THE PEINCIPLES OF FERTILIZER PRACTICE 475 



tendency to lodge, wMch is likely to occur especially with, 

 oats if too much available nitrogen is present. In certain 

 cases, phosphoric acid decidedly improves the quality of the 

 crop. This has been recognized in the handling of pastures 

 in England and France. The effect on vegetables is also 

 marked. Phosphorus is also known to increase the resistance 

 of some plants to disease, due possibly to a more normal cell 

 development. In this respect phosphoric acid counteracts the 

 influence of a heavy nitrogen ration. 



Excessive quantities of phosphoric acid ordinarily have no 

 bad eifect, as phosphorus does not stimulate any part unduly, 

 nor does it lead to a development which is detrimental. The 

 lack of phosphoric acid is not apparent in the color of the 

 plants as in the case of nitrogen, and as a consequence phos- 

 phoric acid starvation may occur without any suspicion there- 

 of being entertained by the farmer. 



One of the most important phases to be noted from this 

 comparison of the effects of nitrogen and phosphorus is the 

 balancing powers of the latter on the unfavorable influences 

 generated by the presence of an undue quantity of the former. 

 The possible detrimental effects of too much nitrogen have 

 already been noted. This relationship between the phosphorus 

 and nitrogen in plant nutrition is very important in fertiUzer 

 practice, since normal fertilizer stimulation generally results 

 in the most economical gains. 



267. Eflfects of potassium on plant growth. — The pres- 

 ence of plenty of available potash in the soil has much to do 

 with the general tone and vigor of the plant. By increasing 

 resistance to certain diseases it tends to counteract the ill 

 effects of too much nitrogen, while in delaying maturity it 

 works against the ripening influences of phosphoric acid. In 

 a general way, it exerts a balancing effect on both nitrogen 

 and phosphate fertilizer materials, and consequently is espe- 

 cially important in a mixed fertilizer, if the potash of the 

 soil is lacking or unavailable. 



