Tolerance of the annual legumes Biserrula pelecinus, Ornithopus sativa, Trifolium spumosum, T. vesiculosum and T. subterraneum to soil acidity

Abstract

The relative tolerance to soil acidity of four annual legumes—biserrula (Biserrula pelecinus), French serradella (Ornithopus sativa), bladder clover (Trifolium spumosum) and arrowleaf clover (T. versiculosum)—was compared to the more widely grown annual legume species, subterranean clover (T. subterraneum). The pH of a Red Kandosol was adjusted with lime to achieve five pH levels ranging from 4.2 to 5.8 in CaCl2. All species were inoculated with an appropriate rhizobia strain and half the treatments received additional mineral nitrogen (N). Shoot weights of all species increased with liming. The pH value required to achieve 90% of maximum herbage yield without N application was c. 4.96–4.98 with 9.3% exchangeable aluminium (Al) for arrowleaf clover, biserrula, French serradella and subterranean clover, but significantly higher at c. 5.3 and only 4.0% exchangeable Al for bladder clover. Root nodule number was insensitive to liming for all species except subterranean clover, which showed a large increase in root nodule number with lime. Comparisons of the percentage reduction in shoot dry weight at the lowest soil pH (4.2), relative to the respective maximum yields with lime in the absence of applied N, showed subterranean clover (39.1%) was the most tolerant species to low pH, followed by French serradella (44.4%), arrowleaf clover (45.2%), biserrula (56.2%) and bladder clover (63.8%).