MANURES AND FERTILIZING MATERIALS. 73 



ordinary crops. Soils which are dark or black in color 

 usually contain considerable organic matter and do not 

 need much nitrogen. Some soils are deficient in lime 

 and are sour or acid. To make a sour soil sweet, re- 

 quires the addition of lime. 



Effects of Fertilizer Ingredients. The ingredient 

 nitrogen tends to produce growth. If plants give a 



COWPEAS. 

 i, without fertilizer; 2, with fertilizer. 



rank growth it is generally due to an excess of nitro- 

 gen. Too little growth indicates a lack of nitrogen. 

 Phosphoric acid helps to form the grain of plants. A 

 deficiency of phosphoric acid results in light weight 

 grains, with such crops as corn, oats, wheat, barley 

 and rice. Phosphoric acid also tends to hasten ma- 

 turity in plants. Potash has a tendency to give firm- 

 ness to fruit and it enables the truck farmer to raise 



