234 SCIENCE OF GARDENING. PART II. 



broken down : and as soon as the most exhausting crop is taken, recent manure is again 

 applied. Peas and beans, in all instances, seem well adapted to prepare ground for 

 wheat ; and in some rich lands they are raised in alternate crops for years together. 

 Peas and beans contain a small quantity of a matter analogous to albumen ; but it seems 

 that the azote, which forms a constituent part of this matter, is derived from the atmo- 

 sphere. The dry bean-leaf, when burnt, yields a smell approaching to that of decomposing 

 animal matter ; and in its decay in the soil, may furnish principles capable of becoming 

 a part of the gluten in wheat. Though the general composition of plants is very analo- 

 gous, yet the specific difference in the products of many of them, prove that they must 

 derive different materials from the soil ; and though the vegetables having the smallest 

 system of leaves will proportionably most exhaust the soil of common nutritive matter, 

 yet particular vegetables, when their produce is carried off, will require peculiar princi- 

 ples to be supplied to the land in which they grow. Strawberries and potatoes at first 

 produce luxuriantly in virgin mould, recently turned up from pasture ; but in a few 

 years they degenerate, and require a fresh soil. Lands, in a course of years, often cease 

 to afford good cultivated grasses ; they become (as it is popularly said) tired of them ; 

 and one of the probable reasons for this is, the exhaustion of the gypsum contained in the 

 soil." 



1109. T/ie powers of vegetables to exhaust the soil of the principles necessary to their 

 growth, is remarkably exemplified in certain funguses. Mushrooms are said never to 

 rise in two successive seasons on the same spot ; and the production of the phenomena 

 called fairy rings has been ascribed by Dr. Wollaston to the power of the peculiar fungus 

 which forms it, to exhaust the soil of the nutriment necessary for the growth of the 

 species. The consequence is, that the ring annually extends ; for no seeds will grow 

 where their parents grew before them ; and the interior part of the circle has been ex- 

 hausted by preceding crops ; but where the fungus has died, nourishment is supplied for 

 grass, which usually rises within the circle, coarse, and of a dark green color. 



1110. A rotation is unnecessary, according to Grisenthwaite ; and, in a strict chemical 

 sense, what he asserts cannot be denied. His theory is a refinement on the common 

 idea of the uses of a rotation stated above ; but by giving some details of the constituent 

 parts of certain grains and certain manures, he has presented it in a more clear and 

 striking point of view than has hitherto been done. To apply the theory in every case, 

 the constituent parts of all manures and of all plants (1st, their roots and leaves, and, 

 2dly, their seeds, fruits, or grains,) must be known. In respect to manures this is the 

 case, and it may be said to be in a great degree the case as to the most useful agri- 

 cultural plants ; but, unfortunately for our purpose, the same cannot be said of garden 

 productions in general, though no branch of culture can show the advantage of a rota- 

 tion of crops more than horticulture, in the practice of which it is found that grounds 

 become tired of particular crops, notwithstanding that manures are applied at pleasure. 

 If the precise effects of a rotation were ascertained, and the ingredients peculiarly neces- 

 sary to every species pointed out, nothing could be more interesting than the results of 

 experimental trials ; and whoever shall point out a simple and economical mode by which 

 the potatoe may be grown successively in the same soil, and produce annually, neglecting 

 the effects of climate, as (iry and well-flavored tubers, or nearly so, as they generally pro- 

 duce the first and second years on a new soil, will confer a real benefit on society. That 

 wheat may be grown many years on the same soil by the use of animal manures, or such 

 as contain gluten, Grisenthwaite's theory would justify us in believing chemically ; and it 

 ought to be fairly tried by such cultivators as Coke and Curwen. Till this is done in 

 the face of the whole agricultural world, and the produce of every crop, and all the par- 

 ticulars of its culture, accurately reported on annually, the possibility of the thing may 

 be assented to from the premises, but will not be acted on ; and, in fact, even the best 

 agricultural chemists do not consider that we are sufficiently advanced in that branch of 

 the science to draw any conclusion, a priori, very much at variance with general opinion 

 and experience. 



CHAP. II. 

 Of Manures. 



1111. Every species of matter capable of promoting the growth of vegetables may be con- 

 sidered as manure. On examining the constituents of vegetables, we shall find that 

 they are composed of oxygen, hydrogen, carbon, and nitrogen, or azote, with a small 

 proportion of saline bodies. It is evident, therefore, that the substances employed 

 as manure should also be composed of these elements, for unless they are, there will 

 be a deficiency in some of the elements in the vegetable itself; and it is probable 

 that such deficiency may prevent the formation of those substances within it, for which its 



