Corrugation irrigation is well adapted for the irrigation of medium- and heavy-textured soils. If fields have a tendency to bake, they are difficult to irrigate by flood methods. Flooding causes the soils to puddle and run together, which results in a hard crust after the surface dries. The crusting may retard plant growth. Applying water through corrugations will correct this con- dition, since the water “subs” across under the surface between the corru- gations and does not puddle the soil. Even with corrugations, heavy soils are difficult to irrigate because they take water very slowly.
Silt loams and fine sandy loams, the easiest soils to irrigate, respond very well to irrigation by the corrugation method because the movement of the water is fairly uniform both sideways and downward. Corrugation irrigation is not recommended for soils that are very sandy. These soils take water rapidly, and the movement of water is mainly down- ward. Sideways movement between the corrugations is slow and much water may be wasted below the crop root zone before the area between corru- gations is irrigated. Also, the corrugation method is not recommended for soils having high concentrations of alkali salts. Flooding methods are better. The “subbing” action of corrugations will tend to take the salts into solution and move them toward the surface, causing even heavier concentrations of these salts.
The corrugation method is well adapted for irrigating land that is steep or irregular. Often, new land may be cleared and put into production the first year. The cost of leveling and the delay in time before planting may be largely eliminated. But. your fields will produce more with less labor if they are graded to smooth out the high and low areas. On slopes steeper than 5 percent, float leveling alone may be enough. On land under 5 percent, you may need to use a scraper to grade the more irregular areas before using the float leveler. W hen the field is properly smoothed, crops are not drowned out in the low areas while slightly higher areas are left dry. The corrugations carry the water uniformly to all parts of the field.
Corrugation irrigation may be used to irrigate most close-growing non- cultivated crops. Lsually. the corrugations are made, as the final tillage operation, after the field has been seeded. Forage crops such as alfalfa, clover, and grasses are watered by this method. Wheat, oats, and barley are commonly irrigated with corrugations. This is also a practical and safe method for irrigating your fields before seeding a crop. Corrugations ma\ be used to get new pasture seedings started. After the plant- are large enough to shade the ground and the root system is well enough along to keep the soil from washing, some method of flooding can be used to appt) the irrigation water.