1838] 



FARMERS' REGISTER. 



659 



employed, in which the soil is exposed to the air, 

 and submitted lo [)rocesses which arc purely me- 

 clianical, namely, folloiving. 



The benefits arising from fallows have been 

 much overrated. A summer liillovv, or a clean 

 fallow, may be sometimes necessary in lands over- 

 grown with weeds, particularly iC they are sands 

 which cannot be pared and burnt with advaniaije ; 

 but is certainly unprofitable as part of a. general 

 system in husbandry. 



h has been supposed by some writers, that cer- 

 tain principles necessary to fertility are derived 

 Irom the atmosphere, which are exhausted by a 

 succession of crops, and that these are a<rain sup- 

 plied during lite repose of the land, and the expo- 

 sure of the pulverized soil to ihe influence of the 

 air ; but this, as was mentioned in the introductory 

 lecture, is not a correct statement. Oxygen is 

 absorbed by the vegetable film, and, perhaps, in 

 certain cases, azote ; but the earths, the great ele- 

 ments of soils, cannot be combined with new ele- 

 ments from the air ; none of them unite to azote ; 

 and such of them, as are capable of attracting car- 

 bonic acid, are always saturated with it in those 

 soils on which the practiceof fallowing is adopted. 

 The vague ancient opinion of the use of nitre and 

 of nitrous salts in vegetation, seems to have been 

 one of the principal speculative reasons lor the 

 defence of summer fallows. Nitrous salts are 

 produced during the exposure of soils containing 

 vegetable and animal remains, and in greatest 

 abundance in hot weather ;* bur it is probably by 

 the combination of azote from these remains with 

 oxygen in the atmosphere that the acid is formed, 

 and at the expense of an element which other- 

 wise would fiave formed ammonia ; the com- 

 pounds of which, as is evident from what is stated 

 in the last lecture, are much more efficacious than 

 the nitrous compounds in assistiner vegetation. 



When weeds are buried in the soil, by their 

 absorption of oxygen and gradual decomposition 

 they furnish a certain quantity of soluble matter, 

 and a soil will certainly in consequence produce 

 better crops at the end of a fallow ; but the use of 

 this practice must depend upon the quantity of ve- 

 getable fibre and its nature, and upon the quality 

 of" the soil. Carbonic acid gas is formed durin<r 

 the whole time by the action of the vegetable 

 matter upon the oxygen of the air, and the greater 

 part of it is lost to the soil in which it was formed, 

 and dissipated in the atmosphere. 



The action of the sun upon the surface of the 

 soil tends to disengage the gaseous and the vola- 

 tile fluid matters that it contains; and heat in- 

 creases the rapidity of fermentation : and in the 

 summer fiillow, nourishment is rapidly produced, 

 at a time when no vegetables are present capable 

 of absorbing it. 



Land, when it is not employed in preparing food 

 for animals, should be applied to the purpose of 

 the preparation of manure for plants; and this is 

 effected by means of green crops, in consequence 



* Nitre and nitrate of lime are the two nitrous salts 

 of most common occurrence ; the presence of lime 

 appears to be essential to the production of both. In 

 situations, however favorable in other respects, in 

 which there is no potash pre-existing, there nitre will 

 not form ; nitrate of lime will appear alone. Nitre, 

 therefore, is chiefly confined to countries of primary 

 rock formations, containing feldspar or some analo2;oiis 

 mineral, which in decomposing yields potassa.— J. D. 



of the absorption of carbonaceous mailer in the 

 carbonic acid of the atmosphere. \n a sunmier'a 

 fallow a period is always lost in which vegetables 

 may be raised, either as fend for animals, or as 

 nourishment for the next crop ; and the texture of 

 the soil is not so much improved by it exposure 

 as in winter, when the expansive powers of ice, 

 the gradual dissolution of snovvs, and the alterna- 

 tions li-oin wet to dry, tend to pulverize it, and to 

 mix iis diderent parts together. 



In the drill husbandry the land is preserved 

 clean by the extirpation of the weeds by hand, 

 by raising the crops in rows, which renders the de- 

 struction of the weeds much more easy. Manure 

 is supplied either by the green crops themselves, or 

 Irom the dung of the cattle led upon them ; and 

 the plants having large systemsol leaves are made 

 to alternate with those bearing grain. 



!t is a great advantage in the convertible system 

 of cultivation, that the whole of the manure is em- 

 plo^'ed ; and that those parts of it which are not 

 fitted lor one crop remain as nourishment for an- 

 other. Thus, m Mr. Coke's course of crops, the 

 turnip is the first in the order of succession ; and 

 this crop is manured with recent dung, which im- 

 mediately affords sufficient soluble matter for its 

 nourishment; and the heat produced in ferment- 

 ation assists the germination of the seed and the 

 growth of the plant. After turnips, barley with 

 grass seeds is sown ; and the land, having been 

 little exhausted by the turnip crop, afl'ords the 

 soluble parts of the decomposing manure to the 

 grain. The grasses, rye-grass, and clover remain, 

 which derive a small part only of their organized 

 matter Irom the soil, and probably consume the 

 gypsum in the manure, which would be useless to 

 other crops : these plants, likewise, by their large 

 systems of leaves, absorb a considerable quantity 

 of nourishment from the atmosphere ; and when 

 ploughed in at the end of two years, the decay of 

 their roots and leaves afl'ords tnamire for the wheat 

 crop: and at this period of the course, the woody 

 fibre of thefiirm-yard manure, which contains the 

 phosphate of lime and the other difficultly soluble 

 parts, is broken down ; and as soon as the most 

 exhausting crop is taken, recent manure is again 

 applied. 



Mr. Gregg, whose ingenious system of culti- 

 vation has been published by the Board of Agri- 

 culture, and who has the merit of first adopting a 

 plan similar to Mr. Cok^'^s upon strong clays, suf- 

 fers the ground after barley to remain at rest for 

 two years in grass ; sows peas and beans on the 

 leys ; ploughs in the pea or bean stubble for 

 wheal ; and in some instances follows his wheat 

 crops by a course of winter tares and winter bar- 

 ley, which is eat off in the spring, before the land 

 is sowed for turnips. 



Peas and beans, in all instances, seem well 

 adapted to prepare the ground for wheat ; and in 

 some rich lands, as in the alluvial soil of the Par- 

 ret, mentione<l in the f()urth lecture, and at the 

 foot of the South Downs in Sussex, they are raised 

 in alternate crops for years together. Peas and 

 beans contain, as appears from the analyses in the 

 third lecture, a small quantity of matter analogous 

 to albumen ; but it seems that the azote, which 

 forms a constituent pari of this matter, is derived 

 from the atmosphert;. The dry bean leaf, when 

 burnt, yields a sine'l approaching to that of de- 

 composing aiiimal matter; and in its decay in the 



