7-2 



AGRICULTURAL CHEMISTRY. 



J.he anh.ial manures,, which act by their in- 

 organic ingredients. According to Berthier, 

 100 parts of the ashes of wheat straw con- 

 tain 



Of matter soluble in water - - 9*0 



Of matter insoluble in water 81 '0 



Now 100 parts of the soluble matter con- 

 tain 



Carbonic acid -a trace 



Sulphuric acid ... 2'0 



Muriatic acid . . . 13-Q 



Silica - - . - 35-0 



Votash and Soda ... 50.0 



100-0 



100 parts of the insoluble matter contain 

 Carbonic acid - - , 



Phosphoric acid 1*2 



/ C1*l* 



'Silica 

 Lime - , 



Oxide of Iron and Charcoal 

 Potash 



75.0 

 5-8 

 10-0 

 8-0 



100.0 



The silicate of potash employed in the 

 preparation of the compost described above 

 must not deliquesce on exposure to the air, 

 but must give a gelatinous consistence to 

 the water in which it is dissolved, and dry 

 to a white powder by exposure. It is only 

 attractive of moisture when an excess of 

 potash is present, which is apt to exert an 

 injurious influence upon the tender roots of 

 plint^. In those cases where silicate of 

 j)ut;ish cannot be procured, a sufficiency of 

 wood ashes will supply its place.* 



All culinary vegetables, but particularly 

 the cruciferae, such as mustard, (sinams 

 alba and nigra,) contain sulphur in notable 

 quantity. The same is the case with turnips, 

 the different varieties of rape, cabbage, 

 celery, and red clover. These plants thrive 

 best in soils containing sulphates ; hence if 

 these salts do not form natural constituents 

 of the soil, they must be introduced as ma- 

 nure. Sulphate of ammonia is the best 

 salt for this purpose. It is most easily pro- 

 cured by the addition of gypsum or sulphate 

 of ironf (green vitriol) to putrefied urine. 



* In some parts of the grand-duchy of Hesse, 

 where wood is scarce and dear, it is customary 

 for the common people to club together and build 

 baking ovens, which are heated with straw instead 

 of wood. The ashes of this straw are carefully 

 collected and sold every year at very high prices. 

 The farmers there have found by experience that 

 the ashes of straw form the very best manure for 

 wheat ; although it exerts no influence on the 

 growth of fallow-crops (potatoes or the legumi- 

 nosae. for example.) The stem of wheat grown 

 in this way possesses an uncommon strength. 

 The cause of the favourable action of these asnes 

 will be apparent, when it is considered that all 

 corn-plants require silicate of potash ; and that 

 the ashes of straw consist almost entirely of this 

 compound. ED. 



t If sulphate of iron be emploved, it ought not 

 to be added in great excess, and the urine must 

 be exposed to the air for some time after, for the 

 purpose of converting the iron into the peroxide. 

 A salt of the protoxide of iron is injurious to 

 vegetation. 



Horn, wool, and hoofs of cattle, contain 

 sulphur as a constituent, so that they will 

 be found a valuable manure when adrninis 

 tered with sqluble phosphates, (with urine, 

 for example.) 



Phosphate of magnesia and ammonia 

 forms the principal inorganic constituent of 

 the potato ; salts of potash also exist in it, 

 but in very limited quantity. Now the soil 

 is rendered unfitted for its cultivation, even 

 though the herb be returned to it after the 

 removal of the crop, unless some means are 

 adopted to replace the phosphate of magnesia 

 removed in the bulbous roots. This is best 

 effected by mixtures of night-soil with bran, 

 magnesian limestone, or the ashes of certain 

 kinds of coal. I applied to a field of pota- 

 toes manure, consisting of night- soil and 

 sulphate of magnesia, (Epsom salts,) and 

 obtained a remarkably large crop. The ma- 

 nure was prepared by adding a quantity ol 

 sulphate of magnesia to a mixture of urine 

 and faeces, and mixing the whole with the 

 ashes of coal or vegetable mould, till it ac- 

 I quired the consistence of a thick paste, 

 which was thus dried by exposure to the 

 sun. 



It has been formerly mentioned, that the 

 secondary and tertiary limestones contain 

 potash : marl, and the calcareous minerals 

 used for the preparation of hydraulic mortar, 

 may be particularly specified. These have 

 been found to form excellent manures for 

 heavy clayey soils, particularly for such as 

 disintegrate with difficulty. They are most 

 efficacious when burnt, but can only be ap- 

 plied in this state after harvest, and ought 

 to be ploughed into the soil as quickly aj 

 possible. By the action of lime upon clay, 

 the potash contained in the latter is rendered 

 soluble. This may easily be shown by mix- 

 ing one part of marl with half its weight of 

 burned lime, adding water, and setting aside 

 the mixture to repose for some time. Even 

 after a space of 24 hours, an appreciable 

 quantity of potash may be detected in the 

 water.* 



A most striking proof of the influence of 

 potash upon vegetation has been furnished 

 by the investigations of the " administration" 

 of tobacco in Paris. For many years accu- 

 rate analyses of the ashes of various sorts 

 of tobacco have been executed, by the orders 

 of the " administration ;" and it has been 

 found, as the result of these, that the value 

 of the tobacco stands in a certain relation to 



* One of the causes of the advantages produced 

 by subsoil ploughing is, that it exposes the soil to 

 the disintegrating influences of the atmosphere. 

 Hence it is that the subsoil plough is so beneficial 

 in siliceous soils, and exerts no apparent effect 

 upon those which contain much clay. The former 

 disintegrate and liberate their potash both with 

 facility and rapidity ; whilst the disintegration of 

 the latter proceeds with slowness, and no appre- 

 ciable effects are produced. (See Journal of the 

 Agricultural Society, vol. ii., p. 27.) It is proba- 

 ble, however, that if the land received a dressing 

 of lime after subsoil ploughing, the eFects would 

 be produced more rapidly. ED. 



