It is likely that better managers soil test and that their soil tests are higher than the average. Home and garden samples could not be separated from agricultural samples. Since these average considerably higher than agricultural samples, they contribute to an upward bias. The amount of water used for irrigation in arid and semiarid regions reflects the efficiency of application. Modern irrigation systems, such as low-pressure sprinkler systems and surface and subsurface drip systems, have allowed producers to significantly reduce water application rates.
Artificial drainage is used to increase aeration to the roots of growing plants.
Conflicts have arisen over a broad array of related policy questions, such as clearing and draining the Mississippi Delta, draining prairie potholes and other wetlands, managing return flow from irrigated land, and controlling water levels on coastal lands. The data presented here are for1975-1985. It is likely that the number of cropland acres with artificial drainage systems has grown more slowly since 1985, because a number of major federal policy initiatives directed toward reducing inappropriate drainage have been implemented since that time.