NITROGEN IN AGRICULTURE. 305 



situated, were rich in nitrogen, and gave heavy crops of 

 wheat and other cereals ; but they gradually languished, 

 until the raising of wheat, a grain demanding much nitro- 

 gen, no longer proved remunerative, and its cultivation, to 

 a large extent, ceased. 



New-England soils, at the dawn of scientific agriculture 

 thirty years ago, were apparently in a fixed condition : fif- 

 teen or twenty bushels of corn could be got from an acre, 

 small crops of barley or oats, but no wheat in paying quan- 

 tities. The supply of nitrogen was at a minimum ; and it 

 probably varied but little from year to 3'^ear, unless on fields 

 which received more enlightened culture from owners than 

 was usual throughout the countr3\ 



These facts all tend towards one conclusion, — that the 

 spontaneous supply of nitrogen on soils physically well 

 adapted to grains and rich grasses is tolerably constant, and 

 is sufficient for the sustention, growth, and maturity of small 

 crops from year to year, without additions from outside 

 sources. Some lands, originally well supplied with nitrogen, 

 become sterile under repeated croppings with the cereals ; 

 but such are peculiar in physical characteristics, and not 

 well adapted to receive and retain manures of any kind. As 

 is well known, the tendency of all soils is towards exhaus- 

 tion, when drawn upon by successive crops of the noble grains 

 and grasses ; but this exhaustion seems to have a limit, so 

 far as it is due to loss of nitrogen. 



As gaseous nitrogen is rejected by plants, we must assume 

 that it reaches them through the nitric acid and ammonia 

 alwaj^s ptesent in the atmosphere. Every shower of rain, 

 every fall of snow or dew, brings with it to the land a 

 variable but large supply of these bodies ; and they are dif- 

 fused through the moist earth, and held for the use of vege- 

 tation. It is a very remarkable and significant fact, that the 

 amount of nitrogen supplied through the sources indicated 

 varies on different fields, often on the same farm, and under 

 similar meteorological conditions. This fact has not been 

 noticed by writers and experimenters, so far as my knowl- 

 edge extends. 



It appears clear, from the results of experiments at my farm, 

 that no two fields receive precisely the same amount of natural 

 nitrogenous products in a single season, or in a succession 



