AGRICULTURAL ENGINEERING 269 



Uses of irrigation are to furnish moisture, and some- 

 times plant food for growing crops, and it is sometimes used 

 to wash out of the soil undesirable salts (called alkali) 

 occasionally found in large enough quantities in soils to 

 injure plants. By applying large quantities of water, it 

 dissolves these salts, and if the soil is tiled or has a porous 

 subsoil, they are carried away and the soil will become 

 productive. 



Advantages of irrigation are a sure supply of moisture, 

 which is not always the case when farmers depend on rain- 

 fall. Water may be applied just when it is needed, and in 

 just the amounts needed. In such sections farmers are 

 very seldom bothered by rain when haying or harvesting. 

 The disadvantages are the cost of the water and ditches, 

 the labor of applying the water, and the bother of the 

 ditches in cultivating. 

 Questions: 



1 What is irrigation? What experience have you had with 

 irrigation? 



2. What are some of the sources of water for irrigation? 



3. Describe two or more ways by which irrigation water may 

 be applied to the soil. 



Arithmetic: 



1. How many cubic yards of earth would be moved in digging 

 a ditch 3 ft. deep and 3 ft. wide, 80 rods long? How much would it 

 cost at 15c. per yard? 



2. How many acres of land in a field 400 ft. square? How many 

 feet of furrows or small lateral ditches would be needed to irrigate 

 such a iield, assuming there was a main ditch along one side and that 

 the furrows were 15 ft. apart? 



FARM MACHINERT 



Machinery for doing farm work has been improved 

 wonderfully in the past half century. In fact, there is no 

 other part of the business of agriculture that has improved 

 so much as the machinery used. It is only a very short 

 time ago when plows were very crude, and crops were 

 planted, harvested and threshed by hand. The people of 

 the world owe much to the men who have given their time 

 and energy to the improvement of farm machinery. The 

 benefit has been equally valuable to people living in cities 

 as well as to farmers. When farm crops were produced 

 largely by hand labor, one man could handle only a very 



