CORN GROWTH AND FEEDING 39 



grown frequently enough to insure a sufficient supply 

 of nitrogen for the development of the corn crop. 



The corn plant needs an abundance of the three 

 important ingredients of all fertilizers— nitrogen, phos- 

 phorus and potash. The nitrogen develops a large 

 growth of stalks, the phosphorus and potash are espe- 

 cially necessary in the growth of the seed. If any one 

 of these three elements is lacking, the result is a 

 dwarfed plant and small yreld. The most important 

 element, because it is most easily lost and is most ex- 

 pensive to buy in the form of commercial fertilizers, is 

 nitrogen. Most of the prairie soils have an abundant 

 supply of nitrogen. However, by continued cropping 

 the store of available nitrogen is used up and the effect 

 is easily seen in the growth of the plants on such 

 exhausted soils. 



For instance, at the Illinois experiment station 

 one-half acre has grown twenty-four successive crops 

 of corn without the aid of commercial fertilizers or 

 any kind of manure or special soil treatment. The 

 result has been a gradual decrease in yield. By com- 

 paring the growth of the plants on this half acre with 

 plants grown on rotated and manured fields, a very 

 great difference can be seen at any time during the 

 life of the plant. In the first place the young plants 

 are not thrifty. They do not start off vigorously. 

 Corn planted at the same time on well-fertilized plats 

 comes up two weeks earlier. The plants do not have 

 the dark green, healthy color of plants grown in soils 

 rich in nitrogen, and the leaves are a plain green 

 streaked with yellow. The stalks never eq".al in size 

 those of the same variety grown on rich soils. They 

 are weak, spindling, and have a dwarfed appearance 

 as though the climate had been unfavorable to their 

 development. During dry seasons the leaves curl and 

 the plant seems to suffer excessively from the lack of 



