90 PRODUCTIVE FARMING 



loss in seasons when certain crops are failures. The other 

 crops grown on the fields of the farm may not fail. 



Chief Needs of Rotations. The needs of rotation are 

 fairly well understood by most farmers. There is greatest 

 need when crops are suffering from particular weeds, bad 

 insect pests or diseases, or when the soil is becoming exhaust- 

 ed. However, rotation of crops should always be practised. 



EXERCISE. One Benefit of Rotation of Crops. Have 

 students dig out a few plants of different kinds of crops, 

 such as clover and timothy. They should study the root 

 systems and compare the deep-feeding roots with the shallow- 

 feeding ones. Shallow roots use the surface soil; deep roots, 

 such as clover, will bring up food from the subsoil. This 

 will help to make plain one value of rotation of crops. 



Bare Fallow. It is now considered bad practice to allow 

 ground to remain bare for any great length of time between 

 one crop and the next. It is sometimes a good plan to do this 

 for a few weeks providing the soil is kept pulverized on top 

 by the use of a harrow once a week or soon after each rain. 

 This practice of bare fallowing will cause the sprouting of 

 weed seeds and the harrow teeth will kill the young sprouts. 

 The soil moisture is also saved by the mulch of fine soil on 

 top of the field. 



Catch Crops. In place of fallowing has come the use of 

 catch crops. In this method the ground is kept covered with 

 a growing crop of some kind as much of the year as possible. 

 For example, after a grain crop has been removed, a crop of 

 cow peas, soy beans, millet, sorghum, or some other quick- 

 growing crop is seeded. Crimson clover (Fig. 48) and winter 

 vetch are often mixed with winter grain and sown in the 

 cornfield in July, so they will be ready to occupy the field 

 as soon as the crop is taken off. These three plants all 

 live through the winter. This winter cover crop is also used 

 after removing other crops such as early potatoes. 



How They Help the Farmer. Catch crops or cover crops 

 may be useful in several ways: 



