70 



CORN 



Potassium is taken in largely as a nitrate, chloride, carbonate, sul- 

 phate and phosphate. In the assimilation of carbon dioxide the pro- 

 cess is facilitated by the presence of potassium. Any plant containing 

 a large percentage of carbohydrates usually shows a considerable 

 amount of potassium in the ash. The fact that wheat straw loses its 

 stiffness upon a soil which is so rich in nitrogen as to force the plant 

 along without sufficient potash, proves this. The glazed surface and 

 woody wall of the corn stalk are due to the strengthening power of 

 potash. 



(4) Calcium. Calcium, usually known as CaO, or lime, is neces- 

 sary to correct the acidity of soils which have been farmed contmu- 

 ously, and whose humus content has been almost exhausted. Al- 

 though of less importance in the actual development of plants, the 

 amount of lime in the ash of barley, oat, and wheat straw is generally 

 about seven per cent.* 



(5) Other Plant Foods. Sulphur enters into the composition of 

 the protein. Magnesia is found in the ash of seeds, especially in small 

 grains. Iron is an essential element of chlorophyll. Plants grown in 

 nutrient solutions, free from iron, have no green color. Although .sili- 

 con, sodium, and chlorine are present in the ash of plants, some author- 

 ities claim tliat they are unessential to the growth of plants. 



The following table gives the amount of the three chief elements 

 of plant food found in the principal farm crops by analyses. 



TABLE NO. IS 



SHOWING AMOUNT OF PLANT FOOD IN PRINCIPAL FARM CROPS. 



Amount 



Nitrogen 



Phosphorus 



Potassium 



Corn, grain . 

 Corn, stover . 

 Entire crop . . 

 Oats, grain . 

 Oat straw . . 

 Entire crop . . 

 Wheat, grain 

 Wheat straw 

 Entire crop . 

 Timothy hay 

 Clover hay . . 

 Cnwpea hay . 

 Alfplfa hay . . 



100 bushels 

 6 tons 



75 bushels 

 2 tons 



40 bushels 

 2 tons 



2 tons 



3 tons 

 3 ions 

 8 tons 



19 pounds 

 52 

 71 

 9 

 40 

 49 

 11 

 34 

 45 

 47 

 90 

 95 

 192 



The table showing the amount of different elements taken from the 

 soil by the principal crops is taken from circular No. 68 of the Illmois 

 Experiment Station. 



COLLATERAL READING: 



Effect of Fungicides upon Germination, 



Kansas Bulletin No. 41. 

 Water Requirements of Corn. 

 Utah Bulletin No. 86. 



^"Agricultural Botany," Percival. 



