Using Halophytes to Mitigate Salinity Stress On Watermelons.

Fluctuations in rainfall, increased drought stress, limited water availability, and low-quality irrigation water are major concerns for agricultural producers.  Low-quality irrigation water and drought increase salinity in soils, which results in yield reductions of salt-sensitive crops such as watermelon.  The objectives of this project were to evaluate several halophytes to use as companion crops with watermelons and assess the effectiveness of these halophytes in mitigating salt stress in a field setting. Six plant species were selected to be screened based on their potential economic value and ability to accumulate salt.  Species selected for screening were four-wing saltbush (Atriplex halimus), barley (Hordeum vulgare), garden orache (Atriplex hortensis), purslane (Portulaca oleracea), saltwort (Suaeda salsa) and wheat (Triticum aestivum). Two species were selected to use in the field experiment evaluating salinity mitigation in watermelon intercropping systems. Salinity treatments consisted of irrigation water applied at rates of 0, 3, and 6 dS m^-1 throughout the studies.  Each plant species was replicated 5 times within each treatment in a random complete block design.  Soil bulk electrical conductivity (EC) data for the initial halophyte evaluation showed that for both salinity treatments orache, barley, wheat, and four-wing saltbush had the lowest soil EC levels. Preliminary absolute growth data showed that at 3 dS m^-1, orache, purslane, and saltbush had the highest rates amongst plant species at 2.41, 0.83 and 0.44 cm/day, respectively.  At 6 dS m^-1, orache out-performed the other species with an average absolute growth rate of 2.33 cm/day, followed by purslane and saltbush at 0.69 and 0.31, respectively.  Growth data indicate that orache thrived at all salt levels, showing increased growth at higher salt levels when compared to the control. These preliminary results suggest wheat, barley, saltbush and garden orache may be suitable companion plants to watermelon in saline conditions.