probable, that these 

 secretions exercise an injurious influence 

 upon the growth of plants of the same spe- 

 cies, whilst the same matter favours, or, at 

 least, does not exert any injurious effect 

 upon the growth and developement of plants 

 belonging to other species. 



The facts brought forward to establish 

 this theory are such as these — 1st. That 

 fruit trees, planted on the same spot where 

 previously others of the same species had 

 long grown, have not produced so well as 

 usual. 2nd. The camomile — malricaria 

 chamomilla — when, to a certain extent, pre- 

 sent in a field, interferes with the growth of 

 the cereals, owing, as it is supposed, to its 

 secretions in the soil being offensive to the 

 latter. 3rd. After the culture of peas, 

 vetches, clover, buckwheat, &c., far finer 

 crops of cereals will be produced than if 

 consecutive crops of grain were attempted. 



But, in objection to the theory of the ex- 

 cretions of one plant being injurious to an- 

 other, we might allege, that it often happens 

 that trees of the same kind will ffourish 

 upon spots where they have previously 

 grown ; and that in many countries, espe- 



