FERTILIZER PRACTICE 551 



of nitrogen, and as a consequence phosphorus starvation 

 may occur without any suspicion thereof being enter- 

 tained 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 in- 

 fluences generated by the presence of an undue quantity 

 of the former. This is a vital factor in fertilizer practice, 

 since normal fertilizer stimulation always results in the 

 most economic gains. Such a normal increase is obtained 

 only when the plant functions of the several fertilizer 

 constituents are in proper accord. 



468. Effects of potassium on plant growth. — The 

 effects of potash are more localized than those of nitrogen 

 and phosphorus. Potash is essential to starch formation, 

 either in photosynthesis or in translocation, and is a 

 necessary component of chlorophyll. It is important 

 in grain formation, giving plump, heavy kernels. In 

 general it tends to impart tone and vigor to a plant. In 

 increasing resistance to disease 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 necessary in a mixed fertilizer, es- 

 pecially if the potash of the soil is lacking or unavail- 

 able. As with phosphorus, it may be present in large 

 quantities in the soil and yet exert no harmful effect on 

 the crop. 



469. Law of the minimum. — In connection with the 

 obvious importance of utilizing, for any particular soil 

 and crop, a fertilizer well balanced as to the three primary 

 elements, two queries naturally arise. These are: 



