CHAPTER XI 



THE PLANT AS AFFECTED BY UNFAVOR- 

 ABLE FOOD SUPPLY 



WE saw that water is the most important constituent 

 of plant-food (62) and we have already considered the 

 plant as affected by water supply. But a proper supply 

 of the other essential food constituents is only second in 

 importance to that of water. 



EXCESSIVE FOOD 



248. Excess of most foods. Excessive food is not 

 the extreme that we have most to fear, since natural 

 soils are rarely excessively fertile, and we can make them 

 so only by costly methods. Indeed, nearly all of the 

 constituents of plant-food may be present in excess of 

 the requirements of plants without working harm. Nitro- 

 gen, however, which aside from water is the most potent 

 food constituent, must be used with some discretion. 



249. Excessive nitrogen stimulates growth at the ex- 

 pense of flowers, seed and fruit. In crops grown for these 

 parts, therefore, fertilizers rich in nitrogen must be used 

 with caution. Apple, pear and quince orchards lib- 

 erally manured with such fertilizers produce an ex- 

 cessive, over-succulent growth of the wood, that is sub- 

 ject to blight and winter injury and forms comparatively 

 few fruit buds. Grain under similar conditions forms 



144 



