Purslane (Portulaca oleracea L.): A halophytic crop for drainage water reuse systems

Abstract

Drainage water reuse systems have been proposed for the west side of the San Joaquin Valley of California in order to reduce the volumes of water requiring disposal. Implementation of this system requires development of a cropping system with successively higher salt tolerance. A major limitation is the need to identify alternate species that will be suitable as the final, most salt tolerant crop in the series. These crops must be productive when irrigated with waters that are typically high in sulfate salinity and may be contaminated with potentially toxic trace elements. This study was initiated to evaluate the interactive effects of sulfate salinity and selenium on biomass production and mineral content of purslane (Portulaca oleracea). Plants were grown in greenhouse sand cultures and irrigated four times daily. Treatments consisted of three salinity levels with electrical conductivities (EC_i) of 2.1, 15.2, and 28.5 dS m⁻¹, and two selenium levels, 0 and 2.3 mg L⁻¹. In the initial harvests, shoot dry matter was reduced by 15 to 30% at 15.2 dS m⁻¹ and by 80 to 90% at 28.5 dS m⁻¹. Regrowth after clipping above the first node was vigorous and biomass from plants irrigated with 15.2 dS m⁻¹ water was nearly double that from the 2 dS m⁻¹ treatment. Purslane appears to be an excellent candidate for inclusion in saline drainage water reuse systems. It is (i) highly tolerant of both chloride- and sulfate-dominated salinities, (ii) a moderate selenium accumulator in the sulfate-system, and (iii) a valuable, nutritive vegetable crop for human consumption and for livestock forage.