Part III.] Pond Fish Culture. 203 



population of our country is rapidly increasing, and men wise 

 in business calculations, including the railroad magnate, Mr. 

 J. J, Hill, tell us that within fifty years the population of the 

 United States will reach 200 million. This seems possible, as 

 the increase during the past ten years has been more than 

 16 million. 



Why so much concern about conservation and soil fertility? 

 By examining the above-mentioned reports further, we learn 

 that there is a great waste in soil fertility to the state and 

 country, partly due to natural causes, but largely to the im- 

 provident methods employed in connection with agricultural 

 pursuits. 



COST OF PRODUCTS MEASURED IN FERTILIZING MATERIALS. 



It costs to produce 20 bushels of wheat $5.79 worth of 

 fertilizer — nitrogen, phosphorus and potassium.* To produce 

 the ton of straw on which this wheat grew $3.66 worth of ferti- 

 lizer is used, or a total of $9.45 for the wheat and straw. To 

 produce 65 bushels of corn, a good acre yield, it costs in ferti- 

 lizer $9.38, and $9.32 to produce the 3000 pounds of stalks on 

 which the corn grew, or a total of $18.70 in fertilizer for what 

 might be taken from a single acre of ground in corn products. 

 Again, four tons of alfalfa removes from an acre of ground 

 13.75 pounds of phosphorus worth $1.10; 200.80 pounds of 

 potassium worth $12.09; and 85.44 pounds of calcium worth 

 42 cents, or a total of 300 pounds of fertilizer worth $13.19. 

 The removal of the phosphorus is most damaging as it is an 

 element rare even in good soils the world over, and should be 

 conserved in farm lands as it will be difficult and expensive 

 to replace when once exhausted. 



CROP ROTATION AND SOIL FERTILITY. 



The idea of crop rotation so much advertised and advised in 

 agricultural journals and societies is a good one. By this 

 means, through the agency of bacteria, nitrogen can be restored 

 to the fields ; but no amount of crop rotation will restore phos- 

 phorus. Once removed from the fields this element can be re- 

 turned to the soil only by some mechanical means, and the 

 same thing is true of potassium and other mineral matters. 

 The idea held by many persons that the growing of alfalfa on 

 ground enriches it is an erroneous one; while the growing of 

 alfalfa, clover, and other such plants, adds to the nitrogenous 

 compounds, it robs the soil of the very mineral elements that 

 constitute a good part of its crop-producing substances. 



SPECIAL VALUE OF FERTILIZERS. 



We are told that the wheat crop of 1909 — in round numbers 

 82 million bushels — took from Kansas fields 160 million pounds 

 of rich fertilizer which would cost over 26 million dollars if it 



* See Bulletin 169, page 76, Kansas Agricultural Experiment Station. 



