378 THE IRRIGATION AGE. 



or sprinkling, and the latter is probably out of the question because 

 of cost of outfit and attendance. 



(3) The character of the soil. Soils naturally very open or loose, 

 or market-garden soils rendered very loose by the constant and deep 

 working in of coarse manures, favor such rapid percolation that even 

 distribution through the soil mass can be had only by covering the 

 surface rapidly with a uniform sheet of water. Under such condi- 

 tions, also, flooding and sprinkling are the only practicable alterna- 

 tives. The fact that sprinkling is not practiced to any extent in 

 regions where much irrigation 'is done invites the conclusion that 

 some form of flooding is better. On the other hand, for soils which 

 take water slowly and distribute it well, both laterally and vertically, 

 the furrow system, distributing water between long rows of plants, is 

 best for plants which are profitably grown in rows, and on land of a 

 grade which does not force too rapid flow of water. 



(4) The labor requirement. The largest area can be evenly 

 moistened with least labor by the contour check system and by the 

 furrow system. Each is superior to all others in this respect for the 

 conditions of land and crop to which it is adopted. The labor require- 

 ment in preparation of the ground has been so reduced by improved 

 grading and leveling devices and by using permanent levees which 

 allow all the ground to be cropped instead of counting the levees 

 waste land, that the first cost of putting the land in shape for flooding 

 in contour checks is but a slight addition to the grading necessary 

 to remove the knolls and sags which is necessary in preparation for 

 the furrow system. 



(5) Ease of cultivation after irrigation. The desirability of stir- 

 ring the soil surface after irrigation has already been mentioned in 

 discussing methods of applying water. It is a means of checking 

 evaporation and consequent lack of moisture, but it is more than 

 that. The effect of irrigation is to draw the soil particles together, 

 and if it be a soil containing much clay there is compacting followed 

 by cracking as drying proceeds. In the old practice this condition was 

 taken as a demand for more water, and another irrigation was given, 

 which merely aggravated the trouble and plants came to distress. 

 More water was used than necessary for good growth, and still thrift 

 was not secured. The remedy is cultivation as soon after irrigation 

 as the soil is in condition to break readily and become mellow and 

 friable. Except, perhaps, where a mulch is used, cultivation is essen- 

 tial to the best soil condition, and consequently to the most satisfactory 

 growth of the plant. It follows, then, that methods of irrigation which 

 facilitate subsequent cultivation are to be preferred, wherever the 

 ground slope and the character of the soil favor them. Of all methods 

 that of irrigation by furrows between straight rows of considerable 



