712 



THE FARMERS' REGISTER. 



From tlie Loudon F.iriners' Magazine, December, 1841. 

 OF THE SUPPLY OF NITKIC ACID TO PLANTS. 



(^From Professor Johnstone's Lectures.) 



Fnregard to the aclion of nitric acid upon vege- 

 laiion, it is known — 



1°. That when, in the form of niirates of soda, 

 potash, &c., it is spread upon the soil, it greatly 

 pronioies (he growth and luxuriance ol' the crop, 

 and increases its produce ; and 



2'-\ Thai, vvheii other circumstances are favor- 

 able to vegetation — as in certain districts m India 

 — the presence ol'an appreciable quanuiy of these 

 niirates adds largely to the leniliiy ol the soil.* 



The same eHecis are unquestionably produced 

 by the addition of ammonia or by its natural pre- 

 sence in the soil. Tlie beneficial inliuence of boih 

 compounds, then, being recognized, the relative 

 extent to which each operates upon the general 

 vegetation of the globe wdl be mainly determined 

 by the circumstances and the quantity in which 

 Ihey respectively exist or are reproduced. 



In regard to the existence of niiric acid, it is not 

 known to form a necessary constituent of any of 

 the solid rocks of which the crust of ilie giobe_is 

 composed, but it is diflused almost nniversaliy 

 through the soil which overspreads the surface. 

 In the hotter regions of the earth, in India, in 

 Africa, and in South America, it in many places 

 accumulates in sufficient quaniiiy to Ibrm incrus- 

 taifons of considerable thickness over very large 

 areas, and in many more it can be separated by 

 washing the soil. Even in the climates of North- 

 ern Europe, it is rarely absent Irom the water of 

 artificial wells, into which the rains, after filtering 

 through the surlace, are permitted to make their 

 way.t 



* For the following, and other interesting notices, 

 regarding Indian agriculture, I am indebted to Mr. 

 Fleming of Barochan, in Renfrewshire, whose long 

 residence in the districts to which he alludes, as 

 well as the interest he- takes in practical agriculture, 

 renders his testimony very valuable: — 



" The districts of Chaprah, Tirhoot, and Shaha- 

 bad, near Patna, where a large proportion ot the 

 salpetre sent from BengaL is produced, are con- 

 sidered the most fertile in Bengal, producing two and 

 sometimes three crops yearly. The natives of these 

 districts, particularly a caste called Quirees) here- 

 ditary gardeners), who cultivate the best land, and 

 produce the best crops, are in the habit of irrigating 

 their fields with water from wells so strongly im- 

 pregnate<l with salpetre and other salts as to be 

 quite brackish, and they consider onions, turnips, 

 and peas, most benefited by this irrigation. Grain 

 crops also grow most luxuriantly on lai.ds yielding 

 saltpetre, where there is enough of rain within a 

 week or two after the seed is sown, but if a drought 

 follows the sowing, and continues for three weeks or 

 a month, the leal becomes yellow, and the crop fails. 



"The Hindoos do not generally manure their lands, 

 as the dung of the cattle is used for fuel, but the 

 Quirees collect the p.shes of cow dung and of burned 

 wood, and use it as a manure in some cases, chiefly 

 foi- the poppy plant. 



"The Hindoos have for ages been well acquainted 

 with the rotation of crops, and the advantage offal- 

 lowing land, — although a great proportion ot the land 

 is almost constantly in rice, Indian corn, or millet, 

 during the rainy season, and in wheat or peas during 

 the dry season." 



t It occurs in the wells of the neighborhood of 

 Berlin, (Milscherlich,) in the form of nitrates of 



On the whole, nitric acid and its compounds 

 appear to exist, ready formed, in nature, in larger 

 quantity than either ammonia or any of its com- 

 pounds. 



Of these nitrates, as they do of ammonia, the 

 rivers must be continually bearing a portion to the 

 s_pa, but there are in nature unceasing processes 

 of re|)roduction, by which not only this waste of 

 the nitrates is repaired, but that further waste 

 also, which is caused by iherr absorption in the 

 roots and subsequent decomposition in the interior 

 of plan's. Let us shortly consider these processes 

 of reproduction. 



1°. When a succession of electric sparks is 

 passed through common air, niiric acid (N O5) is 

 slowly but sensibly formed. The currents of 

 electricity which in nature traverse the atmo- 

 sphere must produce the same effecl, and the pas- 

 sage of each flash of lightning through the air 

 must be attended by the formation of some portion 

 of this acid. 



Alter a thunder-storm, plants appear wonder- 

 fully refreshed ; in thundery weather they grow 

 mosfluxuriantly, and other things being equal, 

 ihose seasons in which there i.=i much thunder are 

 observed to be most fruitful. Some have ascribed 

 these results to the immediate agency of electricity 

 on the growth of plants,* Is it not equally pos- 

 sible that they may be connected with this neces- 

 sary production of nitric acid 1 



In the rain which fell during seventeen thunder 

 storms, Liebig Ibund nitric acid always present, 

 and generally in combination with lime and am- 

 monia. In the rain which fell on sixty other 

 occasions, he could detect it only twice. In 

 minute quantity niiric acid is difficult to delect. 

 How much,, then, must be formed in a thunder 

 storm, even in our climate, to make the presence 

 of this acid rtZujai/s appreciable in the rain that 

 lalls — how vast a quantity in those warmer cli- 

 mates where such storms are so frequent and so 

 appallinir ! 



2°. When a mixture of aminonia with oxygen 

 gas is exploded by passing an electric spark 

 through ii, a quantity of nitric acid is formed, 

 even when the oxygen is not sufficient to oxidize 

 the whole of the ammonia t (Bischof). Hence, 

 if in the air, as we have seen reason to believe, 

 the ammonia given off from decaying animal mat- 

 ters, anil from other sources, be decomposed by 

 the atmospheric electricity, there will necessarily 

 be formed at the same instant a portion of nitric 

 acid, at the expense of the nitrogen of the am- 

 monia iiseif. This nitric acid will, as necessarily, 

 combine with some of the ammonia which still 

 remains in the air. Hence the existence ;md pro- 

 duction of nitrate of ammonia in the atmosphere, 

 and the consequent presence ol this acid along 

 with ammonia in rain water. 



potash, lime, and magnesia, in the wells round 

 Stockholm, and may be expected in all wells that are 

 dug (Berzelius^. — Traite de Chemic, iv. p. 71. 



* Sprengel, Chemie, i. p. 99. 



t It was shown above, that one of ammonia N Hs 

 requires three of oxygen to decompose it, lorming 

 3 of water, and setting the nitrogen free. But, in 

 reality, as Bischof has shown, the nitrogen is not 

 wholly set free, but a portion both of its hydrogen 

 and nitrogen combine with oxygen (are oxidized) at 

 the same instant, forming simultaneously both water 

 (HO,) and nitric acid (N O5) 



