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CHAPTER XI. 



AMMOXIA AND NITRIC ACID. 



Source of the nitrogen of plants — Amount of ammonia and nitric acid in 

 rain and dew: Biueau, Boussingault, Knop — Quantity of ammonia in the 

 air — Quantity of nitrogenous food hrought to the soil yearly hy rain and 

 dew ; more present in the soil than is removed by the crops — The 

 generiU reason for decrease of productive power in soils — Classification 

 of manures according to the amount of nitrogen; assimilable and spar- 

 ingly assimilable nitrogen ; the niti-ogen theory ; only ammonia according 

 to this theory is wanting ; resemblance to the humus theory — Manuring 

 experiments with compoimds of ammonia by Schattenmann, by Lawes 

 and Gilbert, by the Agi-icultural Union of Munich, and by Kuhlmann — 

 The efficacy of a manure is not in proportion to its amount of nitrogen : 

 experiments — Large amount of nitrogen in soils ; the experiments of 

 Schmid and Pierre ; the arable siu-face soil contains most nitrogen — 

 Form of the ammonia in the soil ; Mayer's experiments — Comportment 

 of soil and farm-yard manure with the alkalies — The ineffective nitrogen 

 of the sod made effective by the supply of ash-constituents that are 

 wanting — Progress in agiiculture impossible if dependent on a supply 

 of ammoniacal compounds ; results of Lawes' experiments with salts of 

 ammonia — The artificial supply of ammonical manures contrasted with 

 the crops produced and the increase of popidatiiju — Increase of nitro- 

 genous food by natural means ; formation of nitrite of ammonia by oxi- 

 dation in the air according to Schonbeim — Supply of food in excess neces- 

 sary to produce corn-crops ; reasons — How the necessary excess of nitro- 

 genous food for com may be obtained from natural sources — The supply 

 of nitrogen in farm-yard manure in tlie Saxon experiments coiTosponded 

 to the crop of chner-hay — Loss of nitrogen in lime soils by oxidation ; 

 utility of a supply of nitrogen to such soils — Effect of nitrogenftus food 

 on the aspect of yoimg plants ; on potatoes — Empirical and rational 

 systems of agricidture. 



FPlOM the results of a series of most careful observa- 

 tions extending over a number of years made by 

 Bineau in different parts of France on the amount of 

 ammonia and nitric acid in rain water, it appears that 

 there fell annually upon the area of a hectare ( = 2i acres) 

 2Tkilogrannnes( = 51J lbs.) of ammonia( = 22kilo. = 481bs. 



u 



