ALKALI. 



A few years after gypsum was introduced 

 into general use, farmers began to observe a 

 diminution of their hay crops, and to condemn 

 it as an exhauster of the soil. But this charge 

 against plaster was not well founded, at least 

 in the sense it was made. 



The numerous instances given by Liebig, 

 of the importance of the alkalies and metallic 

 oxides on vegetation, show that their influence 

 has been too much overlooked. It has been 

 thought remarkable by some vegetable physi- 

 ologists, that those cereal grasses which 

 furnish food for man, should, as it were, 

 follow him wherever he goes. The reason is 

 to be found in the fact, that none of our grain 

 plants can produce perfect seeds, or seeds 

 yielding farina, without a greater supply of 

 phosphate of magnesia and ammonia than 

 can be found in regions where these salts, 

 resulting from organized vitality, are less 

 abundant. (Cultivator.) 



Plants growing on a soil, containing a due 

 mixture of earthy ingredients, always select a 

 proportion of each, according to their several 

 capacities or wants. It is a fact of the highest 

 practical value to the agriculturist to know, 

 that where a soil which originally contained 

 all the elements essential to the production of a 

 crop, becomes exhausted of one alkaline or 

 earthy element, another may be substituted so 

 as to compensate for the privation. Where, 

 for example, there is a deficiency in a soil of 

 the alkaline earth lime, the addition of potash, 

 soda or magnesia, all of which exist in the 

 ashes of wood and other vegetable substances, 

 may be resorted to for the purpose of making 

 it up. Thus, plants when growing in a soil 

 where there is no potash will make up the 

 deficiency by taking up soda, if this last alkali 

 be present. 



Plants which grow on or near the sea-shore 

 assimilate or take up soda instead of potash. 

 Sea-salt consists almost entirely of soda, and 

 the sea is therefore to be regarded as the great 

 source of this alkali. It is, however, found in 

 England and many other countries in the form 

 of native rock salt, and also exists in most 

 soils combined with potash. The soda ot com- 

 merce is usually obtained from the ashes of 

 plants growing on the sea coast, just as potash 

 is procured from the ashes of trees and other 

 vegetables growing inland. (See Soda, Kelp,&c.) 



The sowing of the earth with salt has from 

 the earliest times been deemed an infallible 

 means of producing total barrenness, and the 

 excess of any salt in a soil is still known to 

 be destructive of fertility. 



The perfect developement of a plant is, never- 

 theless, according to Liebig, dependent on the 

 presence of due proportions of the alkalies or 

 alkaline earths, since, when these substances 

 are totally wanting, its growth will be arrest- 

 ed, and when they are only deficient it must 

 be impeded. "Let us compare," says this emi- 

 nent chemist, " two kinds of trees, the wood of 

 which contains unequal quantities of alkaline 

 bases, and we shall find that one of these 

 grows luxuriantly in several soils, upon which 

 the others are scarcely able to vegetate. For 

 example, 10,000 parts of oak wood yield 250 



ALKALI. 



parts of ashes, tne same quantity of fir-wood 

 only 83, of linden-wood 500, of rye 440, and 

 of the herb of the potato-plant 1500 parts. 



"Firs and pines find a sufficient quantity of 

 alkalies in granitic and barren sandy soils, in 

 which oaks will not grow ; and wheat thrives 

 in soils favourable for the linden-tree, because 

 the bases, which are necessary to bring it to 

 complete maturity, exist there in sufficient 

 quantity. The accuracy of these conclusions, 

 so highly important to agriculture and to the 

 cultivation of forests, can be proved by the 

 the most evident facls. 



" All kinds of grasses, the Equisetaceee, for 

 example, contain in the outer parts of their 

 leaves and stalk a large quantity of silicic acid 

 and potash, in the form of acid silicate of 

 potash. The proportion of this salt does not 

 vary perceptibly in the soil of corn-fields, be- 

 cause it is again conveyed to them as manure 

 in the form of putrefying straw. But this is 

 not the case in a meadow, and hence we never 

 find a luxuriant crop of grass on sandy and 

 calcareous soils which contain little potash, 

 evidently because one of the constituents in- 

 dispensable to the growth of the plants is 

 wanting. Soils formed from basalt, grau- 

 wacke, and porphyry are, caeteris paribus, the 

 best for meadow land, on account of the quan- 

 tity of potash which enters into their composi- 

 tion. The potash abstracted by the plants is 

 restored during the annual irrigation.* That 

 contained in Ihe soil itself is inexhaustible in 

 comparison with the quantity removed by 

 plants. 



"But when we increase the crop of grass in 

 a meadow by means of gypsum, we remove a 

 greater quantity of potash with the hay than 

 can, under the same circumstances, be restored. 

 Hence it happens, that after the lapse of seve- 

 ral years, the crops of grass on the meadows 

 manured with gypsum diminish, owing to the 

 deficiency of potash. But if the meadow be 

 strewed from time to time with wood-ashes, 

 even with the lixiviated ashes which have 

 been used by soap-boilers, (in Germany much 

 soap is made from the ashes of wood,) then 

 the grass thrives as luxuriantly as before. 

 The ashes are only a means of restoring the 

 potash. 



" A harvest of grain is obtained every thirty 

 or forty years from the soil of the Luneburg 

 heath, by strewing it with the ashes of the 

 heath-plants (Erica vulgaris) which grow on 

 it. These plants during the long period just 

 mentioned collect the potash and soda, which 

 are conveyed to them by rain-water ; and it is 

 by means of these alkalies, that oats, barley, 

 and rye, to which they are indispensable, are 

 enabled to grow on this sandy heath. 



* A very high value is attached in Germany to the 

 cultivation of grass as winter provision for cattle, and 

 the greatest care is used in order to obtain the greatest 

 possible quantity. In the vicinity of Liegen (a town in 

 Nassau), from three to five perfect crops are obtained 

 from one meadow, and this is effected by covering the 

 fields with river-water, which is conducted over the 

 meadow in spring by numerous small canals. This is 

 found to be of such advantage, that supposing a meadow 

 not so treated to yield 1,000 Ibs. of hay, then from one 

 thus watered 4,500 Ibs. are produced. In respect to the 

 cultivation of meadows, the country around Liegea is 

 1 considered to be the best in all Germany. L. 



63 



