Calendula officinalis - production potential and crop agronomy in southern England

Interest in Calendula officinalis L. as an industrial oil crop has developed from the discovery that it has a seed-oil content of around 20%, of which up to 60% is calendic acid, a useful industrial feedstock. An EU AIR project vegetable oils with specific fatty acids', is in progress to further develop this and other species. The first 2 years agronomic evaluations of the crop in north west Europe is reported. Nine accessions representing the range of existing genotypes were compared in field experiments. Significant differences in crop maturity, seed, oil and calendic acid content of the oil were recorded. The results suggest the best of current cultivars should produce field yields in the range 2.0-2.5 t ha(-1). Highest yields were produced by early maturing genotypes. Oil content averaged 16.3%, the best accession produced 19.2%. The effect of plant densities between 10 and 80 plants m(-2) on crop development and seed production was investigated. In 1995 there was a significant effect of plant density on yield, which increased up to a plant density of 40 m(-2). Eleven pre-emergence and one post-emergence herbicide were compared for crop tolerance and efficacy of weed control. Only high rate pendimethalin, of the pre-emergence herbicides and post-emergence phenmedipham at full rate caused any adverse crop effects. Trifluralin and metazachlor gave the most consistent weed control over the spectrum experienced: these and a number of other materials significantly reduced weed density. The application of the majority of herbicides significantly increased crop yield. The lack of a safe post-emergence material limits weed control options in the crop. (C) 1998 Elsevier Science B.V.