Plants as Affected by Insufficient Food. 153 



mal plant structure cannot be built up. An excess of 

 one food substance cannot compensate for the lack of 

 another, except in a few instances. 



251. Insufficient Food Dwarfs the Plant in all its 

 parts. A dwarfing of the size of the plant body may- 

 occur, however, without a corresponding dwarfing of the 

 seed product; hence plants may often bear their maxi- 

 mum amount of seed or fruit without attaining their 

 maximum dimensions. Plants grown for seed or fruit 

 are, therefore, less likely to be restricted in yield by in- 

 sufficient food than those grown for their leaves, stems, 

 roots or tubers. The cereals, for example, produce well 

 on land not sufficiently fertile to yield equally good 

 crops of tobacco, cabbage, celery, lettuce or potatoes. 

 But with a sufficient restriction of food, the seed product 

 will suffer diminution or be wholly cut off. 



252. Crop-Growing Tends to Reduce Plant Food in 

 the soil in proportion as the fertilizing components of 

 the crops are removed from the land and are not re- 

 turned to it, directly or in equivalent. Fortunately, 

 considerable plant food is constantly being liberated by 

 the disintegration and decay of rock or soil materials, 

 or is being deposited from the atmosphere in rain or 

 snow, so that it is impossible to exhaust the soil of 

 plant food, even with the most improvident culture. 

 But the cultivator should aim at the largest returns 

 from his soil, and these are impossible without restor- 

 ing certain materials that continued crop-removal in- 

 variably reduces below the limit of profitable yields. 



253. The Food Elements Most Likely to be Defi- 

 cient, when plants are properly s-applied with water, 



11 



