SOIL NITROGEN 19 



known. The scientific explanation of their value has now become common 

 knowledge. 



Winogradsky in 1895 reported his discovery of a microorganism in the soil 

 which could use air nitrogen without the roots of clovers for living quarters. 

 Beijerinck in 1902 described another kind of bacteria yet more capable of com- 

 bining air nitrogen into nitrogen compounds of use to plants. Winogradsky, 

 in Soil Science for July 1935, offers a method for their study which can be 

 related to natural soil conditions. 



Nitrogen fertilizers in 1889 were the natural deposit of nitrate of soda and 

 by-products like ammonium sulfate from gas works and animal refuse from 

 abattoirs. Chemical synthesis of nitrogen from the air with oxygen also from 

 the air had long been possible in the laboratory but was impracticable on a 

 commercial scale. Development of water power and electrical energy in 

 Norway enabled Dr. Eyde to report the successful commercial development 

 of synthetic nitric acid and nitrate of lime at the International Congress of 

 Applied Chemistry in New York in 1912. At the same meeting, Dr. Haber 

 demonstrated his synthesis of ammonia from air nitrogen and hydrogen. 

 Several years earlier, Ostwald had developed the catalytic oxidation of am- 

 monia to nitric acid. From 1914 to 1918, these two inventions of Haber and 

 Ostwald enabled Germany to make ammunition from an inexhaustible source 

 of raw materials. 



Since the World War, every nation seeks to provide itself with means to 

 synthesize nitrogen, hydrogen, and oxygen into ammonia and nitrates. A 

 wholly new set of conditions, both scientific and economic, now surrounds the 

 use of fertilizers. Fertilizer experiments must be rearranged to meet new 

 problems. 



SUMMARY 



For 12 years, continuous production of nonlegume crops has been compared 

 with the alternation of a legume with a nonlegume crop. 



Continuous absence of nitrogen fertilizers has been compared with the al- 

 ternation of applied nitrogen with residual nitrogen. 



Nitrogen applied to legume crops produced no practical gain with clovers, 

 about 7 percent increase with soybeans, and between 8 and 9 percent increase 

 with mixed oats and peas. Nitrogen applied to six nonlegume crops increased 

 their total product 41 percent. 



Residual nitrogen and absence of nitrogen produced virtually equal yields 

 on the legume subplots. Residual nitrogen produced 10 percent more dry 

 matter on the nonlegume subplots. 



On plots which received nitrogen it was applied in 7 years out of 12, to 

 the total amount of 315 pounds per acre. On these plots, alternation of legume 

 crops with nonlegume crops produced in 11 harvests a total of 41,580 pounds 

 per acre of dry matter containing 750.1 pounds of nitrogen; continuous non- 

 legume crops produced 46,640 pounds of dry matter and 493.6 pounds of ni- 

 trogen. The nonlegume subplots produced 12 percent more dry matter, but 

 34 percent less nitrogen than was produced by the legume subplots. 



On the plots which did not receive nitrogen fertilizers, alternation of legume 

 crops with nonlegume crops produced 40,120 pounds per acre of dry matter 

 containing 741.7 pounds of nitrogen; continuous nonlegume crops produced 

 35,590 pounds of dry matter and 356.9 pounds of nitrogen. The nonlegume 

 subplots produced 11 percent less dry matter which contained 52 percent less 



