Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/1999
Publication Date: N/A
Interpretive Summary: Seed crops of the important forage legumes alfalfa, red clover, and white clover require different water management strategies to achieve optimal yields of high quality seeds. However, no information is available describing the response of birdsfoot trefoil, another popular forage legume, to different levels of water stress. The effects of different irrigation timing and replenishment amount treatments on seed yield production was investigated for three crop years. Under the climatic and soil conditions of western Oregon, which are similar to much of Europe, optimal seed yields were achieved by not irrigating this crop. This finding is very different from those of other popular forage legume seed crops and demonstrates the importance of knowing the best management strategies for each specific crop.
Technical Abstract: Forage legume seed crop reproduction can be modified by regulating soil-water availability. However, responses to water stress differ for each species so a single optimal water management strategy is not available for all crops. The response of Lotus corniculatus grown for seed to varying levels of crop-water stress has not been described. The objectives of this study were to determine the effects of irrigation timing and replenishment amount on reproduction and seed yield for three crop years. Six treatments varying in water depletion percentage and replenishment amount were applied in 1994 and 1995. In 1996, only the low-stress (LS) and nonirrigated control (C) treatments were investigated. In the first year of production, maintaining plants under low-stress conditions sustained flowering longer than with limited or no irrigation applications. Flowering was not affected by irrigation in the subsequent two years of production. Total above-ground phytomass production was correlated with the amount of applied irrigation water (r=0.92). All single water application treatments and the C had greater harvested seed yields than the LS treatment. In 1995, all single application treatments had greater harvested SY than the LS treatment. There was no difference between the LS and C treatments in 1995 and 1996. Umbel density and the number of seeds per pod were the primary determinants of total seed yield (r=0.77 and 0.92, respectively). Optimal total seed production was achieved under western Oregon humid temperate marine climatic conditions by not irrigating.