446 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



too heavily. Many persons, for the purpose of removing para- 

 sitic plants, or getting thistles out of the land, salt so heavily as 

 to stop all vegetation. It may be done fearlessly ; for although 

 large applications of salt will render the land sterile for one year, 

 it may be brought into cultivation the next season by a slight 

 topdressing of lime. Some of the marls of New Jersey, contain- 

 ing large amounts of copperas, are treated empirically with lime, 

 sometimes to so great an extent that salt is required to counter- 

 act its effects. 



The proper quantity of salt to be applied depends materially 

 upon the condition of the soil ; in coming in contact with the 

 various alkalies in the soil, the muriatic acid of the salt is taken 

 up and the soda set free, which takes up carbonic acid from the 

 atmosphere and becomes carbonate of soda. I have found five 

 bushels to the acre to be entirely sufficient. The lime and salt 

 mixture may be used even recklessly, because any excess appears 

 quite inert. I have used it extensively to correct the injurious 

 effect of hog-pen manure when applied to the brassica tribe. 



Me. Fuller. — How much salt is required to destroy vegetation? 



Prof. Mapes. — Sometimes twenty-five bushels to the acre, and 

 sometimes one hundred. I have put at the rate of one hundred 

 and fifty bushels upon asparagus beds, to kill the weeds, and 

 would occasionally find one to escape. Asparagus is not injured 

 by salt ; it will grow up through half an inch of it. One hun- 

 dred bushels to the acre may be thrown upon a bed intended for 

 strawberries, and the next year the land will be found uninjured. 



I should recommend, as a precautionary measure, before again 

 using the land, to throw a little caustic shell lime over the sur- 

 face, to find its way down by the dews and rains. 



The form of the ultimate particles of lime, in the division 

 consequent upon slaking, is quite peculiar ; and it will pass down 

 through the soil with great rapidity. Thus, if you place upon 

 the top of a barrel of soil a dressing of lime, after making a 

 hole in the bottom of the barrel, and pass a stream of water 

 through it, in a single month you will find the lime upon the 

 lower head of the barrel. A heavy dressing of lime at long 

 intervals of time is wrong, because lime will pass down through 

 the soil and arrange itself upon the sub-soil. In under-draining 

 my present farm, I found in some places a white streak upon the 

 surface of the sub-soil, rendering it, from its admixture with the 

 Bub-soil, quite impervious to water or atmosphere passing down 



