FERTILIZERS 



chiefly in combination with other elements in the form of 

 vegetable matter. As soon as the vegetable matter in the 

 soil decomposes (rots), the nitrogen is made soluble or goes 

 off into the air as gas, so that it is very easily lost. A soil 

 that is lacking in vegetable matter is likely to be lacking 

 in nitrogen. A good supply of nitrogen in the soil stim- 

 ulates the growth of plants. A dark green color of the 

 growing plants generally indicates plenty of nitrogen. 

 When the foliage turns yellow before it is ripe, there is 

 usually a scarcity of nitrogen. Nitrogen is an essential 

 element of protein. The amount in normal soils varies from 

 2,000 lbs. to 10,000 lbs. in the upper seven inches. 



Phosphorus is needed by all plants. It is needed es- 

 pecially in crops like grain and corn that mature seeds. 

 The presence of plenty of phosphorus in the soil aids plants 

 in the production of seed. The kernels of wheat or rye 

 or corn are likely to be plumper and heavier where there is 

 a good supply of phosphorus. A lack of suflftcient phos- 

 phorus in the soil results in a smaller yield of grain, and the 

 grain produced is not so good in quality. Selling seeds, 

 such as wheat, barley, rye, or corn from the farm removes 

 from the farm comparatively large amounts of phosphorus. 

 The amount of phosphorus in normal soils varies from 1,000 

 lbs. to 2,000 lbs. per acre. When one considers the compar- 

 atively small amount of this element in the soil, and the 

 amounts removed by ordinary crops, as shown in the fol- 

 lowing table, one is impressed with the need of adding to 

 the supply in the soil before it gets too low. 



Approximate Amount of Fertility Removed by Crops. 



3^ 



