130 AGRICULTURAL ENGINEERING 



be so broken down as to allow the soil particles to run to- 

 gether and form a compact mass. Soil in such a condition is 

 said to be water-tight. The air cannot enter a soil of this 

 kind, and an aerated soil is essential in furnishing favorable 

 conditions for plant growth. If too much water is applied 

 to the soil, it becomes water-logged and suffers for the lack 

 of air in the same way. 



Preparing Land for Irrigation. As irrigation water is 

 usually applied by the aid of gravity, great care should be 

 used in preparing the surface ground and the ditches and 

 small laterals necessary to convey the water over the fields. 

 The proper slope must be given to the surface to give an even 

 distribution of the water. For this reason one of the largest 

 items of expense involved in bringing land under irrigation is 

 the cost of preparing the land. Usually irrigable land is 

 covered with some sort of growth which must be removed. 

 It costs from $1.50 to $4 per acre to remove sage brush, which 

 is usually found on the land in the arid sections of the United 

 States. The land must be thoroughly gone over with graders 

 and other leveling machines and worked until the surface is 

 made a perfect plane. 



Dr. Elwood Meade states that the cost of preparing the 

 land for irrigation in the United States varies from $3 to $30 

 per acre. The following table shows the average cost of 

 preparing land for different methods of irrigation : 



Check method $ 3.60 



Flooding method 2.75 



Furrow method 3.50 



Basin method 4.50 



Methods of Applying Water. There are many methods 

 of applying water to irrigated crops, and nearly all are 

 practiced in the United States. The method to be used in 

 any particular case depends largely upon the nature of the 



