Effective agronomic practices are essential components of irrigated systems. Management of the soil fertility, cropping selection and rotation, and pest control may make as much incremental difference in yield as the irrigation water itself. Irrigation implies drainage, soil reclamation, and erosion control. When any of these factors are ignored through either a lack of understanding or planning, agricultural productivity will decline. History is absolutely certain on this point.
Irrigated agriculture faces a number of difficult problems in the future.
One of the major concerns is the generally poor efficiency with which water resources have been used for irrigation. A relatively safe estimate is that 40 percent or more of the water diverted for irrigation is wasted at the farm level through either deep percolation or surface runoff. These losses may not be lost when one views water use in the regional context, since return flows become part of the usable resource elsewhere. However, these losses often represent foregone opportunities for water because they delay the arrival of water at downstream diversions and because they almost universally produce poorer quality water. One of the more evident problems in the future is the growth of alternative demands for water such as urban and industrial needs.