Irrigation Effects on Agronomic Characters of Meadowfoam

Meadowfoam (Limnanthes alba Benth.), a winter annual adapted to Mediterranean climates, produces a seed oil that has potential uses in industry. Insufficient water during flowering and seed development of meadowfoam might cause the highly variable seed yields previously experienced. The effects of irrigation on oil yield, seed yield and yield components, plant growth and development, and honey bee (Apis mellifra L.) foraging were determined. Irrigation treatments included: none (control), early irrigation (EI) during flowering, and continued irrigation (CI) from flowering until maturity. The soil was a fine-silty, mixed, mesic Aquultic Argixeroll. Seed yield was not increased with irrigation in 1981, probably because above-average precipitation occurred during May and June, but in 1982 seed yield in the irrigated treatments averaged 32% higher than in the control. Seed yield differences between the El and CI treatments were not significant. Seeds per flower and 1000-seed weights in the irrigated treatments in 1982 were 9 and 5% higher than in the control, respectively. Bee foraging at late flowering was greater in the irrigated treatments than in the control. Greater bee activity in the irrigated treatments may account for more seeds per flower in these treatments than in the control. The seed oil content in the irrigated treatments was significantly lower than in the control; however, meadowfoam in the irrigated treatments in 1982 yielded 29% more total oil than in the control. Compared with the control, irrigated plants were taller in both years and in 1982 produced more dry matter and had a smaller canopy light transmittance. In some years meadowfoam can be successfully grown in Mediterranean climates without irrigation; however, in other years irrigation during flowering and seed development, particularly during flowering, may be required to achieve high seed and oil yields.