AVERAGE PRODUCE PER ACRE. Ill 



which, in its combined forms of ammonia and nitric acid, is of 

 vast importance to the farmer. Of this elementary substance 

 plants generally contain only from 0*2 to 2 per cent., or at most 

 4 per cent. It is only in some leguminous plants, beans, and 

 pease that it reaches 3 or 4 per cent. The whole care of the 

 farmer, then, in all the manures which he applies, and in nearly 

 all his operations on the soil, is to provide his crops with suffi- 

 cient supplies of this relatively small amount of nitrogen in 

 proper condition, and of the above-named almost equally small 

 amount, relatively, of mineral matter, or ash as the chemist calls 

 it. He may apply to his land twenty tons of farmyard manure, 

 or five or six hundredweights of extraneous and more concen- 

 trated fertilising matter per acre ; the whole value in either case 

 consists in, and depends upon, the relatively small amount of 

 combined nitrogen and of mineral matter which the manure con- 

 tains : and if chemistry has taught us anything, it has taught us, 

 and proved beyond all question, that there is a close connection 

 between the composition of manures, of whatever kind, and of 

 the plants which they serve to nourish. 



It is manifestly of the utmost importance that we should 

 know and keep distinctly before us how much of this one 

 organic substance (nitrogen), and how much of this mineral 

 matter our eeveral crops require, — how much of them and how 

 much of each of tliem go to form, not 100 parts of this or 

 that vegetable product, but the whole crop of grain and straw, 

 turnips, or potatoes, that is usually produced upon, and removed 

 from, an acre of land. With tolerably satisfactory information 

 to guide us on this head (if it were properly understood and 

 applied), the indefatigable labours of chemists in this country 

 and on the Continent have now supplied us. But the form in 

 which it is commonly supplied has rendered it less available 

 and less useful to practical farmers than it might have been, and 

 has even led to a good deal of misunderstanding or misappre- 

 hension, not among farmers only, but even, in not a few cases, 

 among writers of papers and books on agricultural subjects. 



The mineral matter to which we have referred consists of nine 

 elementarv substances. Four others are occasionallv found in 

 certain })lants, but, being of no importance to the farmer, they 

 need not be named. Of these nine, only four or five are of 

 much importance as constituents of j)lants or manures, namelv, 

 phosphoric acid, potash, lime, magnesia, and sul[)hur, or sulphuric 

 acid. One of these again stands out from the rest as of para- 

 mount value and importance, namely, phosphorus or phosphoric 

 acid. (We shall not render what we have to say less acceptable 

 to tlie common reader by using the new cliemical ntunenclature, 

 phosphoric anhydride, kc.) Phosphoric acid, and ^s'itrogen (in 

 avaihalile form) are indeeel the two grand requisites in the 



