58 ALKALIES m SOIL. 



lime contained in the straw, it will be seen that the actual 

 amount of lime and potash, in what is called poor soil, will 

 hardly begin to diminish at the end of a long lease, cropping 

 every year 30 bushels of wheat. Allowing thus, for exam 

 pie, the proportion of straw which such a crop would afford, 

 to be about 5000 lbs., and this is not far from the truth, the 

 straw gives 4.40 of its weight of ashes, or 220 lbs., of which 

 one-fifth is soluble in water, and one-half of that dissolved 

 is potash. The spent ashes, or that part not soluble in 

 water, contains 5.80 per cent, of lime. On these data, an 

 acre of wheat straw, or 2|- tons, will give 220 lbs. of ashes, 

 containing 22 lbs. of potash, and 10 lbs. of lime. The 

 potash will last at this rate for the straw, over 3000 years ! 

 It will be hereafter shown, that when the lime fails, the crop 

 will not. 



Since the first edition of this work appeared, numerous 

 ash analyses of rye have been made by the first chemists 

 and analysts of the day. Calculating the lime in rye on the 

 average of these results, 1000 lbs. of grain would give 23 

 lbs. of ashes. Of this amount, 1.145 lb. is lime; and even 

 at this rate the grain of 20 bushels of rye per year, from an 

 acre, would exhaust the soil of lime in the first six inches 

 from the surface, only in 3166 years. Allowing 4000 lbs. 

 •of straw annually, the lime in this is 11.25 lbs., equal to 322 

 annual crops, or the lime would last for the grain and straw 

 293 years. 



75. Were similar calculations extended to soil supposed to 

 be formed of any other rock, the amount of lime and alkali 

 would still be seen to be almost inexhaustible. And whether 

 rocks be supposed or not, to form the soil over them, it may 

 be established, as the fourth leading principle of agricultural 

 chemistry, that soils contain enough of all the mineral 



ELEMENTS, TO GROW ANY CROP. 



