HOW PLANTS FEED AND GROW 29 



POUNDS POUNDS 



Millet 275 Wheat 507 



Pigweeds and Russian thistles 322 Oats 614 



Sorghums 306 Sweet clover 709 



Corn 369 Rye 724 



Sugar beets 377 Canada field peas .... 800 



Potatoes 488 Alfalfa 1068 



From this table it is easy to understand why oats require a 

 moist climate, as compared with millet. Taking wheat as a 

 standard, the table shows that the sorghums require little more 

 than half as much water as wheat ; corn, three-quarters as much ; 

 oats and sweet clover, about one and one-half times as much ; 

 alfalfa, more than twice as much. Different varieties of the 

 same plant require different amounts of water. For example, a 

 drought-resistant corn from Mexico requires only three hundred 

 and nineteen pounds of water for a pound of dry matter, while 

 Iowa Silver Mine corn uses four hundred and twenty pounds. 

 Of all agricultural plants tested, alfalfa requires the most water. 

 Alfalfa, by reason of its deep-rooting habit, feeds through a 

 greater area than other plants, and is therefore among the last 

 to suffer. The large amount of water used by alfalfa explains 

 why crops that follow alfalfa, such as corn, often suffer for lack 

 of sufficient moisture. 



32. Plants on fertile soil use water economically. Plants 

 which grow in well-manured soils produce crops on less water 

 than plants growing on poor soil. This is because plants on 

 fertile soil grow rapidly, and manufacture a given amount of 

 plant material in less time than when growing in poor soil. In 

 poor soil plants manufacture little or nothing for long periods, 

 although the water passes through their bodies all of the time. 

 High fertility, therefore, means more rapid production and con- 

 sequently cheaper farming. Plants must be rushed at their work. 



33. How the plant gets rid of surplus water. To maintain 

 rapid, economical growth, a constant stream of water, carrying 

 the nutrients from the soil, must pass into the plant. Most of 

 the water passes through the plant and into the air as a vapor. 



