162 CALCAREOUS WITH VEGETABLE MATTER. 



The fact that the effects of calcareous manures so generally ex- 

 ceed in measure the supposed power and operation of the causes, 

 and more especially in regard to neutral soils, seemed to indicate 

 that calcareous manures possessed other fertilizing powers, be- 

 sides those set forth in Chapter VIII. This, which formerly was 

 stated as a probability, may now be considered as certain. Evi- 

 dence of such effects, and of the supposed auxiliary and lately 

 known causes, will hereafter be presented. Dismissing them from 

 consideration for the present, I will return to stating the results of 

 applying marl as they have occurred almost without exception in 

 my own earlier practice, and which are confirmed by the con- 

 currence of all known and certain testimony in regard to practical 

 operations in the marl region of Virginia.] 



Under like circumstances in other respects, the benefit derived 

 from marling will be in proportion to the quantity of vegetable or 

 other putrescent matter given to the soil. It is essential that the 

 cultivation should be mild, and that little or no grazing be per- 

 mitted on poor lands under regular tillage, and which have no 

 supply of putrescent manure, except the grass and weeds growing 

 on them while at rest. Wherever farm-yard manure is used, the 

 land should be marled heavily ; and if the marl is applied first, so 

 much the better. The marl cannot act by fixing the other manure, 

 except so far as they are in contact, and when both are well mixed 

 with the soil. 



[When I first asserted the agency and force of calcareous ma- 

 nures in fixing alimentary manures in soils, and maintained the 

 great and indispensable^ necessity of that operation, the proposition 

 was founded almost exclusively on reasoning, and on observation 

 of natural soils, and not at all on practical effects then experienced 

 from applications of marl or lime. From the very nature of the 

 case, such effects as these, however important and valuable, could 

 not be seen at first, nor fully even in a very few years after begin- 

 ning to marl, nor their extent be understood and appreciated. 

 Moreover, my earlier experience had shown so fully the incapacity 

 of my acid or naturally poor soils to retain alimentary manures, 

 and my labours and expenditures to apply them had been so very 

 unprofitable, that I was not myself prepared for the full extent of 

 the contrary operation, after marl had been applied. And though 

 the views and estimation of such new operation have been yearly 

 enlarging, from the experience of practical results, still my esti- 

 mate of the fixing value of marl fell short of what is now confi- 

 dently believed, and which is every season manifest, of the greater 

 effect and permanency, and far greater profit of alimentary ma- 

 nures, caused solely by the presence of calcareous earth in the 

 same soils. Notwithstanding that the theory of the action of cal- 

 careous manures, as set forth in this essay, and published as early 



