Shading and Crop‐Cover Effects on Meadowfoam Oil Yield

Abstract

AbstractMeadowfoam (Limnanthes alba Hartw. ex Benth. subsp. alba cv. Mermaid) seed yield and oil yield vary among years. Consistent high oil yield is needed to encourage profitable commercialization. Field experiments were conducted at Oregon State University in 1987–1988 and 1988–1989 on an Amity silt loam (fine‐silty, mixed, mesic Argiaquic Xeric Argialboll) to test the hypothesis that light and temperature effects before the beginning of rapid elongation of stems influence oil yield through alteration of phytomass (total aboveground dry matter) development. Shade‐cloth and a transparent floating crop cover were used to alter light and temperature, compared to the control. Cover early, cover early plus late, and shade treatments were applied on 22 Jan. 1988 and 24 Jan. 1989. Shade and cover early were removed 29 Mar. 1988 and 28 Mar. 1989; and cover early plus late was removed 12 April 1988 and 11 April 1989. At 2 wk after the beginning of rapid elongation of stems, shaded plants had 24% less phytomass and 28% fewer stems than the control. Shade increased open flowers 27%, seeds per square meter 30%, seed yield 35%, seed oil content 8%, and oil yield 47%. Cover early increased open flowers 23%, seeds per square meter 34%, seed yield 21%, seed oil content 9%, and oil yield 33%. Effects of cover early plus late treatment on crop growth and yield were inconsistent between years. Seed yield improvement by all treatments was associated with fewer primary stems per plant, more flowers that opened, and more seeds per square meter. Genetic manipulation and cultural practices which reduce the number of primary stems per plant and increase the number of flowers opened may lead to increases in oil yield.