IRRIGATION OF CEREALS 243 



By this method, the rows become checks to the descend- 

 ing water, and washing or unnecessarily rapid flooding 

 of the land is prevented. 



154. Cultivation of wheat. As explained in Chapter 

 IV, cultivation, properly performed, may largely take the 

 place of irrigation. On clayey soils there is a tendency 

 for a crust to form after each irrigation, which should be 

 broken to prevent serious injury to the plants. The present 

 system of planting grains hi rows very near each other 

 makes it difficult and probably unprofitable to give such 

 crops inter-row culture. However, wheat fields may 

 safely be cultivated while the plants are young from 8 

 to 12 inches high by harrowing with an ordinary spike- 

 tooth harrow with the teeth set backward, so that few 

 plants will be torn out. The corrugated roller is some- 

 times used to break the crust, but the harrow is probably 

 better, since it does not compress the soil. As the grain 

 becomes older it shades the ground very completely, and, 

 consequently, baking of the soil is not so common later 

 in the season. 



155. Method of irrigating wheat. Water may be 

 applied to wheat by any of the standard methods of irri- 

 gation. In the beginning of American irrigation, flooding 

 was almost the only method employed. Only gradually, 

 to meet compelling conditions, was the furrow method 

 thought out and adopted and, even today, flooding is the 

 most general method of irrigating wheat and other small 

 grains. The flooding of grain is accomplished ordinarily 

 by the field-ditch method. From the main supply ditch, 

 smaller ditches, often following the high lines or ridges, 

 are taken out to the field. From these again, small tem- 

 porary field ditches or mere furrows are made, from which 

 the water overflows to cover the land. Occasionally, but 



