140 TALKS ON MANURES. 



total aiiKJiint of mineral matters in the wheat produced from one 

 acre, only a trifling quantity of other and more valuable fertilizing 

 ash constituents of plants will be left. On comparing the relative 

 amounts of phosphoric acid, and potash, in an average crop of 

 wheat, and a good crop of clover-hay, it will be seen that one acre 

 of clover-hay contains as much phosphoric acid, as two and one- 

 half acres of wheat, and as much potasb as the produce from five 

 acres of the same crop. Clover thus unquestionably removes from 

 the land very much more mineral matter than does wbeat ; wheat, 

 notwithstanding, succeeds remarkably well after clover. 



" Four tons of clover -hay, or the produce of an acre, contains, as 

 already stated, 224 lbs. of nitrogen, or calculated as ammonia, 

 272 lbs. 



" Assuming the grain of wheat to furnish 1.78 per cent of nitrogen, 

 and wheat-straw, .64 per cent, and assuming also that 1,500 lbs. of 

 corn, and 3,000 lbs. of straw, represent the average produce per 

 acre, there will be in the grain of wheat, per acre, 26.7 lbs. of nitro- 

 gen, and in the straw, 19.2 lbs., or in both together, 46 lbs. of 

 nitrogen ; in round numbers, equal to about 55 lbs. of ammonia, 

 which is only about one-fifth the quantity of nitrogen in the pro- 

 duce of an acre of clover. Wheat, it is well known, is specially 

 benefited by the application of nitrogenous manures, and as 

 clover carries off so large a quantity of nitrogen, it is natural to 

 expect the yield of wheat, after clover, to fall sliort of what the 

 land might be presumed to produce without manure, before a crop 

 of clover was taken from it. Experience, however, has proved 

 the fallacy of tliis presumption, for the result is exactly the oppo- 

 site, inasmuch as a better and heavier crop of wheat is produced 

 than without the intercalation of clover. What, it may be asked, 

 is the explanation of this apparent anomaly ? 



"In taking up this inquiry, I was led to pass in review the cele- 

 brated and highly important experiments, undertaken by Mr. 

 Lawes and Dr. Gilbert, on the continued growth of wheat on the 

 same soil, for a long succession of years, and to examine, likewise 

 carefully, many points, to which attention is drawn, by the same 

 authors in their memoirs on the growth of red clover by different 

 manures, and on the Lois Wcedon plan of growing wheat. Abun- 

 dant and most convincing evidence is supplied by these indefatiga- 

 ble experimenters, that the wheat-producing powers of a soil are 

 not increased in any sensible degree by the liberal supply of all 

 the mineral matters, which enter into the composition of the ash of 

 wheat, and that the abstraction of these mineral matters from the 

 soil, in any much larger proportions than can possibly take place 



