FERTILIZER PRACTICE 549 



4. It weakens the straw and causes lodging in grain. This 



is due to an extreme lengthening of the internodes, 

 and as the head fills the stem is no longer able to 

 support the increased weight. 



5. It lowers quality. This is especially noticeable in 



certain grains and fruits, as barley and peaches. 

 The shipping qualities of fruit and vegetables are 

 also impaired. 



6. It increases the percentage of nitrogen in the crop, 



particularly in the straw of cereals and in timothy 

 hay. 



7. It decreases resistance to disease. This is probably due 



to a change in the physiological resistance to disease 

 within the plant, and also to a thinning of the cell 

 wall, allowing a more ready infection from without. 



While certain plants, as the grasses, lettuce, radishes, 

 and the like, depend for their usefulness on plenty of 

 nitrogen, for the average crop it is generally better to 

 limit the amount of nitrogen so that growth may be 

 normal. This results in a better utilization of the nitro- 

 gen and in a marked reduction of the fertilizer cost for a 

 unit of crop growth. This is a vital factor in all fertil- 

 izer practice, and shows immediately whether fertilization 

 is or is not an economic success. 



467. Effects of phosphorus on plant growth. — It is 

 difficult to determine exactly the functions of phosphoric 

 acid in the economy of even the simplest plants. Neither 

 cell division nor the formation of fat and albumen go on 

 to a sufficient extent without it. Starch may be pro- 

 duced when it is lacking, but will not change to sugar. 

 As grain does not form without its presence, it very 

 probably is concerned in the production of nucleoproteid 



