Adaptation of Ornamental Species to an Acid Soil High in Exchangeable Aluminum1

Abstract

Abstract Sixty-nine species of ornamental plants were screened for A1 tolerance in greenhouse pots of acid Tatum subsoil adjusted to different pH levels by liming. Species differed widely in tolerance to the unlimed soil at pH 4.1-4.4. For example, in one experiment the relative top yield on unlimed vs. limed soil (pH 4.3/pH 5.2) was 71% for Dolichos lablab L. (hyacinth bean); 63% for Tropaeolum majus L. (nasturtium); 62% for Cleome spinosa Jacq. (cleome); 59% for Calonyction aculeatum L. (moonflower); 18% for Tagetes erecta L. (marigold); 11% for Cosmos sulphureous Cav. (cosmos); 4% for Calendula officinalis L. (calendula); and 0.8% for Chrysanthemum coronarium L. (garland chrysanthemum). With the exception of cleome, the acid-soil-tolerant species were larger seeded than the sensitive species. Ornamental species also differed in tolerances to neutral-alkaline Tatum soil (pH 7.0-7.2). For example, relative top yields on high lime vs. low lime soil (pH 7.1/5.1) were 89% for marigold, 87% for cleome, 79% for calendula, 78% for hyacinth bean, 54% for nasturtium and 11% for garland chrysanthemum. Ornamental plants were classified according to suitability for strongly acid (pH 4.1-4.4), moderately acid (pH 5.1-5.4) or neutral to alkaline (pH 7.0-7.2) Tatum subsoil.