MARL. 



599 



MARL. 



A LETTER ADDRESSED TO THE AGRICULTURAL SOCIETY OF JEFFERSON COUNTY, GA. 



BY J. H. HAMMOND. [Concluded from May No. 



The presence of lime is also known to influ- 

 ence the decomposition of the silicates of potash 

 and soda, and at the moment of decomposition, 

 both the silica and alkali are soluble. Thus, lime 

 aids materially in supplying those essential el- 

 ements to plants. Whether it does so by its al- 

 kaline properties, or by concentrating carbonic 

 acid, or merely by its catalytic power, has not 

 been settled. The silicate of lime itself, when 

 rendered soluble by the decomposing influence 

 of carbonic acid, sometimes, as I have stated, be- 

 comes, in their absence, a substitute for the sili- 

 cates of potash and soda. It is this combination 

 also, that renders light, sandy lands more consis- 

 tent, which is one of the most important effects 

 of lime oil such land.s — particularly on the light 

 uplands so extensively planted on this side of 

 the Savannah, and in your County. The fact is 

 unquestionable. It is usually referred, as is the 

 opening of stiff lands, to the nrechanical influ- 

 ence of the lime, but the cause assigned here, as 

 in tliat case, is not adequate to the effect. 



The red and brown lauds in your County are 

 colored, as they are everywhere else, by iron. — 

 You have no doubt observed, that after contin- 

 ued cultivation, some of the best of them cease 

 to become productive without much apparent 

 less of vegetable mould, and are not rapidly re- 

 stored either by rest or manure. Among other 

 causes, this is owing to a considerable extent, to 

 the excessive oxidation of the iron in conse- 

 quence of its exposure from plowing, to the at- 

 mosphere, whence it extracts o.xygen, a process 

 you see constantly exemplified by the rusting of 

 old iron. It becomes what is called a peroxide 

 of iron, which is very injurious to vegetation — 

 Lime neutralizes all acids, and if put upon these 

 lands in [)roper quantities, it will neutralize a 

 portion of the acid in the iron, and convert the 

 peroxide into a protoxide of iron, which, if not 

 actually beneficial, is at least harmle.ss to plants. 

 You have too, in some of your soils, the sulphur- 

 et of iron, so often taken for gold ore. This, on 

 exposure to air, absorbs oxygen, wliich produ- 

 ces sulphuric acid, and then forms the sulphate 

 of iron or copperas, which is poisonous to plants. 

 If lime is put on the land it will arrest the acces- 

 sion of the sulphuric acid thus formed to the iron, 

 and prevent the fomiation of copperas. Cut what 

 is more, combining with the sulphuric acid it- 

 self, it forms sulphate of lime, commonly called 

 pla.ster of Paris, one of the most highly prized of 

 all mineral manures, and an clement in all, or 

 nearly all plants. Lime has also the power of 

 forming plaster in the same way when it comes 

 in contact with the sulphate of silicon, which is 

 supposed to exist in all soils. It combines also 

 with sulphuric acid, arising from vegetable de- 

 composition or any other source, and produces 

 this valuable salt. 



The sulphate of lime, called also gypsum, as 

 well a.s plaster of Paris, must exist to some ex- 

 tent in all soils, as it is found in almo.st all plants. 

 {12.59) 



But, like the carbonate of lime, it is seldom to be 

 detected by chemical tests. It may also be elim- 

 inated from unknown combinations by the vital 

 action of the growing phuit. But in the way I 

 have mentioned, it will undoubtedly be formed 

 in greater abundance in all .soils, by the applica 

 tionoflime. Sulphuric acid itself is often used 

 as a manure, but experience has fully estab- 

 lished the fact, that it is of little value excejit on 

 calcareous soils ; and what is more remarkable, 

 that sulphate of lime will al.'^ act with far great- 

 er effect on limed lands. 1 tried some of it my- 

 self the past year on marled land. I rolled the 

 cottonseed in it, previously to planting them, 

 and thus applied it at the rate of only one peck 

 of the plaster per acre. I am satisfied that the 

 product, on the few acres to which it was ap- 

 plied, was one-third greater than on similar ad- 

 joining land, marled al.so, but not pla.stered. I 

 anticipate, therefore, the greatest benefit from 

 the use of plaster after marl. I should remark, 

 however, that it has not been found invariably 

 beneficial even on limed lands. In England, and 

 on our coa.st south of Long l.<land, little advan- 

 tage has been derived from it. Two probable 

 causes have been as.signed for this : the influence 

 of sea air, which has not been satisfactorily ex- 

 plained, and the probabihty that the lands in the 

 region mentioned have derived a sufficiency of 

 gypsum already from the sulphuret of iron, or 

 other sources. Very little is required for plants : 

 one peck per acre applied to the moistened .seed 

 will probably have as much ettect, tor one year 

 at least, as any other quantity. In the last dry 

 season, it had on my land double the efl'ect of a 

 bushel sown broadcast. Five to ten bushels are 

 sometimes applied. 



Phosphate of lime is even more esteemed for 

 a manure than the sulphate. It is sometimes 

 called the " Earth of Bones," as Iiones contain 

 over ."jO per cent, of this salt. Being less abun- 

 dant than sulphate of lime, it is much more cost- 

 ly. Bones are transported across the Atlantic to 

 England, to be used as manure. Several hun- 

 dred vessels are now engaged solely in trans- 

 porting bones from various parts of the world to 

 England. This phosphate is also an essential 

 constituent of plants, though rarely to be detect- 

 ed in soils. But phosphoric acid, like suljihur- 

 ic, arisi^s from vegetable decomposition, from 

 phosphuret of silicon, and perhaps other sources. 

 If lime be present in the soil to fix it. not only is 

 the vital action of the plant relieved from produ- 

 cing it, but much is probably saved that would 

 otherwise be lost. The ash of cottonseed con- 

 tains considerably more of this aci(i than bones 

 do, and hence the immense value of this seed as 

 a manure. But its effects are proverbially tran- 

 sient. With lime in the soil sufficiently abund- 

 ant to fix the phosphoric acid, cotton seed 

 would be a manure almost as permanent as 

 bones. But to detail all the operations of lime 

 in the soil, in assisting to prepare food for plants 



