I,IME, GYPSUM AND GREEN MANURES IO9 



tent what crops to select. Green manure crops may be classified 

 as leguminous and non-leguminous. 



1, The leguminous green manure crops are those that have the 

 power of securing nitrogen from the air and are represented in 

 the clovers, cowpea, soy bean, alfalfa, vetches, velvet bean, 

 Canada field pea, etc. 



2. The non-leguminous green manure crops are those that 

 draw on the soil entirely for their supply of food, and rape, rye, 

 oats, buckwheat and mustard are examples of this class. 



Of the leguminous crops the red clover is the most popular in 

 the North and the cowpea and clovers in the South. Crimson 

 clover and alfalfa are also popular. The vetches and soy beans 

 are not used so much as the other mentioned legumes. 



Rye is the most common non-leguminous crop and is often 

 pastured in the fall or early winter. 



Leguminous Crops are to be Preferred. — The leguminous crops 

 are better than the non-leguminous because they can secure 

 nitrogen from the air and increase the soil supply of this con- 

 stituent. They also return more nitrogen to the soil when plowed 

 under. The non-leguminous plants simply draw on the soil 

 for food and when plowed under only add non-nitrogenous matter. 

 The principal benefit derived from the non-leguminous plants is 

 to save the loss of soluble plant food when a legume cantiot be 

 selected. The non-leguminous plants are more expensive to 

 grow because they require a supply of nitrogen and generally of 

 phosphoric acid and potash to insure good growth. The legumes 

 only require potash and phosphoric acid and sometimes only 

 phosphoric acid. So it is evident that rye, oats, rape, mustard, 

 etc., cannot take the place of the legumes in supplying green 

 manure as they cost too much to grow and do not return as much 

 fertility to the soil.* 



The Best Time to Plow Under a Green Manure. — Crops used for 

 green manuring should be plowed under before they become dry. 

 When they are plowed under while green and fresh they are more 

 readily decayed and prevent the loss of water somewhat from 

 light soils. Dry crops plowed under interfere with the use of 

 water from the subsoil and on light sandy soils may lower the 



