Competition for Sulfur by Three Annual-Range Species in Relation to Temperature

Competition for sulfur among Trifolium hirtum, Bromus mollis, and Erodium botrys was studied under adequate (20 lb./acre) and inadequate (5 lb./acre) levels of sulfur and three temperatures (10 degrees, 15.5 degrees, and 21.1 degrees C) under controlled environment conditions. At low levels of sulfur there was little difference in yield or sulfur uptake among the three species with regard to temperature when grown in mono-, di-, or trispecific combinations. In general, both sulfur uptake and yield increased slightly with increasing temperature. At the adequate sulfur level there was a large increase in yield and sulfur uptake of T. hirtum both when grown alone and in combination with other species. This increase was most marked at higher temperatures; it was reduced by the presence of B. mollis, but was unaffected by the presence of E. botrys. The growth and sulfur uptake of B. mollis was increased somewhat by the presence of T. hirtum, but was unaffected by the presence of E. botrys.