ECONOMIC SOLUTIONS 109 



to the bushel and for the sixteen-year period an average 

 of 46.7 bushels averaging 61.3 pounds per bushel. A 

 four years' rotation was employed. A light applica- 

 tion of barnyard manure was made once in each rota- 

 tion. No artificial fertilizers were used. 



So great a physicist as Sir William Crookes feared 

 that there was danger that the nitrogen of the soil might 

 be too scant for producing permanently sufficient wheat 

 crops. But through the discoveries of later investi- 

 gators we have learned that by means of the life of bac- 

 teria on the roots of clover, alfalfa, and all legumes, 

 nitrogen is taken directly from the air and prepared for 

 the use of other plants. There are only three factors in 

 depletion of fertility the loss of humus ; the decrease 

 of either of three inorganic elements, nitrogen, potash, 

 and phosphorus ; and deficiency of bacteria. All three 

 factors are easily controlled; the presence of any one 

 is most serious. On our prairies, humus, so abundant 

 in the virgin sod, is being lost so rapidly that the spring 

 winds blow away the soil, leaving the seed exposed. 

 The rotation of two crops and fallow must be replaced 

 by a rotation including grass or clover. " Experiment? 

 in Minnesota have shown that out of 170 Ibs. of nitro- 

 gen lost from virgin soil in a year only 27^ were 

 absorbed by the crop and 132^ were purely and simply 

 lost. The only means known whereby such loss can be 

 prevented is to alternate the raising of wheat with 

 crops of vegetables and of forage." Dr. Frank T. 

 Shutt. of the Dominion Experimental Farm, by means 

 of analyses which rank among the most thorough-going 

 ever made on this continent, has shown that there is 

 only nitrogen enough in the best soils of Canada for 

 150 crops of cereals, but over each acre floats in the air 



