326 CROP ROTATION 



actually be increased by the turning under of the legume is certain 

 from field experiments. 



The Dominion of Canada Experiment Stations grew mammoth 

 clover for two successive seasons on a soil very low in nitrogen. 

 The two cuttings of mammoth clover with all the residues were 

 turned under each year with the result that the soil gained as an 

 average 177 pounds per acre of total nitrogen which is the quantity 

 ot nitrogen found in three 40-bushel crops of wheat, provided the 

 straw was returned to the soil, as two tons of this contains 20 

 pounds of nitrogen. On the other hand, work on the soil of the 

 Utah Nephi Experiment Farm, with a rotation of wheat and peas 

 where the peas were plowed under, showed a gain in total nitrogen 

 of 240 pounds in four years. That is, in addition to furnishing the 

 small quantity of nitrogen required by the wheat crop, the peas 

 had added to the soil an average of (30 pounds of nitrogen per year. 



The second method of maintaining the nitrogen and organic 

 matter of the soil the combined rotation and livestock method- 

 is the more practical, and if systematically practised will not only 

 maintain the nitrogen of the soil but will prove of great economic 

 value to the individual following it. For it consists of a rotation 

 in which the legume plays a prominent part. The legume to be 

 fed and all the manure returned to the soil, which would mean the 

 selling from the farm of the hay crop in the form of butter, milk or 

 beef which carries from the soil only a fraction of the nitrogen 

 stored up by the legume. Moreover, it brings for the producer 

 much greater returns than does the system in which the legume is 

 plowed under. 



It must, however, be remembered in this system that only three- 

 fourths of the total nitrogen of the feed is recovered in the dung 

 and urine. So that in place of three tons of alfalfa adding 150 

 pounds of nitrogen to the soil from the air, it would add only 120 

 pounds, and this is where all of the liquid and solid excrements are 

 collected and returned to the soil. But where the alfalfa is to be 

 fed and the manure returned to the soil, the legume can occupy 

 a much longer period in the rotation and that with greater economy 

 than where the legume is to be plowed under directly. 



Hence, we find that if these principles which have been estab- 

 lished for soils even low in nitrogen be systematically applied to 

 the soil, it will result in greater revenue from an increased live- 

 stock industry and will maintain the soil rich in nitrogen and 

 organic matter in place of depleting it of its stored-up nitrogen, 

 as is so often the case with the present methods. 



REFERENCES. 



Hopkins: Soil Fertility and Permanent Agriculture. 



Crravfs, Stewart and Hirst: Influence of Crop, Season and Water on the Bac- 

 terial Activities of the Soil, Jour. Agr. Research, ix, 293-341. 



