550 SOILS: PROPERTIES AND MANAGEMENT 



materials. Its close relationship to cell division may 

 account for its presence in seeds. Its general effects on 

 plant growth may be listed as follows : 



1. Phosphorus hastens maturity by its effect on rate of 



ripening. This makes phosphorus especially valu- 

 able in wet years, and in cold climates where the 

 season is short. 



2. It increases root development, especially of lateral and 



fibrous rootlets. This renders it valuable with 

 such soils as do not encourage root extension and 

 to such crops as naturally have a restricted root 

 development. Phosphorus is therefore valuable in 

 fall-sown crops, in years of drought, and for farm- 

 ing on arid land. 



3. It decreases the ratio of straw to grain by hastening the 



filling of the grain and by promoting maturity. 



4. It strengthens the straw, due to its balancing effect on 



the nitrogen. 



5. It 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. 



6. It increases percentage of phosphorus in the crop. 



With cereals this is particularly noticeable in the 

 straw. 



7. It increases resistance to disease, due probably to 



more normal cell development. 



Excessive phosphorus ordinarily has no bad effect, 

 as it does not stimulate any part excessively as does ni- 

 trogen, nor does it lead to a development which is detri- 

 mental. Its lack is not quickly apparent, as in the case 



