Water-Use Efficiency and Yield of Sainfoin and Alfalfa
- T. P. Bolger* and
- A. G. Matches
Water is often the primary limiting resource for forage production in semiarid and arid regions. Our objective was to determine yield and water-use efficiency (WUE) of sainfoin (Onobrychis viciifolia Scop.) and alfalfa (Medicago sativa L.) as related to evapotranspiration (ET). Species were grow* in rows under an irrigation gradient. Total seasonal yields were a linear function (r2 = 0.87-0.97) of ET for both species. Maximum sainfoin yields were 85% of alfalfa (20.7 Mg ha-1). Sainfoin produced 58 to 63% of its total yield in the first two harvests as compared to 41 to 46% for alfalfa. When soil water was adequate for spring growth, sainfoin was ready to harvest 2 wk earlier than alfalfa. Total ET of both species was similar. Seasonlong WUE of alfalfa (18.3 kg ha-1 mm-1) was greater than sainfoin (10.7 kg ha-1 mm-'1) in 1986 due to a lack of water in spring when sainfoin yield potential and WUE is highest. In 1987, seasonal WUE of sainfoin and alfalfa was similar (18.2 vs. 16.7 kg ha-1 mm-1), but alfalfa had a smaller evaporation (E) component giving it greater overall WUE and yield. Sainfoin WUE was high in spring and declined in summer. Alfalfa WUE remained high throughout the spring and summer. Both species had low WUE in the fall due to dormancy responses. Differences in leaf area index (LAI) account for differences in E between sainfoin and alfalfa. Sudden death of sainfoin plants in summer was observed under low irrigation; therefore, moderate levels of summer irrigation may be necessary to prevent stand loss. In dryland areas, sainfoin's greatest utility is for early season irrigated pasture or hay.
Copyright © 1990.