172 



On the Preparation and Use of Manures. Vol. VIII. 



ful influence on plants, and is one of the 

 most valuable of all our mineral fertilizers. 

 Much variety of opinion has been enter- 

 tained respecting the manner in which it 

 exerts its influence or produces its eflTects 

 on plants ; and these opinions can scarcely 

 be said to be harmonized, even at the pre- 

 sent time. Davy was inclined to consider 

 it a direct food for the plant, as it is found 

 to some extent, in those plants on which ii 

 exerts the most power. Cliaptal referred 

 its power to its stimulating agency on plants, 

 produced by its action when dissolved in wa- 

 ter. Liebig ascribes its value to its giving 

 a fixed condition to the nitrogen or ammo- 

 nia which is brought into the soil, and which 

 is indispensable for the nutrition of plants. 

 Dana, to the action of the lime and acid of 

 which the gypsum is composed, on the or- 

 ganic matter and silicates of the soil. He 

 says : — " It seems almost incredible, that so 

 minute a portion of a mineral can act at all; 

 yet how beautifully is the result explained 

 by the principle, that plants decompose first 

 this salt ; the lime, for plaster is a sulphate 

 of lime, then acts on geine, which is thus 

 rendered soluble ; while the acid, the oil of 

 vitriol or sulphuric acid, immediately acts 

 on silicates." It seems very probable, that 

 no single one of these suppositions will be 

 found able to account in full for the action 

 of plaster. That of Dr. Dana, appears to 

 approach as nearly to a solution as any of 

 them, if we extend his term silicates, so as 

 to embrace those combinations formed by the 

 union of the acid of the gypsum with am- 

 monia, after its separation from the lime. If 

 the action of plaster was due to its fixing 

 ammonia alone, then it ought to be equally 

 efficient at all times and places, which it 

 certainly is not; or if it acted directly as 

 nutriment, then its action would be as con- 

 stant as that of rotted manure or compost, 

 which farmers well know is not the case. 

 Plaster does not act as useliilly in the vi- 

 cinity of the sea, as in the interior; and on 

 heavy wet soils, is scarcely felt at all. Light 

 sandy soils, or loamy ones, are those on 

 which plaster acts the most sensibly ; and 

 clover, lucerne, potatoes, cabbages, and the 

 leguminous plants, such as peas, vetches, 

 &c., are the vegetables on which it exerts 

 the most powerful influence. It is much 

 valued as a dressing for wheat, not so much, 

 perhaps, for its direct action on that plant, 

 although that is not trifling, as for its effect 

 in securing and promoting the growth of 

 the clover and other grass seeds, usually, in 

 wheat countries, sown with this crop. So 

 marked is the influence it exerts in this re 

 spect, that plaster, clover, and wheat, are 

 always associated in the mind of the most 



successful wheat growers; and its use is the 

 most extensive in the best wheat growing 

 districts of our country. In the minds of 

 many, a senseless prejudice has existed 

 against plaster, on the ground that it the 

 more speedily exhausts the soil, and that 

 the heavy crops at first obtained, were the 

 price of ruined farms. It is doubtless true, 

 that the man who uses plaster on his farm, 

 who takes from liis soils all he can get, and 

 returns nothing to them, will soon find his 

 soils worthless enough. He who intends to 

 farm it in this way, should avoid plaster; 

 but let any farmer alternate wheat and clo- 

 ver; husband and apply his manures; feed 

 off his clover in his fields, or to his stock in 

 their stalls; let him not spare his grass 

 seeds in seeding, or his plaster in dressing, 

 and his farm will never run down. Such a 

 man need not fear plaster. 



Salt. — Common salt is an active and valu- 

 able manure, and has been used successfully 

 as sucli, in all parts of the world where it 

 can readily be obtained. In England, the 

 pickings or impure salt, is used for this pur- 

 pose ; and many experiments are on record, 

 to show that the eifect is most marked and 

 decisive. The following is one of a series 

 of experiments instituted by Mr. Sinclair, 

 to test the value of salt as a manure. The 

 soil was light and gravelly. 



No. 1. Soil without any manure for 4 years. Pro- 

 duce per acre, 13 bushels 26 lbs. 



No 2. Soil manured with stable dung to the preri- 

 us crop, (potatoes.) Produce per acre, 26 bushels 

 52 lbs. 



No. 3. Soil with five bushels of salt per acre, and 

 no other manure for 4 years. Produce per acre, 26 

 bushels 12 lbs. 



In the opinion of Mr. Sinclair, the effect 

 of salt as a manure was to lessen the pro- 

 duce of straw as compared with other ma- 

 nures, and to increase the weight of the 

 grain. 



Prof. Johnston has done more than any 

 other person to extend the use of salt as a 

 manure, by giving to the world his excellent 

 Essay on salt used on soils, and the mass of 

 experiments he has recorded. It appears 

 that salt in small proportions, promotes the 

 decomposition of animal and vegetable sub- 

 stances; that it destroys vermin and kills 

 weeds; that it is a direct constituent of 

 some plants, and therefore necessary to their 

 perfection ; that all cultivated plants of ma- 

 rine origin contain it, asparagus for instance; 

 and that all such succeed better when wa- 

 tered with salt water, than when deprived 

 of it; that salt preserves vegetables from 

 injury by sudden transitions in temperature, 

 salted soils not freezing as readily as those 

 to which salt has not been applied ; and that 



