WATER REQUIREMENTS FOR CULTIVATING SALICORNIA-BIGELOVII TORR WITH SEAWATER ON SAND IN A COASTAL DESERT ENVIRONMENT

The forage and oilseed halophyte, Salicornia bigelovii Torr., was grow n in gravity-drained lysimeters set in open plots of the same crop ove r two seasons in a coastal desert environment in Sonora, Mexico. The l ysimeters were irrigated daily with seawater (40 g 1(-1) salts) at rat es ranging from 46-225% of potential evaporation. Biomass and seed yie lds increased with increasing irrigation depth over the range of treat ments. Biomass yields ranged from 13.6-23.1 t DM hd(-1), equivalent to conventional forage crops, on seasonal water application depths of 2. 3-3.8 m, but were markedly lower at lower irrigation depths. Increasin g the irrigation depth lowered the soil solution salinity, resulting i n greater growth and water use, and hence leaching fractions that were nearly even over irrigation treatments, averaging 0.5. Evapo-transpir ation rose in direct proportion to the irrigation depth. Potential eva poration was estimated by site pan evaporation and by the Blaney-Cridd le and Penman models using climatological data; the methods agreed wit hin 15%. The ratio of evapo-transpiration to potential evaporation inc reased over the growing season and approached 1.5 by pan on the highes t irrigation treatment due to the combined effects of high transpirati on and high evaporation from the permanently moist soil surface. The b est field predictor of biomass yield was the salinity of the soil mois ture in the top 15 cm of soil profile, which constitutes the root zone for this crop. Root zone salinity must be kept at 70-75 g 1(-1) for h igh yields. Although irrigation and drainage requirements were high co mpared to conventional crops, seawater irrigation appears to be feasib le in medium sand and could augment crop production along coastal dese rts. The possibility of using this crop for animal production is discu ssed. (C) 1997 Academic Press Limited.