Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/1998
Publication Date: N/A
Interpretive Summary: Seed yield of many forage legume crops can be modified by regulating soil-water availability. However, the responses to water stress differ for each species, so a single optimal water management strategy is not available for all crops. Birdsfoot trefoil grown for seed under these conditions in maritime western Oregon did not require supplemental irrigation to achieve maximal seed yield. This differs from red and white clover which are two other commonly grown forage legume seed crops in this region. Soil-water conditions favorable for high vegetative development were opposite of the conditions for optimal seed yield water use efficiency.
Technical Abstract: The response of birdsfoot trefoil (Lotus corniculatus L.) to varying levels crop-water stress has not been described when grown in maritime western Oregon, USA. Four single-application treatments varying in water depletion percentage (30 and 60% of field capacity) and replenishment amount 50 and 100% of amount depleted) were applied in 1994 and 1995. A low-stress treatment (LS) that received two to three applications per week of the amount depleted since the last application and a nonirrigated control were also investigated in 1994, 1994, and 1996. Increasing amounts of applied water resulted in increased seasonal evapotranspiration (ETC) with plants grown under LS having the greatest ETC and nonirrigated control plants the least (r=0.91). The fraction of available soil-water used (FAWU) was greatest in nonirrigated plants and least in the LS treatment, and was primarily dependent upon the depletion percentage and secondarily dependent tupon irrigation replacement amount. For nonirrigated conditions, the crop- water requirement ranged from 240 to 255 mm. Soil-water conditions favorable for high vegetative development were opposite of the conditions for optimal seed yield water use efficiency. Unlike other forage legume seed crops birdsfoot trefoil grown under these conditions required minimal or no supplemental irrigation to achieve maximal seed yield.