FEASIBILITY OF CYCLIC REUSE OF SALINE DRAINAGE IN A TOMATO COTTON ROTATION

Use of saline drainage water for crop irrigation has been proposed as a strategy to reduce drainage volume and conserve good quality water. Over a 6-yr period, two cyclic drainage-water reuse practices were tes ted in a 3-yr rotation of processing tomato (Lycopersicon esculentum L .) and cotton (Gossypium hirsutum L.). In both practices, drainage wat er (EC(i) = 7.4 dS m(-1) and 0.74 mmol L(-1) B) was applied to process ing tomato after first bloom to take advantage of salt-induced enhance ment of fruit quality and increased crop salt tolerance at later devel opmental stages. In one practice, drainage water was also applied to t he following cotton crop after thinning. Nonsaline water was used for irrigation at all other times and throughout for the control. When sal ine water was applied once every 3 yr, yields of both crops were unaff ected. Tomato yields were generally lowest when saline water was appli ed 2 out of 3 yr, but saline water improved tomato fruit quality by in creasing (o)Brix in most years. Changes in soil chemical and physical quality may limit long-term reuse. Both B and salts accumulated in the soil over time, particularly at depth (60-140 cm), whereas Se was mor e readily leached and showed greater fluctuations in the rootzone with irrigation treatment. Calculations using reclamation formulae estimat ed that for low B drainage water, the amount of drainage wager used ex ceeded that of nonsaline water needed to return soil EC(e) to control levels, resulting in significant water savings. For high B drainage wa ter, more than twice the amount of nonsaline water was needed to fully reclaim the profile than was saved by reuse. However, moderately B-to lerant crops could be successfully grown during the reclamation period , making cyclic reuse for at least 6 yr an attractive option for growe rs facing limited supplies of nonsaline water supplies, or as a means to reduce effluent volumes.