No. 6. 



On the Preparation and Use of Manures. 



171 



establishing' tlieir positions. A knowledge 

 of the nature of the action of lime, would 

 have prevented such seeming contradictions. 

 " Lime in excess, forms, from the humiis of 

 the soil, an insoluble salt; and may thus, 

 when applied to a soil abounding in salts of 

 lime, or in which it already exists, be pro- 

 ductive of injury, whatever may be the ve- 

 getable or organic matter of the soil. In 

 this state of excess, lime converts, but at the 

 same time locks up, the humus of the soil ; 

 when, if applied in the right quantity, it 

 would have been useful. Lime is of no 

 value whatever, as a converter, or produces 

 no chemical effect in promoting growth, un- 

 less there is organic matter in the soil on 

 which it can act. Lime is most efficient 

 when used on soils full of insoluble humus, 

 such as peaty matter or woody fibre, but 

 which, from the abundance of the tannin 

 principle contained, resist the ordinary pro- 

 cesses of decomposition." There would 

 seem to be no difficulty, therefore, in deter- 

 mining whether lime can be used on any 

 given soil to profit. Indeed there are, it is 

 believed, none where it would not be useful, 

 except such as are already supplied with 

 this carbonate, or those which are wholly 

 destitute of vegetable or organic matter. 

 As a general rule, the greater the quantity 

 of humus in a soil, the greater the amount 

 of lime which may be applied witli benefit. 

 As long as there is a store of organic matter 

 in the soil, lime, if not in excess, is a valu- 

 able manure; but when this is exhausted, 

 the application of lime only increases the 

 sterility, by destroying such efforts at vege- 

 tation, as might in time, aided by light and 

 moisture, partially remove the unproductive- 

 ness existing. This fact may serve to ex- 

 plain some of the conflicting statements that 

 have appeared in the agricultural journals 

 of our country, on the use of lime. Where 

 humus is abundant, the quantity that may 

 be safely used, is very great ; on soils al- 

 ready poor, a small portion speedily exhausts 

 the remaining powers of the soil. Lime, 

 from its alkaline qualities, acts in neutral- 

 izing whatever free acids exist in soils, whe- 

 ther oxalic, phosphoric, malic, or others. It 

 acts also in decomposing some of the earthy 

 or compound salts formed in the soil, and 

 thus renders the geine held by them, avail- 

 able to the plant; but its great and most 

 important use is in converting the insoluble 

 organic matters existing, into soluble ones, 

 and thus directly furnishing an abundant 

 source of nutriment. Carbonate of lime is 

 sometimes used pounded or broken fine; and 

 in this state, its mechanical value is great 

 in stiff or clay soils. Such soils too, usually 

 abound in acids ; and these gradually acting 



on the lime gravel, its chemical effect is 

 slowly but beneficially apparent. 



Marl. — Marls, which exert so powerful 

 an influence on many soils, derive most of 

 their value from the lime they contain ; and 

 witli few exceptions, their power as fertil- 

 izers may be measured by the per cent, of 

 lime shown on analysis. There are some 

 marls, however, which are an exception to 

 this rule; their value appearing to depend 

 on other matters than mere lime. Of this 

 kind is the celebrated green sand marl of 

 New Jersey, and some other points of the 

 Atlantic coast. In this formation, which 

 acts so powerfully as a manure, there is 

 from six to ten per cent, of potash ; an 

 agent, which, on light soils, is scarcely 

 equaled as a manure. In addition to the 

 lime which marl contains, the influence of 

 the proportions of sand and clay, of which 

 tlie balance usually consists, must be taken 

 into consideration in determining the value 

 of this substance for particular soils. Thus, 

 on heavy or clay lands, marls abounding in 

 sand, will be found preferable to those the 

 base of which is clay ; and on light or sandy 

 soils, the latter will be much the most use- 

 ful, the per cent, of lime in both cases being 

 alike. JMarl should be spread over the sur- 

 face, and pulverized by the action of air and 

 fi-ost, before it is plouglied under. When 

 so treated, experience proves it is a most 

 valuable manure, and a single dressing ex- 

 erts an influence for many years. 



Phosphate of lime. — Of another salt of 

 lime, the phosphate, notice has been taken 

 when treating of bones as a manure. It 

 will not be amiss, however, to state here, 

 that when any substance is invariably found 

 in any part of a plant or plants, it is right 

 to infer that the perfection of that part of 

 the plant is impossible, unless the substance 

 required, is within reach of the plant while 

 growing. Thus the stems of the grasses 

 abound in silex ; some of them, the cane for 

 instance, to such a degree as to strike fire 

 with steel, and unless this substance, in the 

 form of silicates, was presented to the plants, 

 they w'ould not be perfect. So it is right to 

 infer, that unless soils contain the phos- 

 phates, or a supply is furnished for the use 

 of plants, that the cereal grains could never 

 be perfected, as the seeds of these invariably 

 contain large quantities of the phosphates. 

 Phosphates are found more or less in all 

 soils, and when these are deficient, bones 

 form an abundant and accessible source for 

 tlieir supply. It is also found in considera- 

 ble quantities in all animal and farm-yard 

 manures, particularly in the liquid part. 



Gypsum or plaster. — Gypsum is the third 

 principal salt of lime which exerts a power- 



