SOIL TEXTURE AND COMPOSITION 



89 



stone or lime. Calcium sulfate is often used to correct the ill 

 effect of black alkali. 



Magnesium — Magnesium differs from calcium and potassium 

 in that as the plant ripens it migrates to the seed. Magnesium 

 is essential in the production of chlorophyll. Hence, magnesium- 

 starved plants have an unhealthy color. Excessive amounts pro- 

 duce harmful effects which can be corrected by calcium. 



Iron — Plants do not possess their healthy green color v^^hen iron 

 is lacking. Although iron is essential for the production of 

 chlorophyll, yet it does not enter into its composition. Very small 

 quantities are needed by plants. All soils contain sufficient iron. 



Sulfur — Cabbage and root crops require more sulfur than do 

 other crops. It gives to garlic, horseradish, and onions their pe- 

 culiar taste and odor. These plants grown in soils containing 

 small quantities of sulfur are mild. Small quantities of sulfur 

 are essential to all plants as it enters into the production of the 

 proteins. Probably most soils contain sufficient sulfur for plant 

 needs, yet the addition of sulfur to a soil is often accompanied by 

 increased yields* This may be due to sulfur bacteria changing the 

 sulfur to sulfuric acid which liberates phosphorus or other plant 

 nutrients in the soil. 



We have seen that the three elements which are used by the 

 plant from the soil in largest quantities are nitrogen, phosphorus, 

 and potassium. The money value and quantity of these required 

 by the wheat, potato, and sugar-beet crops are given below. 



Product 





Pounds 



Market Value 



Total 







Nitro- 



Phos- 



Potas- 



Nitro' 



Phos- 



Potas- 



Value 



Kind 



Amount 





















gen 



phorus 



sium 



gen 



phorus 



sium 





Wheat 



50 bu. 



71 



12 



13 



$10.65 



$ .36 



$ .78 



$11.79 



Wheat-straw 



2.5 tons 



H 



4 



45 



3-75 



.12 



2.70 



6.57 



Wheat crop 





96 



16 



58 



14.40 



.48 



3-48 



18.36 



Potatoes 



300 bu. 



100 



13 



90 



9-45 



'39 



5.40 



15.24 



Sugar-beets 



20 tons 



100 



18 



157 



15,00 



•54 



9.42 



24.96 



