ALFALFA YIELD RESPONSE TO GROUND-WATER AFTER TERMINATION OF IRRIGATION

In the absence of irrigation, water from a water table below the root zone can sometimes sustain crop growth. This study was conducted to determine whether alfalfa grown without irrigation, but in the presence of a water table below the root zone, can give normal yields. Three irrigation treatments were applied: irrigating during the first two growth cycles, irrigating during the first three growth cycles, and no irrigation restrictions for the four growth cycles of the irrigation season. Water-table depths midway between parallel tile drains were evaluated. Yields from the midway position between drains were compared with yields nearer the drains. The influence of occurrence/nonoccurrence of irrigation on yield was also tested by regression analysis. Water tables tended to be deeper in the absence of irrigation but differences were small among the three treatments. Yield was dependent on the occurrence of irrigation but not on water-table depth. Most important, nonirrigation caused an 80% drop in yield.