Red Clover Seed Production

Abstract

Red clover (Trifolium pratense L.) is an important forage legume grown in North America and Europe. A primary region for world seed production is western Oregon, USA. Stand decline in Oregon seed fields can occur from root rot disease, caused by Fusarium solani (Mart.) Sacc. Increasing soil pH by lime application has been shown to reduce the incidence of Fusarium-caused diseases in numerous other crops. The purpose of this research was to determine the effect and economics of soil pH on red clover seed production and root health. Lime was applied (0, 5.6, and 11.2 Mg ha−1) in autumn 1993 near Corvallis, OR. The effects of normal and delayed spring herbage removal, and first and second-year seed crop age (1994 and 1995) were also examined. Soil pH in May 1996 after planting a wheat (Triticum aestivum L.) rotation crop in the three lime treatments was 5.6, 6.1, and 6.4, respectively. Clover plants in the untreated control were generally chlorotic and shorter than plants in the two lime treatments before herbage removal in spring 1994. First-year seed yields were greater with than without lime, but second year yields were unaffected. Soil pH did not affect clover phytomass after herbage removal in either year, and did not affect straw and grain yields of a wheat rotation crop. Soil pH was correlated with clover root diameter (r = 0.54; P ≤ 0.01), and unlike other crops, was correlated with fusarium root rot severity (r = 0.69; P ≤ 0.001). Within the range of soil pH values examined, and for the combined 2 yr of production, neither lime treatment produced a more economical seed yield than the untreated control. For the range of soil pH conditions, without improved root health, and in the absence of any affect on rotation crop yield, lime application cannot be justified solely for the benefit of red clover seed production.