Acid‐Soil Resistance of Forage Legumes as Assessed by a Soil‐on‐Agar Method

Abstract

Establishment of small-seeded legumes on strongly acid soils can be even more difficult than maintaining those stands once established. Our objectives were to use a soil-based procedure for characterization of acid-soil resistance of small-seeded forage-legumes and to determine the validity of primary root growth and specifically the soil-on-agar technique, using germplasm that varied widely in seed size and acid-soil resistance. We ran four experiments to evaluate 28 cultivars of 15 species. In general, species differences observed were in good agreement with previous knowledge. Large differences in acid-soil resistance, for example among crimson (Trifolium incarnatum L.), white (T. repens L.), and berseem clover (T. alexandrinum L.) were visually obvious. Smaller differences were not as clear but could still be detected statistically; for example, the greater acid-soil resistance of striate [Kummerowia striata (Thunb.) Schindl.] compared with Korean lespedeza [K. stipulacea (Maxim.) Makino]. Relative acid-soil resistance of rose clover (T. hirtum All.) is reported for the first time. Within species, the known greater acid-soil resistance of 'AU Dewey' birdsfoot trefoil (Lotus corniculatus L.), compared with other cultivars of that species, was detected. One major difference between our results and solution culture studies, kura clover (T. ambiguum M. Bieb.) was more acid-soil resistant than white clover. 'Cossack', a kura clover bred from germplasm developed on a high pH soil, was more sensitive to acid-soil stress than several other cultivars. A procedure characterizing primary root growth, the soil-on-agar technique, can do an effective job of evaluating acid-soil resistance of small-seeded legumes.