SIO 



MARL. 



M. Puvis does not by any means give the doses in this table as 

 those that should be invariably employed ; the table is one of aver- 

 ages, deduced from practical results, and tested by experience as 

 most truly useful. But special cases may occur that would make 

 departure from these conclusions not only advisable, but advantage- 

 ous.* 



The use of marl produces an unquestionable effect on the pro- 

 ductive properties of the soil. According to M. Puvis, the applica- 

 tion of the proper dose of a sandy marl, containing from 30 to 60 per 

 cent, of carbonate of lime, doubled the produce of a piece of parched 

 land in the department of the Isere. Before the application of the 

 marl nothing but dwarfish crops of rye were gathered, yielding at 

 most three for one of the seed ; at present, eight for one of seed, 

 and that wheat, are obtained ; and the good effects are found to 

 continue for ten and even twelve years. 



The action of marl is not unlimited any more than that of lime, 

 as the last sentence will give the reader reason to conclude. With 

 every harvest, a certain proportion of it is carried off, and the land 

 is finally left with an inadequate quantity of the calcareous element, 

 which then requires to be restored. The nature of the crop, how- 

 ever, has the most marked influence on the quantity of lime that is 

 taken up and carried away from the soil ; allowing the broadest 

 margin, and judging from the composition of the ashes of the plants 

 that form the subjects of our ordinary crops, we can see that the 

 quantity of 3| bushels of marl of the usual composition per acre, 

 which is assumed as the average quantity to be laid on, is vastly 

 more than can be absolutely necessary. 



Wood ashes contribute to improve the soil. They contain, besides 

 fiilica, both phosphate and carbonate of lime and alkaline sulphates, 

 phosphates, and carbonates. In a general way, every thing derived 



 Puvis in Annals of French AgricuUuro, vol. xxviii. p. 328, 2d series. 



